5.1     Introduction

Your MT2834MR has intelligent features beyond those of the AT 
command set (described in Chapter 3 of this manual). This chapter 
covers these high performance features and commands which provide 
error correction, data compression and speed conversion capabilities. 
Error correction in your modem is via the ITU-T V.42 standard. Data 
compression in the MT2834MR is either MNP Class 5 or ITU-T 
V.42bis. The remainder of this chapter describes these features, and the 
commands to operate them, as well as descriptions of related 
commands.

Error correction is incorporated via the ITU-T V.42 standard. V.42 
actually uses two error correction protocols, LAP-M and MNP Class 3 
& 4. MNP Class 3 & 4 error correction emerged as the industry 
standard among modem manufacturers over the past decade. It's now in 
the public domain, and has been implemented in dozens of modem 
brands that offer error correction with world wide installations in the 
hundreds of thousands of units. LAP-M error correction is similar to 
MNP Class 3 & 4. They both convert asynchronous data characters to a 
synchronous data stream.

The MT2834MR provides two types of data compression: V.42bis and 
MNP Class 5. V.42bis is newer and it requires concurrent error 
correction using LAP-M. V.42bis is a very efficient data compression 
technique that can provide up to a 4-to-1 compression, depending on 
the type of files transmitted. MNP Class 5 data compression requires 
concurrent error correction using MNP Class 3 & 4. It is an older and 
more established standard that offers data compression in the 2-to-1 
range (also dependent on the type of data).

The speed conversion feature allows the modem to operate at one speed 
over the telephone lines and another speed at the RS232C serial port. 
This allows the computer or terminal to communicate with the modem 
at a fixed speed of up to 115,200 bps, while the modem operates at 
various speeds up to 28,800 bps. This is vital if data compression is to 
be effective (your terminal or computer must present data to the phone 
line at a higher speed than which the modem is sending it over the 
phone line).

This chapter also covers commands that control error correction, turn 
data compression on and off and others that are related to high 
performance operation along with the changes in the result codes.

5.2     How V.42 Detects and Corrects Errors

Some of the better known software-based error-correction protocols 
include XMODEM and Kermit (for asynchronous file transfer 
software), X.PC (Tymnet's own asynchronous software protocol), and 
SDLC and HDLC, two popular synchronous protocols common in the 
IBM mainframe environment. V.42 is functionally similar to SDLC and 
HDLC, with some extras.

The main advantage of hardware-based V.42 error correction over these 
software-based protocols is in "throughput". Throughput is the effect 
that the use of the protocol has on the overall data rate. For example, 
V.42 transmissions using a 2400 bps modem have an effective 
throughput of about 2600 bps. The same modem using software-based 
X.PC would have an effective throughput of less than 2400 bps. 
Another way of stating it is that V.42 has an efficiency of about 108%, 
while X.PC has an efficiency of about 91%.

Simply stated, one modem with V.42 sends coded data to another 
modem with V.42, and the receiving modem is able to determine if 
there were any errors. If there were, the receiving modem tells the 
sending modem to resend the errant data until it's correct.

Technically speaking, when using V.42, the "sending" modem uses a 
polynomial function to calculate a 16-bit number which is a function of 
all the data sent in a particular "message" or "block", and then sends 
those sixteen bits at the end of the block. (The "block" can include up to 
256 characters.) The "receiving" V.42 modem, as it is receiving the 
block, calculates its own version of the 16-bit number. Then it 
compares its number with the 16-bit number sent with the block. If the 
numbers are the same, the block is free from errors. If the numbers are 
different, an error has occurred somewhere in the block. That's how 
errors are detected.

Once an error is detected, the receiving modem's V.42 error correction 
is activated. 

For all practical purposes, the result of the V.42 error correction 
protocol is error-free transmission. Using the 16-bit redundancy check, 
it will detect every error which is 16 bits or smaller, with 100% 
probability. As a result, the chances of an error occurring are actually so 
small that you can, in practice, ignore them.

5.3     Data Compression

The MT2834MR has both V.42bis and MNP class 5 data compression. 
ITU-T V.42bis is an international data compression standard which can 
provide data compression of up to four to one in certain types of data. 
MNP class 5 is a proprietary technique for data compression that 
provides a data compression capability of two-to-one.

The MT2834MR must be in error correction mode before it can 
compress data (LAP-M error correction for V.42bis data compression 
or MNP error correction for MNP 5 data compression). By using the #L 
command, you can select which error correction to use.

The type of file transfer protocol used to send and receive data will 
have a big effect on the speed gain due to compression. In general, a 
protocol which uses large data blocks transfers files quicker. For 
example, YMODEM sends 1000 characters per block. It will also help 
to have the serial port of the receiving modem set to the highest 
possible speed (115,200 bps), if the sending modem is set to a lower 
speed.

To achieve a data rate which is higher than the modem baud rate, use 
the modem's speed conversion features by turning Baud Adjust off 
($BA0) and operate the serial port at a higher speed than the modem 
baud rate. For example, the serial port must be set to 4800, 9600, 
19200, 38400, 57600, or 115,200 bps ($SB115200).

To use data compression, the modem must to be driven at full capacity. 
In other words, the data needs to be present at enough volume (file 
transfers or batch operations) and speed to get maximum compression 
benefits. The modem speed conversion features must be used to utilize 
the port at a higher speed than the modem connection speed. Data 
compression works by locating repeated strings of characters and 
repeating these strings using shorter codewords. 

When operating the serial port at a higher speed than the modem baud 
rate, some type of flow control should be used, otherwise data can be 
lost. (See &E4 and &E5 commands.)

To enable data compression, type AT&E15 and hit ENTER; to disable 
data compression, type AT&E14 and hit ENTER.

Note: For data compression to take place, both the answer and originate 
modems must have data compression and error correction enabled.

5.4     MNP Classes

The MNP protocol is divided into several levels, or "Classes". The 
classes you would encounter today in full duplex dial-up in 1200, 2400 
and 9600 bps modems are Classes 2 through 5. When modems 
equipped with MNP start communicating, they will negotiate operation 
to the highest common MNP class between them and operate at that 
level.

5.5     V.42 Mode Select Command (#L)

The V.42 Mode Select command (#L) selects which type of error 
correction your MT2834MR will use for transmissions. The V.42 
standard implements both MNP Class 3 & 4 and LAP-M error 
correction protocols, and by executing one of the #L commands you are 
instructing your MT2834MR how to operate with each protocol. For 
example, the factory default setting (#L0) tells your MT2834MR to 
negotiate the protocol with the remote modem, and to prefer MNP 3 & 
4.

The following details the operation of the #Ln command:

1.      #L0 Command (factory default setting)
	
	The #L0 Command allows a pair of modems to negotiate 
	which V.42 mode (MNP or LAP-M) will be used.
	
	Originate Mode
	a.      If both modems have LAP-M capability, the modems 
		will use LAP-M mode.
	b.      If one or both modems do not have LAP-M capability 
		and both have MNP, the modems will use the MNP.
	
	Answer Mode
	a.      The answering modem will respond to either an MNP 
		Link Request or LAP-M ODP signal, depending 
		on which is issued by the originating 
		Modem.

2.  #L1 Command
	
	The #L1 Command enables MNP error correction and disables 
	LAP-M. This command is for Originate mode only. Answer mode still 
	accepts MNP or LAP-M.

3.  #L2 Command
	
	The #L2 Command enables LAP-M error correction and 
	disables MNP. This command is for Originate mode only. Answer 
	mode still accepts MNP or LAP-M.

4.      #L3 Command
	
	In the above commands, the modems use a two-phase process       
	to establish a V.42 connection ("Detection" to establish 
	whether the remote modem is also error correcting, and 
	"Protocol 			Establishment" to determine 
	parameters and establish the error correction connection). If 
	you know that the other modem is a V.42 error 
	correcting modem, and you wish to use LAP-M, the #L3 
	command to disable the Detection phase and go directly to       
	Protocol Establishment. Both modems must have #L3 in 
	effect.

5.6     Modes of Operation

You can configure your MT2834MR in one of three different V.42 
modes of operation (each mode can be with or without compression). 
These are the Normal, Reliable and Auto-Reliable modes. The modes 
and data compression features are selected with commands covered in 
Section 5.13.

Normal Mode (&E0)

In the Normal mode of operation, the MT2834MR's error correction 
capabilities are disabled, and the modem functions as a normal (non-
error-correcting) modem.

Reliable Mode (&E2)

In Reliable mode, the MT2834MR uses its V.42 error correction 
capabilities during all transmissions. When in Reliable mode, the 
MT2834MR must be connected to another modem with a similar V.42 
protocol activated (MNP or LAPM). If the modems cannot establish a 
V.42 error correction connection, the modem will time out and hang up.

Auto-Reliable Mode (&E1)

In Auto-Reliable mode, the MT2834MR will, during the handshaking 
procedures at the start of the on-line connection, automatically 
determine whether or not the modem with which it is communicating is 
using the error correction. If the MT2834MR determines that the other 
modem is using V.42, it will switch itself into the Reliable (V.42) mode 
of operation. If it is determined that the other modem is not using V.42, 
the MT2834MR will remain in Normal mode.

The method the MT2834MR uses to determine if the V.42 modem 
involves the use of a "Link Request". When the MT2834MR is in Auto-
Reliable mode and originates a call, it goes through normal 
handshaking procedures just like any dial-up modem. After establishing 
the on-line connection, the MT2834MR transmits a Link Request 
message to the answering modem. If the answering modem replies with 
an appropriate V.42  acknowledgment response, the MT2834MR 
switches into Reliable mode. Otherwise, it will stay in Normal mode. 

This V.42 handshaking procedure generally takes about five seconds.
When operating in V.42 Reliable mode, the MT2834MR uses its 
memory, or buffer, to store data as it is received.  During periods of 
error-caused retranmissions or compression slowdowns, this buffer may 
fill up.  To prevent buffer overflow and subsequent loss of data, the 
modem uses flow control to signal the computer attached to its RS232C 
port that the modem buffer is close to being full.  This causes the 
computer to pause in its data transmission until the modem is able to 
empty its buffer sufficiently to accept more data, at which time the 
modem signals the computer that it may resume transmission.

5.7     Introduction to Flow Control

Flow control refers to the techniques used by computer devices to stop 
and restart the flow of data from each other. Flow control is necessary 
so that a device does not receive more data than it can handle. In the 
case of the MT2834MR, there is a need for flow control in both 
directions. Flow control for data passing from your computer to the 
modem is called Modem-Initiated Flow Control and flow control for 
data passing from the modem to your computer is called 
Computer/Terminal-Initiated Pacing.

The MT2834MR supports both hardware and software Modem Initiated 
Flow Control, and, on the Computer/Terminal-Initiated Pacing side, 
supports hardware and software flow control, and a special version used 
by Hewlett Packard compatible systems called ENQ/ACK Pacing. The 
MT2834MR allows hardware and software pacing to be passed through 
the modem to the other end of the link so that your computer or 
terminal can control data start/stop activity through your modem. This 
is called "Xon/Xoff Pass-Through".

To state it simply, "Flow Control" is something the modem does to the 
computer, while "Pacing" is something the computer does to the 
modem.

5.8     Modem-Initiated Flow Control

When operating in the V.42 Reliable mode, the MT2834MR uses its 
memory, or buffer, to store data as it is received. During periods of 
error-caused retransmissions or compression slowdowns, this buffer 
may fill up. To prevent buffer overflow and subsequent loss of data, the 
modem uses flow control to signal the computer attached to its RS232C 
port that the modem buffer is close to being full. This causes the 
computer to pause in its data transmission until the modem is able to 
empty its buffer sufficiently to accept more data, at which time the 
modem signals the computer that it may resume transmission.

The MT2834MR gives you two choices for methods of modem-
initiated flow control. (You also have a third choice, which is to not use 
flow control at all.)  One choice is "Xon/Xoff", which uses special 
characters in the data transmissions. The other is "Hardware Flow 
Control", which uses the CTS output lead on the RS232C interface 
(Clear to Send - Pin 5). Most terminals and computers support one or 
both of these methods.

Xon/Xoff Flow Control (&E5)
	
Xon/Xoff is the most commonly-used method of flow control. 
Under this method, control characters known as "Xon" and "Xoff" are 
inserted by the modem into the data to start and stop the flow of data 
from the computer or terminal to which the modem is attached. Xoff, 
(CTRL-S), stops the flow of data, and Xon, (CTRL-Q), restarts it. With 
regards to binary data, Xoff/Xon flow control is not recommended 
because an Xoff character may be part of the data and would trigger an 
Xoff of the modem or software package, which would halt data flow.

Hardware Flow Control (&E4)
	
With Hardware Flow Control, the modem uses its RS232C 
interface to control the flow of data from the computer or terminal to 
which it is attached. The CTS (Clear to Send) signal on Pin 5 of the 
RS232C interface is brought low to stop the flow of data, and is brought 
high to restart it.
	
When you select Hardware Flow Control as your Modem-
Initiated Flow Control method, you are also selecting it for Pacing. The 
difference between the two, however, is that Modem-Initiated Flow 
Control uses the Pin 5 CTS output signal, while Pacing uses the Pin 4 
RTS input signal. (Refer to Section 5.9.)

Modem commands are used to select the method of flow control used 
by the MT2834MR when its error correction capabilities are used. 
These commands are covered in Section 5.13. If neither method is 
selected, the modem will default to no flow control.

5.9     Terminal/Computer-Initiated Pacing (&E13)

As mentioned earlier, the MT2834MR can initiate flow control by 
issuing Xon/Xoff commands or by toggling the CTS signal on the 
RS232C interface. The modem can also be configured to react to 
similar commands and signals from the computer or terminal to which it 
is attached via the RS232C interface.

We refer to computer or terminal initiated flow control as "Pacing". 
When the modem is set for Pacing On, the modem responds to the 
terminal or computer pacing. When the modem is set for Pacing Off, it 
will ignore pacing.

In order for the MT2834MR to be set for Pacing On, a modem-initiated 
method of flow control must be previously selected. Once this is done, 
the MT2834MR will respond to either Xon/Xoff commands, or to the 
toggling of the RTS (Request to Send) signal on Pin 4 of the RS232C 
interface, depending on what you selected earlier as your Modem-
Initiated Flow Control method.

If you use RTS pacing, be sure that the RTS DIP-Switch is set so that 
RTS is not forced on (see Section 7.3).

5.10    Xon/Xoff Pass-Through (&E7)

So far, you have had three choices to make regarding pacing. You can 
set the modem to respond to Xon/Xoff pacing, or to respond to RTS 
pacing, or you can set the modem to ignore pacing completely.
Another choice you can make (which actually can apply to both pacing 
and modem-initiated flow control, although it applies mainly to pacing) 
is called "Xon/Xoff Pass-Through". This means that if your modem is 
set to respond to Xon/Xoff commands, you can have the modem do one 
of the following.

1.      The modem responds to the Xon and Xoff pacing commands  
	while at the same time allowing these commands to pass  
	through the modem and on to the remote location. We 
	call this "Respond, Pass-Through".

2.      The modem responds to Xon/Xoff pacing, but does not allow 
	the pacing signals to pass through the modem and on to 
	the remote location. We call this "Respond, No Pass-
	Through".

When Xon and Xoff commands are allowed to pass through the 
modem, the computer (or terminal) at the remote site receives these 
commands, and depending on how it is configured, the computer (or 
terminal) may respond to them also.

5.11    Normal Mode Modem Flow Control (&E10 and &E11)

When two MT2834MR's are connected in Normal mode (not using 
error correction), Xon/Xoff can be used to control the flow of data 
between the modems. Flow control can be turned on or off with the 
Normal Mode Modem Flow Control commands. When the modems are 
connected in Reliable mode, a different method of modem flow control 
is used, and the commands for Normal Mode Modem Flow Control are 
ignored.

When using Speed Conversion in Normal mode, you must activate the 
modem's Normal Mode Modem Flow Control. (Speed Conversion is 
explained in Section 5.15.)

5.12    Hewlett Packard ENQ/ACK Pacing (&E9)

If the MT2834MR is used with Hewlett Packard (or similar) equipment 
that employs ENQ/ACK pacing, the modem can be configured to 
respond to ENQ/ACK commands, making it compatible with HP 
systems. Doing so does not effect any other flow control or pacing 
already configured in the modem.

When configured for ENQ/ACK, the ENQ (CTRL-E) and ACK 
(CTRL-F) signals from the HP equipment will be accepted and 
responded to according to Hewlett Packard protocol.

5.13    Compression, Error Correction, Flow Control,    
	Pass Through and Pacing Commands

The MT2834MR has a variety of commands to control its error 
correction and data compression options. These commands are listed 
below. (Remember to precede each command with the AT characters.)
Normal/Auto-Reliable/Reliable Mode Commands:
	
&E0 =   Normal Mode (prevents any error correction mode)
&E1 =   Auto-Reliable Mode* (enables MNP or LAP-M mode)
&E2 =   Reliable Mode (MNP or LAP-M mode only)

Modem-Initiated Flow Control Commands:
	
&E3 =   Disables flow control (no flow control)
&E4  =  Hardware flow control (CTS on/off and RTS on/off)*
&E5 =   Xon/Xoff flow control

Xon/Xoff Pass-Through Commands:
	
&E6 =   Modem responds to Xon/Xoff characters, but does         
	not allow Xon/Xoff characters to pass through to        
	remote site.*
	
&E7 =   Modem responds to Xon/Xoff characters, and allows       
	them to pass through to remote site.

Enq/Ack Pacing Commands:
	
&E8 =     Enq/Ack method of pacing off*
&E9 =     Enq/Ack method of pacing on

Normal Mode Modem Flow Control Commands:
	
&E10 =  Normal Mode Modem Flow Control off*
&E11 =  Normal Mode Modem Flow Control (Xon/Xoff) on
Computer (or Terminal)-Initiated Flow Control(Pacing) Commands:
&E12 =  Pacing off
&E13 =  Pacing on (either RTS on/off or Xon/Xoff depending      
	on the setting of &E4 or &E5).*

*Factory default setting

**The factory default setting for data compression is enabled, but the 
modem will not compress data (&E15) unless &E1 (auto-reliable mode) 
or &E2 (reliable mode) is also selected.

Data Compression Commands:
	
&E14 =  Data Compression disabled
&E15 =  Data Compression enabled**

*Factory default setting

**The factory default setting for data compression is enabled, but the 
modem will not compress data (&E15) unless &E1 (auto-reliable mode) 
or &E2 (reliable mode) is also selected.

5.14    Error Correction Result Codes

When the MT2834MR is operating with error-correction enabled, five 
of its responses are altered, to let you know that you have made a 
connection in Reliable mode. These Result Codes for a V.42 MNP 
connection are listed below:
		
		Verbose                 Terse
	CONNECT RELIABLE                1R
	CONNECT 1200 RELIABLE           5R
	CONNECT 2400 RELIABLE           9R
	CONNECT 4800 RELIABLE           11R
	CONNECT 9600 RELIABLE           12R
	CONNECT 14400 RELIABLE          13R
	CONNECT 19200 RELIABLE          19R
	CONNECT 21600 RELIABLE          21R
	CONNECT 24000 RELIABLE          24R
	CONNECT 26400 RELIABLE          26R
	CONNECT 28800 RELIABLE          28R

The result codes for a V.42 LAP-M connection are listed below: 
		Verbose                 Terse
	CONNECT LAPM                    1L
	CONNECT 1200 LAPM               5L
	CONNECT 2400 LAPM               9L
	CONNECT 4800 LAPM               11L
	CONNECT 9600 LAPM               12L
	CONNECT 14400 LAPM              13L
	CONNECT 19200 LAPM              19L
	CONNECT 21600 LAPM              21L
	CONNECT 24000 LAPM              24L
	CONNECT 26400 LAPM              26L
	CONNECT 28800 LAPM              28L

These responses replace the CONNECT (1), CONNECT 1200 (5), 
CONNECT 2400 (9), CONNECT 4800 (11), CONNECT 9600  (12) 
and CONNECT 14400 (13) responses that the modem uses when in 
Normal mode.

When data compression is enabled, the word COMPRESSED (verbose) 
or letter C (terse) are also added to these responses.

In addition to these responses, the V.42 (Error Correction) LED lights 
when the modem is in error correction (reliable) mode. The V42 LED 
flashes on and off when the modem has data compression enabled.

* MNP 5 data compression can only be activated when using V.42 error 
correction.

5.15    Speed Conversion

This section addresses the speed conversion feature available in the 
MT2834MR. Speed conversion is a necessary part of data compression 
since data must be presented to the phone line faster than it can handle 
data, if compression is to be effective.

Speed conversion allows the MT2834MR to communicate at one speed 
over the phone line, and at another speed at the RS232C interface. The 
speed (also referred to here as "bps," or "baud rate") can be fixed at the 
RS232C interface independently of the baud rate of the on-line 
transmissions.

In addition to data compression, another popular application for speed 
conversion involves an auto-answer MT2834MR connected to a 
computer that does not have autobauding capability. This means that 
the computer must be set at a fixed baud rate, regardless of whether the 
modem is communicating over the phone line at 300, 1200, 2400, 4800, 
9600, 14,400, 19,200, 21,600, 24,000, 26,400, or 28,800 bps. In this 
application, speed conversion allows the modem to match its speed to 
that of an in-calling modem, while at the same time communicating 
with the attached computer through its RS232C port at a fixed baud 
rate, which can be preselected at 300, 1200, 2400, 4800, 9600, 19,200, 
38,400, 57,600, or 115,200 bps.

The flow control and pacing methods used between the computer and 
the modem during speed conversion are the same as those used with the 
V.42 error correction. The two choices (Xon/Xoff or RTS/CTS) are 
selected with the &E commands detailed earlier in this chapter. If you 
are not using the modem's V.42 error correction, you must activate 
modem flow control with a separate command (&E11), as explained 
earlier in Section 5.11.

There are three commands which relate specifically to speed 
conversion. They are Baud Adjust ($BA), Modem Baud Rate ($MB) 
and Serial Port Baud Rate ($SB).

$BA     Baud Adjust

In typical operations, the MT2834MR will do one of two things 
regarding speed. It will automatically match the speed (bps rate or 
"baud rate") of its RS232C interface and phone line transmissions to 
that of the terminal or computer to which it is attached as soon as it 
receives its first AT command. Or, when in auto-answer mode, it will 
match its RS232C and transmission speeds to that of the originating 
modem that called it. This is typical for virtually all of today's dial-up 
modems, and is referred to by various names, such as Auto-Speed or 
Baud Adjust. Here we call it Baud Adjust.

When using speed conversion, set the modem so that it does not adjust 
its speed at the RS232C serial port, even if the modem does adjust its 
line transmission speed. To turn Baud Adjust off, type AT$BA0 (where 
0 is "zero").

Note: Do not be misled by the meaning of turning Baud Adjust "off", 
even though the term "Baud Adjust" sounds like it should mean the 
same thing as "Speed Conversion". It actually means the opposite:

Turning Baud Adjust off turns Speed Conversion on.

Turning Baud Adjust on turns Speed Conversion off.

To turn Baud Adjust on (and Speed Conversion off), enter AT$BA1 
and hit ENTER. The modem will now match its RS232C speed to that 
of the computer, and will adjust its speed to any changes in the 
computer's speed in the originate mode, or to the speed of the 
originating modem when it's in the answer mode. With baud adjust on, 
the speed at which the modem communicates over the phone line is 
always be the same as the speed at which it communicates via its 
RS232C serial port.

$MB     Modem Baud Rate

The $MB command presets the MT2834MR's transmission baud rate 
for originate operations, (i.e., the speed of the modem's transmissions 
over the telephone lines when originating a call). With speed 
conversion, this transmission speed can be a different baud rate than the 
serial port speed.

When the MT2834MR receives (answers) a call from another modem, 
it automatically switches its phone line transmission baud rate to match 
the calling modem. However, if the MT2834MR originates a call to 
another modem that is unable to connect at the baud rate of the 
MT2834MR, the MT2834MR will automatically drop to a lower baud 
rate in an attempt to match the speed of that modem. For example, if the 
MT2834MR is set for 28,800 bps and calls another modem that has a 
top speed of 9600 bps, it will drop to 9600 bps.

To set the Modem Baud Rate, type AT$MBn, where n can be 75 (in 
ITU-T V.23 mode) 300, 1200, 2400, 4800, 9600, 14,400, 19,200, 
24,000, or 28,800 bps as listed below:
	
	AT$MB75 = ITU-T V.23
	AT$MB300 = 300 bps
	AT$MB1200 = 1200 bps
	AT$MB2400 = 2400 bps
	AT$MB4800 = 4800 bps
	AT$MB9600 = 9600 bps
	AT$MB14400 = 14400 bps
	AT$MB19200 = 19200 bps
	AT$MB24000 = 24000 bps
	AT$MB28800 = 28800 bps

The factory default setting is 28,800 bps.

If Baud Adjust is on ($BA1), speed conversion is off, as we discussed 
earlier. This means that the $MB command is also ignored, since it is 
part of speed conversion.

$SB     Serial Port Baud Rate

The $SB command presets the speed of the MT2834MR's serial 
(RS232C) port, in both the originate and answer modes. Speed 
conversion allows you to set this serial port baud rate at a fixed speed of 
up to 115,200 bps, regardless of the modem's transmission speed 
setting.

For this command to work, the modem's Baud Adjust feature must first 
be turned off with the $BA command.

In addition to the MT2834MR's serial port speed being set by this 
command, the default speed at which the modem issues Command 
mode responses (result codes) is also set.

The MT2834MR will accept AT commands  at any speed, regardless of 
the speed preset by  the $SB command. If the modem receives such a 
command at a speed that is different than the preset speed, the modem 
will switch its serial port baud rate to match the new AT command 
speed, although the baud rate value stored by the $SB command will 
remain the same. This provides you with a convenient way to switch the 
serial port speed, while still making it easy to go back to the original 
speed automatically the next time the modem is powered up or reset 
with an ATZ command.

To set the Serial Port Baud Rate, type AT$SBn, where n can be 300, 
1200, 2400, 4800, 9600,19,200, 38,400, 57,600, or 115,200 bps as 
listed below:
	
	AT$SB300 = 300 bps
	AT$SB1200 = 1200 bps
	AT$SB2400 = 2400 bps
	AT$SB4800 = 4800 bps
	AT$SB9600 = 9600 bps
	AT$SB19200 = 19200 bps
	AT$SB38400 = 38400 bps
	AT$SB57600 = 57,600 bps
	AT$SB115200 = 115,200 bps

The factory default setting is 115,200 bps.

5.16    Related Commands

$A      Auto-Reliable Buffering

In Auto-Reliable mode, the modem is given four seconds to establish a 
Reliable connection. After the four seconds, the modem will drop to 
Normal mode. Any data received during this period is normally 
discarded. The $A command is used to cause the modem to buffer 
(save) data that is received during the Auto-Reliable time-out period. 
This data is then output by the modem after the CONNECT message.
Type AT$A0 to discard data received during the Auto Reliable time 
period.

Type AT$A1 to buffer data received during the Auto Reliable time 
period.

The factory default setting is $A0.

&BS     Maximum Block Size

The maximum size of Reliable mode data blocks is controlled with the 
&BS command. MNP Class 3 sends blocks of 1 to 64 characters.  MNP 
Classes 4 and 5 normally send blocks of 1 to 256 characters. Reducing 
the block size for Classes 4 and 5 to 64 characters may give a smoother 
flow of data, and better throughput performance on noisy phone lines. 
Using smaller block sizes over good phone lines may cause a slight loss 
in data throughout speed.

Type AT&BS0 for a maximum transmit block size of 64 characters.

Type AT&BS1 for a maximum transmit block size of 256 characters.

The factory default setting is &BS1.

$F      Enable/Disable Auto-Reliable Fallback Character

In Auto-Reliable mode, the modem is given four seconds to establish a 
Reliable connection. If a single CARRIAGE RETURN is received from 
the remote modem during this four second period, the Auto-Reliable 
modem will assume that the remote modem is not in Reliable mode and 
will drop to a Normal connection. The CARRIAGE RETURN character 
will then be output following the CONNECT message. The 
CARRIAGE RETURN is the only character which will cause the 
modem to drop to Normal mode. Any other data will either be buffered 
or discarded.

The $F command is used to disable this fallback-to-Normal-due-to-
CARRIAGE-RETURN feature. The Auto-Reliable fallback character 
($F) and auto reliable buffering ($A) commands can be used together, 
to cause the modem to buffer all data received up until the CARRIAGE 
RETURN and then drop to Normal mode. All data received will then be 
output following the CONNECT message.

Type AT$F0 to cause the modem to not fall back to normal connect if a 
CARRIAGE RETURN is received.

Type AT$F1 to cause the modem to fall back to normal connect if a 
CARRIAGE RETURN is received.

The factory default setting is $F1.

#P      Parity Selection

The #P command enables the setting of Callback modem parity for the 
prompt message sent by the Callback modem.  AT#P0 selects no parity. 
AT#P1 selects odd parity.  AT#P2 selects even parity.  

The factory default setting is #P0. 

$R      Retransmit Count

If errors are received during a Reliable connection, the modem will re-
send the block of data which contained an error. If another error occurs, 
the block will be re-sent again. The modem counts the number of times 
that a data block is re-sent. If the same block of data is resent 24 times 
and still has not been received properly, the modem will abort the 
connection, as dictated by the AT$R0 command.

This retransmit counter can be disabled with the $R1 command. When 
the retransmit counter is disabled, the modem will keep trying to send 
data and will not abort, not matter how many times the same block is 
resent.

Type AT$R0 to disconnect if the retransmit count is exceeded.

Type AT$R1 to not disconnect due to excessive retransmits.

The factory default setting is $R0.

$E      V.42 Error Correction at 300 bps

At 300 bps, error correction is not normally used. $E1 lets the 
MT2834MR to function in either Normal (&E0), Auto-Reliable (&E1) 
or Reliable (&E2) mode. $E0, which is the factory default setting, 
disables V.42 error correction altogether.

5.17    Summary

This chapter has covered the commands necessary for the MT2834MR 
to operate as a V.42 device. Briefly, we'll summarize these sections 
here. If something here doesn't seem clear, now may be a good time to 
refer to the appropriate section.

V.42 error correction is built into the MT2834MR's hardware, and 
detects virtually 100% of transmission errors, which are usually caused 
by noisy phone lines. When errors are detected, the V.42 protocol 
causes the modem to retransmit the errant data block.

V.42bis and MNP data compression, also built into the MT2834MR's 
hardware, provides an effective throughput higher than the modem's bps 
transmission speed. The amount of increase depends on the type of data 
being transmitted.

The MNP protocol is divided into several "classes", which for our 
purposes are numbered 2 through 5. The MT2834MR uses all of these 
MNP classes, which yields a higher throughput and error free 
transmissions. LAP-M provides another type of error correction.

The MT2834MR can be set for three different modes of operation, 
along with activating data compression in Reliable mode. Normal mode 
disables error correction, Reliable mode enables it, and Auto-Reliable 
mode allows the modem to automatically turn V.42 on when it detects 
its use in another modem.

Flow control methods are used by the MT2834MR to prevent data loss 
from buffer overflow. The modem can both initiate it ("flow control") 
and respond to it ("pacing"), using either Xon/Xoff commands or 
RS232C signaling via CTS (from the modem) or RTS (from the 
computer or terminal). Hewlett Packard ENQ/ACK pacing is also 
supported. If needed, Xon/Xoff commands can be "passed through" the 
modem to a remote computer or terminal.

The MT2834MR's speed conversion feature allows it to operate at one 
speed over the telephone lines and another speed at the RS232C serial 
port. This allows the computer or terminal to communicate with the 
modem at a fixed speed of up to 115,200 bps, while the modem 
operates at various speeds up to 28,800 bps. This ability is vital if data 
compression is to be effective (your terminal or computer must present 
data to the phone line at a higher speed than which the modem is 
sending it over the phone line).

This concludes what is probably the most difficult chapter in this 
manual, covering techniques that bewilder many modem users. If you 
feel that you have mastered these concepts of Error Correction, Data 
Compression, and Speed Conversion, congratulations!

6.1     Introduction

The MT2834MR has four diagnostic test features. The first is an 
automatic self test done each time the modem is powered up. This test 
checks the modem's processor timing and memory chips. The modem's 
front panel LEDs (refer to Chapter 1) display the progress of the self-
test.

The CCITT V.54 Loopback Testing capability supports telephone 
circuit and transmission problem isolation.  If Pin 8 on the RS232 
interface goes high, the MT2834MR goes into analog loopback mode.
The other tests are initiated with the MultiModemManager Software as 
explained in the MultiModemManager Owner's Manual.

7.1     Introduction

There are 3 sets of DIP-Switches and 3 two-position jumpers on the 
MT2834MR card. To remove the MT2834MR modem card from the 
CC4800 rack, pull the ejector levers away from the rack (if necessary 
loosen the retaining screw first), then carefully slide the modem card 
out of the rack.

The DIP-Switches are used to enable or disable various user-selectable 
options. Each DIP-Switch is set to a factory default setting that is useful 
in most applications. Each set of DIP-Switches is labeled with a number 
and can be set to either the UP (marked "OPEN") or Down position.  
The individual switches can easily be set with your fingernail or a 
pencil tip. 

Note:   Before changing any DIP-Switches on the MT2834MR, please 
consult your MultiModemManager software manual.  Many of these 
options can be controlled by the software.

Each of the 3-pin (two-position) jumpers is used to select options. They 
are also pre-set to factory default settings that should be effective for 
your application. The default setting can be easily changed to an option 
setting by removing the shorting plug and replacing in the option 
position. 

The following sections detail the function of each DIP-Switch and 
jumper located on the MT2834MR PC board.

7.2     16-Position DIP-Switches

The MT2834MR PC board contains three pairs of DIP-Switch blocks. 
Each pair of DIP-Switch blocks is numbered 1-12 and 13-16, and each 
pair of DIP-Switch blocks is related to each of the three on-board 
modems.

7.3     16-Position DIP-Switch Settings

Each individual switch, numbered 1-12 and 13-16, and can be set to 
either the Up (marked "OPEN") or Down position. Each of these DIP-
Switches controls the following functions for its corresponding on-
board modem.

7.3.1   DIP-Switches #1 - #12

Switch #1
Forced DTR - "DTR"
(Asynchronous/Synchronous Mode/Leased Line/Dial-Up)
The MT2834MR must have a high DTR signal in order to operate. This 
signal is provided to each modem by the terminal or computer to which 
it is attached, through the RS232/V.24 interface on pin 20. If your 
terminal is not providing DTR to the modem, you can force the DTR 
signal DIP-Switch #1.   
	
DTR function normally                   = Switch #1 UP
DTR forced ON                           = Switch #1 DOWN
(Factory Default Setting = UP)

Switch #2
Flow Control - &E4/&E5
(Asynchronous Mode/Leased Line/Dial-Up)
With Hardware Flow control, the modem uses its RS232C/V.24 
interface to control the flow of data from the computer or terminal to 
which it is attached. CTS signal on Pin 5 of the RS232C/V.24 is 
brought low to stop the flow of data, and is brought high to restart it. 
Place DIP-Switch #2 in the UP position to enable Hardware Flow 
control (&E4). Xon/Xoff Flow control (&E5) is another method of flow 
control in which Xon/Xoff characters in the data dictates the start and 
stop of data flow from the computer or terminal. Place DIP-Switch #2 
in the DOWN position to enable Xon/Xoff Flow control.
	
Hardware Flow Control (&E4)     = Switch #2 UP
Xon/Xoff Flow control (&E5)     = Switch #2 DOWN
(Factory Default Setting = UP)

Switch #2
SDLC/BSC Selection
(Synchronous Mode/Leased Line/Dial-Up)
Synchronous Data Link Control (SDLC) and Binary Synchronous 
Control (BSC) are two error correction protocols used in the IBM 
Mainframe environment. Place DIP-Switch #2 in the UP position to 
select SDLC mode. Place DIP-Switch #2 in the DOWN position for 
BSC mode.
	
SDLC Mode                       = Switch #2 UP
BSC Mode                        = Switch #2 DOWN
(Factory Default Setting = UP)

Switch #3
Enable/Suppress Responses - "Q"
(Asynchronous Mode/Dial-Up)
In some applications in Asynchronous mode, you may want to suppress 
all responses from the modem. Place DIP-Switch #3 in the DOWN 
position to enable result code responses (Q0). Place DIP-Switch #3 in 
the UP position for answer mode without responses and echo off, (but 
with originate still intelligent)(Q2).

Enable Responses: Originate/Answer (Q0) = Switch#3 DOWN         
Suppress Responses: Answer (Q2) = Switch #3 UP 
(Factory Default Setting = DOWN)

Switch #3
dB Transmission Levels
(Asynchronous/Synchronous Mode/Leased Line)
The MT2834MR can adjust to dB transmission levels required by some 
phone carriers. With DIP-Switch #3 in the DOWN position, the 
MT2834MR transmits at 0 db. With DIP-Switch #3 in the UP position, 
transmission is at -10dB.

0dB Transmission                = Switch #3 DOWN
-10dB Transmission              = Switch #3 UP
(Factory Default Setting = UP)

Note: dB transmission levels on International models may be different 
from those values shown above.

Note: Switch #3 has no effect in leased line mode in the MT2834MRK.

Switch #4
AS/400 Mode
(Synchronous Mode/Leased Line/Dial-Up)
The MT2834MR can function in an IBM AS/400 environment. Place 
DIP-Switch #4 in the DOWN position to cause the MT2834MR to 
operate via IBM command set.

Place DIP-Switch #4 in the UP position to disable AS/400 mode 

Note: The MT2834MR must be in Command mode to allow AS/400 
mode operation).

AS/400 Mode Enabled                     = Switch #4 DOWN
AS/400 Mode Disabled                    = Switch #4 UP
(Factory Default Setting = UP)

Switch #4
UNIX UUCP Spoofing
(Asynchronous Mode/Leased Line/Dial-Up)
The MT2834MR can be used with UNIX equipment which employs 
ACK flow control to monitor data integrity. The MT2834MR can do 
UUCP "spoofing", where the modem is able to generate ACKs at the 
DTE interface. Data is then transmitted more time-efficiently, because 
the delay of waiting for data to be received then for the ACK to be 
returned at the remote end is eliminated. Place DIP-Switch #4 in the 
DOWN position to enable UUCP spoofing.
	
UUCP Spoofing Enabled           = Switch #4 DOWN
UUCP Spoofing Disabled          = Switch #4 UP
(Factory Default Setting = UP)

Switch #5
Disable Auto-Answer - "Ans" 
(Asynchronous Mode/Synchronous Mode/Dial-Up)
In some originate-only applications, you may wish to disable the 
MT2834MR's automatic answering capabilities. This may be true if you 
have a telephone set attached to a modem and wish to receive voice 
calls that you yourself would answer instead of the modem.
	
Auto-Answer Enabled             = Switch #5 UP
Auto-Answer Disabled            = Switch #5 DOWN
(Factory Default Setting = UP)

Switch #5
Originate/Answer Mode
(Asynchronous/Synchronous Mode/Leased Line)
The MT2834MR can function in either Originate mode or Answer 
mode. To enable Answer mode, place DIP-Switch #5 in the UP 
position. To enable Originate mode, place DIP-Switch #5 in the 
DOWN position.

Origination Enabled             = Switch #5 DOWN
Answer Enabled                  = Switch #5 UP
(Factory Default Setting = UP)

Switch #6
Maximum Throughput Setting
(Asynchronous Mode/Leased Line/Dial-Up)
In some applications, you may want to dial into services with maximum 
throughput on. Other applications require maximum throughput off 
(e.g., service not supporting error correction, or the V.42 handshake 
interferes with logon sequence). Switch #6 controls three important 
parameters, which in effect enable or disable maximum throughput 
(error correction, speed conversion and serial port speed).
 
Maximum Throughput Enabled              = Switch #6 UP
Maximum Throughput Disabled             = Switch #6 DOWN
(Factory Default Setting = UP)

Switch #6
Slave Clocking
(Synchronous Mode/Leased Line/Dial-Up)
In Synchronous mode, DIP-Switch #6 controls the timing at the receive 
clock. The originating side, in effect, adjusts to the timing at the remote 
("slave") side.
	
Slave Clocking Enabled                  = Switch #6 DOWN
Slave Clocking Disabled         = Switch #6 UP
(Factory Default Setting = UP)

Switch #7
Request To Send Forced - "RTS" 
(Asynchronous/Synchronous Mode/Leased Line/Dial-Up)
If your computer or terminal uses RTS-CTS protocol (normally used in 
synchronous applications, but also if you are using hardware pacing for 
V.42 error correction or speed conversion), you may want to switch 
RTS to function independent of CTS (DIP-Switch #7 UP). For most 
applications, especially asynchronous, Switch #7 should be set so that 
RTS is forced on (DIP-Switch #7 DOWN).
	
RTS functions Normally                  = Switch #7 UP
RTS forced ON                           = Switch #7 DOWN
(Factory Default Setting = DOWN)

Switch #8
Enable/Disable Command Mode - "Com"
(Asynchronous/Synchronous Mode/Leased/Dial-Up)
In some applications you may want to disable Command mode so that 
the modem will not recognize or react to AT or any other commands. 
This may be true in strictly auto-answer applications where no call 
origination will be required. DIP-Switch #8 enables or disables the 
modem's ability to recognize Command mode characters. The factory 
default setting is Command mode enabled.
	
Disable Command Mode            = Switch #8 UP
Enable Command Mode             = Switch #8 DOWN
(Factory Default Setting = DOWN)

Switch #9
No function.

Switch #10
Leased Line/Dial-Up Operation - "DDD"
(Asynchronous/Synchronous Mode/Leased Line/Dial-Up)
The MT2834MR can operate in both leased-line or dial-up modes. This 
switch controls leased-line/dial-up operation. For dial-up operation, 
place DIP-Switch #10 in the UP position. For leased-line operation, 
place DIP-Switch #10 in the DOWN position.
	
Dial-Up Operation               = Switch #10 UP
Leased Line Operation                   = Switch #10 DOWN
(Factory Default Setting = UP)

Switch #11
"AT" Responses/Multi-Tech Responses
(Asynchronous Mode/Leased Line/Dial-Up)
In Asynchronous mode (DIP-Switch #12 DOWN), the MT2834MR 
responds with result codes according to the Multi-Tech command 
response set or with the "AT" command response set (DIP-Switch #11 
in the UP position). The &Q command performs the same function of 
choosing AT or Multi-Tech responses and is explained further in 
Chapter 5.
	
"AT" Responses (&Q1)                    = Switch #11 UP
Multi-Tech Responses (&Q0)              = Switch #11 DOWN
(Factory Default Setting = DOWN)

For more information on Result Codes, refer to Chapter 3.

Switch #11
Internal/External Clocking
(Synchronous Mode/Leased Line/Dial-Up)
With the MT2834MR in Synchronous Mode, the transmit clock can be 
supplied by the DTE on pin 24 of the RS232C/V.24 interface by DIP-
Switch #11 positioned UP. DIP-Switch #11 in the DOWN position 
enables the DCE to control clocking.
	
External Clock (pin 24)                 = Switch #11 UP
Internal Clock (pins 15/17)             = Switch #11 DOWN
(Factory Default Setting = DOWN)

Switch #12
Asynchronous/Synchronous Operation - "Sync"
(Asynchronous/Synchronous Mode/Leased Line/Dial-Up)
The MT2834MR can operate in both asynchronous mode and 
synchronous mode. When in synchronous mode, start and stop bits are 
eliminated. The modem's internal clock circuits on the RS232C/V.24 
pins 15 and 17, are activated. The MT2834MR's Command Mode will 
not be accessible in the synchronous mode. For synchronous operation, 
you may want to set the RTS forcing and CTS forcing DIP-Switches so 
that both of signals act normally (not forced on).
	
Synchronous Operation                   = Switch #12 UP
Asynchronous Operation                  = Switch #12 DOWN
(Factory Default Setting = DOWN)

7.3.2   DIP-Switches #13 - #16

Switches #13 and #14 - Speed Selection
DIP-Switches #13 and #14 are used for speed selection (mainly in call 
origination leased line applications).
				
				DIP-Switch
28800 bps Operation             #13     #14
				UP      UP

19200 bps Operation             #13     #14
				DOWN    UP

14400 bps Operation             #13     #14
				UP      DOWN

9600 bps Operation              #13     #14
				DOWN    DOWN

NOTE:   The modem baud rate command, $MB, overrides the                 
	setting of DIP-Switches #13 - #14.

Switch #15
Carrier Detect/DSR Source - "DSR"
(Asynchronous/Synchronous Mode/Dial-Up/Leased Line)
Some terminals react in unusual ways to the toggling of the Carrier 
Detect (CD - RS232C/V.24 pin 6) signals. The most common symptom 
is that the modem will not respond to commands, or will not echo 
characters. In these cases, force these two signals On in order for the 
terminal to communicate properly with the modem when the modem is 
in Command mode by placing DIP-Switch #15 in the DOWN position. 
With Switch #15 UP, the state of the CD and DSR signals depend on 
the On-Line status.
		
CD and DSR normal = Switch #15 UP
CD and DSR forced On = Switch #15 DOWN
(Factory Default Setting = UP)

Switch #16
2-Wire/4-Wire Leased Line
(Asynchronous/Synchronous Mode/Leased Line)
		
2-Wire Leased Line = Switch #16 UP
4-Wire Leased Line = Switch #16 DOWN
(Factory Default Setting = DOWN)

7.4     Jumper Settings

The MT2834MR has three two-position jumpers (one for each modem) 
for OOS and service.  Each set of OOS jumpers defines pin 25 of the 
RS232C/D interface as an input (OOS) or an output (Test Mode) for 
one of the three modems. Each is set to a default of OOS (U.S.); 
international models have a default setting of Test Mode.  

There is also a factory-set selection for MI/MIC (modified dial-up 
phone line interface that allows dialing by an external device such as an 
801 Dialer, computer or PBX/CBX system dialer).

7.4.1   ATEST/AV54 Jumper (S105)

Jumper S105 sets pin 25 of Modem A as input (OOS) for the default 
and output (Test Mode) as the option setting on domestic (US) 
modems. On international modems, Jumper S105 sets pin 25 of Modem 
A as input (OOS) for the option, and output (Test Mode) as the default 
setting.

7.4.2   BTEST/BV54 Jumper (S205)

Jumper S205 sets pin 25 of Modem B as input (OOS) for the default 
and output (Test Mode) as the option setting on domestic (US) 
modems. On international modems, Jumper S205 sets pin 25 of Modem 
B as input (OOS) for the option, and output (Test Mode) as the default 
setting.

7.4.3   CTEST/CV54 Jumper (S305)

Jumper S305 sets pin 25 of Modem C as input (OOS) for the default 
and output (Test Mode) as the option setting on domestic (US) 
modems. On international modems, Jumper S305 sets pin 25 of Modem 
C as input (OOS) for the option, and output (Test Mode) as the default 
setting.

Appendix B
Dial Pulse and Tone-Dial Frequencies

DIAL PULSES

If the digit 2 is pulse dialed, followed by the digit 
1. Each pulse consists of an A mSec. open and a B mSec. closed, where 
A will be either 60 or 67 mSec and B will be either 40 or 33 mSec., for 
a total of 100 mSec. per pulse, or a rate of 10 pulses per second. The 
interdigital pause time is 800 mSec. The pulse ratios are controlled by 
the &P command*.

TONE DIAL FREQUENCIES

The tone-dialing method combines two frequencies for each of the 
twelve digits found on a Touch Tone dial pad. This method is referred 
to as Dual-Tone Multi-Frequency (DTMF) dialing.  

The four horizontal rows on a Touch-Tone keypad use the four low 
frequencies (697, 770, 852, 941 Hz), while the three vertical columns 
use the three high frequencies (1209, 1336, 1477 Hz). The generally 
accepted tone frequency tolerance is +0.02%.

*Not applicable in BABT models

For example, the digit 4 would be dialed by combining two tone 
frequencies. It would use the frequency 770 Hz from the second row, 
and the frequency 1209 Hz from the first column. In another example, 
the digit 9 would be dialed with the tone frequencies of 852 Hz and 
1477 Hz.

The extended DTMF characters (A, B, C, D) are the high-end 
frequencies (1633 Hz) defined on some telephone sets with a fourth 
vertical column of buttons. This fourth column provides for extended 
PBX control functions; the actual functions provided are dependent on 
the PBX manaufacturer's implementation and feature set.

Appendix C
DIP-Switch Summary

DIP-Switch      Condition       Effect                        
Asynchronous Mode

#1              *UP             DTR dependent on interface
		Down            DTR force On at all times
#2              *UP             Hardware Flow Control
		Down            Xon/Xoff Flow Control
#3              UP              Disable Command Mode Response 
				(dial up)
		*Down           Enable Command Mode Response 
				(dial up)
#3              UP              -10 dB Transmission (leased line)
		*Down           0 dB Transmission (leased line)

Note: dB transmission levels on International models may be different 
from those values shown above.

Note: Switch #3 has no effect in leased line mode in the MT2834MRK.

#4              *UP             UUCP Spoofing Disabled
		Down            UUCP Spoofing Enabled
#5              *UP             Enable Automatic Answer (dial up)
		Down            Disable Automatic Answer (dial up)
#5              *UP             Answer Mode (leased line) 
		Down            Originate Mode (leased line)
#6              *UP             Max throughput Enabled
		Down            Max throughput Disabled
#7              UP              RTS dependent on Interface
		*Down           RTS forced On at all times
#8              UP              Disable Command Mode
		*Down           Enable Command Mode
#9              UP              No function
		*Down                   
#10             *UP             Dial-Up Operation
		Down            Leased Line Operation
#11             UP              "AT" Responses
		*Down           Multi-Tech Responses
#12             UP              Synchronous Mode
		*Down           Asynchronous Mode

See page C-3 for information on DIP-Switches #13 - #16

DIP-Switch      Condition       Effect
Synchronous Mode

#1              *UP             DTR Dependent On interface
		Down            DTR forced On at all times
#2              *UP             SDLC Mode On
		Down            BSC Mode On
#3              UP              Disable Command Mode Response 
				(dial up)
		*Down           Enable Command Mode Response 
				(dial up)
#3              UP              -10 dB Transmission (leased line)
		*Down           0 dB Transmission (leased line)

Note: dB transmission levels on International models may be different 
from those values shown above.

Note: Switch #3 has no effect in leased line mode in the MT2834MRK.

#4              *UP             AS/400 Mode Disabled
		Down            AS/400 Enabled
#5              *UP             Enable Automatic Answer (dial up)
		Down            Disable Automatic Answer (dial up)
#5              *UP             Answer Mode (leased line) 
		Down            Originate Mode (leased line)
#6              *UP             Slave Clocking Disabled
		Down            Slave Clocking Enabled
#7              UP              RTS Dependent on interface
		*Down           RTS Forced On at all times
#8              UP              Disable Command Mode
		*Down           Enable Command Mode
#9              UP              No function
		*Down           
#10             *UP             Dial-Up Operation       
		Down            Leased Line Operation
#11             UP              External Clock 
		*Down           Internal Clock 
#12             UP              Synchronous Mode
		*Down           Asynchronous Mode


Appendix D
Result Code Summary

DIGIT   WORDS           EFFECT
"Multi-Tech" Result Codes*
	
0       OK              Command was executed without 
			error; ready for next command.
1       CONNECT         Modem has detected carrier and gone on-line.
2       RING            Modem has detected ring caused by 
			incoming call.
3       NO CARRIER      No carrier signal has been detected within allowed 
			time.
4       ERROR           Error in Command line (too many, or invalid 
			characters).
5       CONNECT 1200    Modem has detected carrier at 1200 bps and gone 
			on-line.
6       NO DIAL TONE    No dial tone has been detected.
7       BUSY            A busy signal has been detected.
8       NO ANSWER       Remote system did not answer.
9       CONNECT 2400    Modem has detected carrier at 2400 bps and gone 
			on-line.
11      CONNECT 4800    Modem has detected carrier at 4800 bps and gone 
			on-line.
12      CONNECT 9600    Modem has detected carrier at 9600 bps and gone 
			on-line.
13      CONNECT 14400   Modem has detected carrier at 14400 bps and gone 
			on-line.
19      CONNECT 19200   Modem has detected carrier at 19200 bps and gone 
			on-line.
21      CONNECT 21600   Modem has detected carrier at 21600 bps and gone 
			on-line. 
23      CONNECT 1275    Modem is connected in V.23 mode.
24      CONNECT 24000   Modem has detected carrier at 24000 bps and gone 
			on-line.
26      CONNECT 26400   Modem has detected carrier at 26400 bps and gone 
			on-line.
28      CONNECT 28800   Modem has detected carrier at 28800 bps and gone 
			on-line.

Note: If the MT2834MR is used in MNP Reliable mode, the following 
Result Codes change:
	1R      CONNECT RELIABLE
	5R      CONNECT 1200 RELIABLE
	9R      CONNECT 2400 RELIABLE
	11R     CONNECT 4800 RELIABLE
	12R     CONNECT 9600 RELIABLE
	13R     CONNECT 14400 RELIABLE
	19R     CONNECT 19200 RELIABLE
	21R     CONNECT 21600 RELIABLE
	24R     CONNECT 24000 RELIABLE
	26R     CONNECT 26400 RELIABLE
	28R     CONNECT 28800 RELIABLE

*See Note 2 for "AT Command Set Result Codes".

Note: If the MT2834MR used in LAP-M Reliable mode, the following 
Result  Codes change:
	
	1L      Connect LAPM
	5L      Connect 1200 LAPM
	9L      Connect 2400 LAPM
	10L     Connect 4800 LAPM
	12L     Connect 9600 LAPM
	13L     Connect 14400 LAPM
	19L     CONNECT 19200 LAPM
	21L     CONNECT 21600 LAPM
	24L     CONNECT 24000 LAPM
	26L     CONNECT 26400 LAPM
	28L     CONNECT 28800 LAPM

Note 1: If  the MT2834MR is used with data compression, the word 
COMPRESSED or the letter  C is added to the result codes.

Note 2: If Standard AT Command Set 2400 Result Codes are selected 
with &Q command, the following Result Codes change:
	
	9       (not used)
	10      CONNECT 2400    Modem has detected carrier at 2400 
		bps and gone on-line.

Appendix E
S-Register Summary

REGISTER        UNIT    RANGE   DEFAULT DESCRIPTION
S0              1 ring  0-255   1       Sets number of rings until 
					modem answers.

S1              1 ring  0-255   0       Counts rings which have 
					occurred.

S2              ASCII   0-127   43      Sets Escape Code character
					(default is plus + sign).

S3              ASCII   0-127   13      Sets character recognized as      
					RETURN (default is CTRL-M).

S4              ASCII   0-127   10      Sets character recognized 
					as LINE FEED (default is CTRL-J).

S5              ASCII   0-32    8       Sets character recognized as
			127             BACKSPACE (default is CTRL-H).

S6              1 sec.  2-255   2       Defines wait-time for dial tone.
			4-7*    4*              

S7              1 sec.  1-255   45      Defines how long modem
			1-45*           will wait for carrier before
					aborting call.

S8              1 sec.  0-255   2       Sets pause time caused by a
			4-7*    4*      comma character in a dial
					command.

S9              100mSec 1-255   6       Sets Carrier Detect response time.

S10             100mSec 1-255   7       Sets delay time between when
					carrier is lost and when modem
					disconnects.

S11             1 mSec  1-255   70      Sets time duration of and
			80-255* 80*     spacing between tones in
					tone-dialing.

S13             ASCII   0-127   37      Defines Remote Configuration
					Escape Character

S17             10mSec 0-2500  250mSec  Defines length of break time seconds 
					(space) to PC.

S18             30 min. 10-255  30      Modem monitors leased line to                 
					see if it's 
					operational and will try                              
					to restore leased line connection.
	
S19             1 min   0-255   1       Dial-backup timer used for 
					timing dial-line back-up.
	
S24             50 mSec 0-255   20      Sets DSR/CTS/CD dropout
					time. The default (20) equals                                             
					one second.
	
S25             100mSec 0-255   0       Sets DTR dropout time.
					The default (0) default equals 50 
					mSec.
	
S30             min      0-255  0       Inactivity timer used to disconnect 
					modem.
	
S32             1 sec.  0-255   2 mSec  S32 sets the time that the 
					modem waits for <CR> to be 
					entered during Escape Sequence 
					execution.
	
S34             ASCII   0-60    10      Sets the number of command 
					characters allowed for Escape 
					Sequence entry.
	
S36             1 sec   0-255   0       When DTR is low for S36         
					seconds, the modem sets OOS.
	
S37             1 sec   5-255   5       When DTR is high for S37 
					seconds, the modem clears OOS.

* Values for MT2834MRK units only. 


Appendix F
Command Summary

COMMAND VALUES          DESCRIPTION
AT                      Attention Code that precedes most command 
			strings except A/, A: and Escape Codes.

RETURN                  Pressing RETURN key executes most commands.

A                       Answer call, even if no ring present.

A/                      Repeat last command.  Do not precede this       
			command with AT. Do not hit ENTER to execute.

&A                      Answerback (proprietary feature)

A:**                    Continuous redial (10 redials in DOC units) 
			of last number until answered.

$An     n = 0 or 1   ***$A0 discards data during auto-reliable time
			period.
			$A1 buffers data during auto-reliable time
			period.
#An     n = 0 thru 3 ***#A0 selects initial handshake at 28,800 to                             
			24,000 to 21,600 to 19,200 to 16,800 to                                  
			14,400 to 12,000 to 9600 to 4800 to 2400 to                            
			1200 to 300 bps.
			#A1 selects initail handshake at 28,800 bps     
			only.
			#A2 selects initail handshake at 28,800 to                          
			24,000 to 21,600 to 19,200 to 14,400 to                         
			9600 to 4800 bps only.
			#A3 selects initial handshake at 2400 to 
			1200 to 300 bps only.

%ASn    n = 0 or 1   ***%AS0 disables IBM AS/400 Support
			%AS1 enables IBM AS/400 Support

Bn**    n = 0 or 1      B0 selects ITU-T answer tone at 300 baud.
		     ***B1 selects Bell answer tone at 300 baud.

&Bn     n = 0 or 1   ***&B0 means normal transmit buffer size.
			&B1 means reduced transmit buffer size.

&BSn    n = 0 or 1      &BS0 means maximum transmit block size of
			64 characters.
		     ***&BS1 means maximum transmit block size of
			256 characters.

$BAn    n = 0 or 1   ***$BA0 means Baud Adjust is off, speed conversion is on.
			$BA1 means Baud Adjust is on, speed conversion is off.

&Cn     n = 0, 1,       &C0 forces Carrier Detect on.
	2, or 4      ***&C1 lets Carrier Detect act normally.
			&C2 lets Carrier Detect drop S24 time on
			disconnect.
			&C4 resets modem when Carrier Detect drops.

*Cn     n=0 thru 2   ****C0 turns off Caller ID detection
			*C1 turns on Caller ID detection for the MMM
			*C2 turns on Caller ID reporting on the 
			serial port by the MMM

Ds       s = phone #    Dial a telephone number "s," where s may
			include up to 60 digits or T, P, R, comma
			and ; characters.

DsDn    s = phone #     Store telephone number. To store, phone d = 0 thru 9                    
			number "s" is entered and followed by N                                       and then 
			Directory Number "d".

&Dn     n = 0 thru 3    &D0 DTR is ignored
			&D1 means modem returns to command mode.
		     ***&D2 lets modem react to DTR normally.
			&D3 causes modem to reset to modem
			default parameters.

$Dn     n = 0 or 1   ***$D0 disables DTR Dialing.
			$D1 enables DTR Dialing.

En      n = 0 or 1      E0 means do not echo Command Mode Character.
		     ***E1 means do echo Command Mode Characters.

$En     n = 0 or 1   ***$E0 disables 300 baud error correction.
			$E1 enables 300 baud error correction.

&En     n = 0 thru 15   &E0 means V.42 Normal Mode.
		     ***&E1 means V.42 Auto-reliable Mode.
			&E2 means V.42 Reliable Mode.
			&E3 means no modem-initiated flow control.
		     ***&E4 means CTS modem-initiated flow control.
			&E5 means Xon/Xoff modem-initiated flow
			control.
		     ***&E6 means Xon/Xoff not passed through.
			&E7 means Xon/Xoff passed through.
		     ***&E8 means Enq/Ack pacing off.
			&E9 means Enq/Ack pacing on.
		     ***&E10 means Normal Mode flow control off.
			&E11 means Normal Mode flow control on.
			&E12 means Pacing off.
		     ***&E13 means Pacing on.
			&E14 means data compression disabled.
		     ***&E15 means data compression enabled.

$EBn    n = 0 or 1   ***$EB0 enables 10 bit mode.
			$EB1 enables 11 bit mode.

%En     n=0 thru 5      % E0 = Modem Won't Escape.
		     ***% E1 = +++ Method (default setting).
			% E2 = Break Method.
			% E3 = Either +++ or Break Method.
		     ***% E4 = Disables "OK" Response to +++
			Escape Method.
			% E5 = Enables "OK" Response to +++
			Escape Method.

#Fn     n = 0, 1, 8,    #F0 means no fallback when on-line.
	or 9            #F1 means fallback from 14400 to 4800 bps
			when on-line.
		     ***#F2 means fallback to 4800 bps from 
			14.4K/fall forward when line improves.

&F                      &F loads factory default values from ROM.
		     ***&F8 loads factory defaults after &F.
			&F9 loads RAM defaults after &F.

$Fn     n = 0 or 1      $F0 means do not fall back to normal
			connect if CR received.
		     ***$F1 means fall back to normal connect if CR
			received.

&Gn**   n = 0, 1 or 2***&G0 turns off ITU-T guard tones.
			&G1 turns on ITU-T 550 Hz guard tone.
			&G2 turns on ITU-T 1800 Hz guard tone.

Hn      n = 0 or 1      H0 means Hang Up (go on hook).
			H1 means Go Off Hook.

$Hn     n = 1 thru 3    $H1 brings up Help Screen #1. 
			$H2 brings up Help Screen #2.
			$H3 brings up Help Screen #3.

In      n = 0 or 1      I0 requests modem ID #.
			I1 requests firmware revision #.

L                       Lists all stored telephone numbers in memory.

L5                      L5 lists all current operating parameters.

L6                      L6 lists all current S-Register values.

L7                      L7 lists additional parameters.

L8                      L8 lists on-line diagnostics

#Ln     n = 0 thru 3 ***#L0 means modems negotiate V.42 Mode.
			#L1 means MNP on and LAP-M off.
			#L2 means LAP-M on and MNP off.
			#L3 means no detection phase but go 
			directly to LAP-M.

&Ln     n = 0,1,2A,     &L0 selects Dial-up line operation
	2D,4A,4D        &L1 allows a single attempt at 
			leased line connection
			&L2A selects 2 wire Answer mode operation
			&L2D selects 2 wire Originate mode operation
			&L4A selects 4 wire Answer mode operation
			&L4D selects 4 wire Originate mode operation

&Mn     n = 0 or 1   ***&M0 means Async when on-line.
			&M1 means Sync when on-line.

$MIn**  n = 0 or 1   ***$MI0 disables MI/MIC option (**)
			$MI1 enables MI/MIC option (**)

$MBn    n = speed       $MB75 selects ITU-T V.23 mode.
			$MB300 selects 300 bps on-line. 
			$MB1200 selects 1200 bps on-line.
			$MB2400 selects 2400 bps on-line.
			$MB4800 selects 4800 bps on-line.
			$MB9600 selects 9600 bps on-line.
			$MB14400 selects 14400 bps on-line.
			$MB19200 selects 19200 bps on-line.
			$MB24000 selects 24000 bps on-line.
		     ***$MB28800 selects 28800 bps on-line.

Nd      d = 0 thru 9    Dial stored telephone number "d". 
			Do not include the letter D with this command.

NdNe    d = 0 thru 9    Number Linking.  If first number dialed is                                  
	e = any other   busy, another stored number may be number                 
	    number 0    automatically dialed. For example, stored                
	    thru 9      number "d" is dialed, and if busy, stored               
			number "e" is dialed.

O                       Exit Command Mode and go into On-Line Mode.

P                    ***Modem will pulse-dial numbers following the P.

&Pn**   n = 0 or 1   ***&P0 means 60-40 pulse ratio.
			&P1 means 67-33 pulse ratio.

#Pn     n=0 thru 2   ***#P0 means no parity.
			#P1 means odd parity.
			#P2 means even parity.

Qn      n = 0 or 1   ***Q0 means Result Codes sent.
			Q1 means Result Codes will be suppressed
			(quiet).
			Q2 means Dumb Answer Mode.

&Qn     n = 0 or 1   ***&Q0 selects Multi-Tech command set.
			&Q1 selects AT command set.

Rn      n = 0 or 1   ***R0 means modem will not reverse modes.
			R1 means modem will reverse modes.

&Rn     n = 0, 1 or 2   &R0 lets Clear to Send act normally.
		     ***&R1 forces Clear to Send on.
			&R2 drops for 1 second on disconnect.

&RFn    n = 0 or 1      &RF0 selects CTS follows RTS.
		     ***&RF1 selects CTS to act independently.

$Rn     n = 0 or 1   ***$R0 means disconnect after 12 retransmits.
			$R1 means do not disconnect after 12
			retransmits.

Sr=n    r = 0 thru 11,  Sets value of Register "r" to value of "n",  
	13, 17-19, 24,  where "n" is entered in Decimal format.
	25, 30, 32, 34

Sr?     r = 0 thru 11,  Reads value of Register "r" and displays
	13, 17-19, 24,  value in 3-digit Decimal format.
	25, 30, 32, 34

$SBn    n = speed       $SB1200 selects 1200 bps at serial port.
			$SB2400 selects 2400 bps at serial port.
			$SB4800 selects 4800 bps at serial port.
			$SB9600 selects 9600 bps at serial port.
			$SB19200 selects 19,200 bps at serial port.
			$SB38400 selects 38,400 bps at serial port
			$SB57600 selects 57600 bps at serial port.
		     ***$SB115200 selects 115200 bps at serial port.

&Sn     n = 0, 1 or 2   &S0 forces Data Set Ready On.
		     ***&S1 lets Data Set Ready act normally.
			&S2 Data Set Ready drop is regulated by
			S24 on disconnect.

&SFn    n = 0 or 1   ***&SF0 selects DSR follows CD.
			&SF1 selects DSR independent.

$SPn    n = 0 or 1   ***$SP0 disables UUCP Spoofing
			$SP1 enables UUCP Spoofing

T                       Modem will tone-dial numbers following the T.

&Tn     n = 4 or 5      &T4 means Enable Response to Request for
			Remote Digital Loopback.
		     ***&T5 means Disable Response to Request for
			Remote Digital Loopback.

#Tn     n = 0 or 1      #T0 turns off Trellis Coded Modulation
		     ***#T1 turns on Trellis Coded Modulation

Un      n = 0, 1, 2,    U0 places modem in Analog Loop Originate
	or 3            Test Mode.
			U1 places modem in Analog Loop Answer
			Test Mode.
			U2 places modem in Remote Digital Loopback 
			Test Mode.
			U3 places modem in Local Digital Loopback
			Test Mode.

Vn      n = 0 or 1      V0 means Result Codes sent as digits
			(terse response).
		     ***V1 means Result Codes sent as words
			(verbose response).

W                       Wait for new dial-tone.

&Wn     n = 0 or 1      &W0 causes modem to store its current
			parameters in non-volatile RAM, and
			modem loads these for future sessions
			instead of reading factory ROM defaults, 
			unless &F command used.
		     ***&W1 causes modem to not store parameters.
		     
Xn      n=0 thru 4      X0 selects Basic Result Codes w/o CONNECT 1200, 
			CONNECT 2400)
			X1 selects Extended Result Codes
			(w/ CONNECT 1200, CONNECT 2400)
			X2 selects Standard AT command set with
			NO DIAL TONE
			X3 selects Standard AT command set with
			BUSY
		     ***X4 selects Standard AT command set with
			NO DIAL TONE and BUSY

&Xn     n = o thru 2 ***&X0 Sync internal clocking.
			&X1 Sync external clocking.
			&X2 Sync slave clocking.

#Xn     n = 0 or 1      #X0 causes one XOFF to be sent until buffer                                    
			reaches XON level
			#X1 causes one XOFF to be sent for every        
			character received after modem reaches                                         
			buffer full level

Yn      n = 0 or 1   ***Y0 disables sending or responding to long
			space "break".
			Y1 enables sending or responding to long
			space "breaks".

Z                       All configuration parameters are reset to       
			default values.

,       in Dial         Causes pause during dialing.
	command

;       in Dial         Causes return to Command Mode after
	command         dialing.

!       in Dial         Causes modem to Flash On-Hook.
	command

@       in Dial         Causes modem to wait for ringback, then 5
	command         seconds of silence before processing
			next part of command.

+++AT<CR>               Escape Code. Puts modem in Command Mode while 
			remaining On-Line. Type +++ followed by the letters 
			A and T & up to ten command characters, and hit ENTER.

BREAK AT<CR>            Alternate Escape Sequence. Brings modem into 
			Command mode while remaining On-Line.  Not preceded 
			by AT.  Type BREAK signal, followed by the letters 
			A and T, up to 60 command characters, and hit 
			ENTER.
 
Appendix G
V.25bis Operation

Operation of your modem in ITU-T V.25bis mode provides you with an 
alternate set of commands and responses to those described in the AT 
Command Mode chapter of this manual. The V.25bis mode performs 
dialing functions in the asynchronous or synchronous mode according 
to the recommendations of the ITU-T (Consultative Committee of 
International Telephony and Telegraphy). Synchronous mode, which is 
the more common use of V.25bis, includes both Binary Synchronous 
Communications (BSC) and Synchronous Data Link Control (SDLC).* 
V.25bis is commonly used in IBM (and other) mainframe and mid-
range (S/3x and AS/400) environments. The V.25bis mode commands 
are used to establish data connections over public switched telephone 
networks.

We've already covered the AT command set with its dialing features 
earlier in this manual. The V.25bis commands can be looked at as a 
second command set used  to perform synchronous dialing functions, 
and, since the AT command set cannot perform synchronous dialing, it 
is necessary for dial-up synchronous applications.

V.25bis mode AT commands do not include any modem configuration 
commands. You can execute normal AT commands in V.25bis mode 
for modem configuration.

Delayed and Forbidden Numbers

V.25bis provides the facility to delay failed call retry attempts by 
putting numbers that failed to connect on a special Delayed Number 
list. Subsequent dialing of these numbers are delayed (time specified by 
a country regulation) and an appropriate message displayed. If the 
number is retried more than the maximum allowed number of times 
(number is also specified by country regulation), it is placed on the 
Forbidden Numbers list, and no further retries are allowed. When the 
Forbidden Numbers list is full, no dialing is allowed and a CFIFF 
indication is given. The modem in AT command mode responds with 
NO CARRIER. If country regulations require that the Forbidden 
Numbers list be checked in AT mode, then NO CARRIER is the 
response to a dial attempt in AT mode. Numbers are also be put on the 
Forbidden Numbers list if the Delayed Numbers list is full and a new 
number fails for the first time. In that case, the new number is added to 
the Delayed Number list and the oldest existing number added to the 
Forbidden Numbers list. Numbers are removed from the Forbidden 
Numbers list after a certain time has past (also by country regulation). 
Some country regulations have numbers remain on the Forbidden 
Numbers list permanently. The Delayed Number and Forbidden 
Numbers lists are eight numbers long (20 characters each).

Operation

Operation in V.25bis mode is similar to AT command mode except that 
certain DIP Switch functions are important to its operation. V.25bis 
does not include any speed detection for asynchronous mode, so when 
you are giving commands, you must stay in your initial speed (i.e., if 
you change your terminal speed while entering an AT command, you 
get no responses). In synchronous mode, the modem supplies the clock, 
so the synchronous terminal "knows" the speed.

You must be in V.25bis mode for the commands described here to 
function. Most AT commands also function, except those associated 
with dialing such as ATD, ATN, ATO, and ATU. To get into V.25bis 
mode,  type AT$V1. At this point your modem does no more speed or 
parity detection (things associated with asynchronous operation). To get 
out of V.25bis mode and back into AT command mode, type AT$VO. 
The AT$V2 command allows you to run one V.25bis command from 
AT command mode without leaving AT command mode.

There is no command to select between asynchronous and synchronous 
V.25bis operation. The position of 4-Position DIP-Switch #4 selects 
modes. For synchronous mode, thesynchronous switch must be on, the 
command mode enabled and a jumper plug selects between BSC and 
SDLC.

Another asynchronous mode issue is  connecting at a different speed 
than the speed at which the serial port is set. If your modem port speed 
is different from the serial port speed, you must either:

1.      Enable speed conversion and have flow control on, or
	
2.      Enable connect responses (with the ATX1 command) 
	and change the serial baud rate after receiving a connect message.

DTR dialing is functional in V.25bis mode, except the number dialed is 
from the V.25bis mm memory location 01. Also, if the $VD1 command 
is entered when in Auto-Answer mode, the modem answers 
immediately upon receiving the first ring.

There is no disconnect message (NO CARRIER) if a normal connection 
is made.

Set-Up and Initialization

Before you operate your modem in the V.25bis mode, you need to 
make sure it is set-up properly (various RS232 lines such as DSR and 
CTS act as specified in the V.25bis standard). Set-up involves proper 
DIP-Switch settings, and soft-switches (software controlled conditions).
V.25bis DIP-Switches

	12-Position DIP-Switches
	#1 - Unforced DTR
	#2 - NA
	#3 - NA
	#4 - NA
	#5 - Auto-Answer enabled
	#6 - DSR/CD unforced
	#7 - RTS unforced
	#8 - Command Mode forced
	#9 - NA
	#10 - NA
	#11 - NA
	#12 - NA

	4-Position DIP Switches

	#1 - Unforced CTS
	#2 - Dial-Up
	#3 - Varies per modem model
	#4 - Async/Sync mode set per requirements

	Jumper Plugs

	CTS/RTS - CTS independent of RTS
	DSR - DSR independent of CD
	MI/MIC - NA
	SLDC/BSC - If in Synchronous mode, set per requirements.

V.25bis Mode AT Commands

The following commands either alter standard V.25bis behavior (so you 
must be careful in their use) or they are not allowed, as indicated. All 
other commands can be used in V.25bis operation.

A               Not Allowed
A/              Not Allowed
A:              Not Allowed
D               Not Allowed
D...N           Not Allowed
$D              Alters Operation ($D1 in V25bis is direct 
		call mode)
E               Alters Operation
&F              Alters Operation (removes modem from 
		asynchronous V.25bis mode)
N               Not Allowed
N...N           Not Allowed
O               Not Allowed
P               Not Allowed
T               Not Allowed
U               Not Allowed
W               Not Allowed
X               Alters Operation (X0 no connect message) 
		(X1 connect message)
,               Not Allowed
;               Not Allowed
!               Not Allowed
@               Not Allowed
+++AT<CR>       Not Allowed

V.25bis Responses (Result Codes)

When in V.25bis mode (the AT$V1 command executed), your modem 
provides you with several responses which helps you follow the 
progress of V.25bis operations. These are similar to the Result Codes 
associated with AT Command mode operation. The V.25bis responses 
are in the form of three-character mnemonics as listed on the next page:

INC     Incoming Call (same as RING indicator)

VAL     A valid V.25bis command has been attempted

DLCt    Call delayed for t minutes (number on Delayed list)

CFlrr   Call failure indicator where rr equals:
	et - Engaged tone (same as BUSY)
	nt - Call Answered but No Answer Tone
	ab - Call Not Answered
	fc - Number on Forbidden List
	ns - Number not stored in memory
	ua - User Abort
	nd - No Dialtone
	ff - Forbidden List full
	
LSNmm;dd...dd   Phone number in V.25bis memory
	
LSDmm;dd...dd   Phone number on the Delay list
	
LSFmm;dd...dd   Phone number on the forbidden list
	
CON ssss  Connection at ssss speed (if X1 in effect)

V.25bis AT Commands

The AT commands associated with V.25bis mode are described as 
follows. Note that one command enables and disables V.25bis mode 
and the rest are only operable in the V.25bis mode.

Enable/Disable V.25bis Mode ($V) Command

The function of the $V command is to select the V.25bis mode in 
asynchronous mode. (Synchronous mode is set up with switches. For 
example, the modem could be in AT command mode, (AT$V1), and if 
synchronous mode is enabled with AT Command mode enabled, then  
V.25bis mode is selected). Prior to executing this command, make sure 
that your modem is properly set up to perform the type of operation you 
are performing. Refer to the initialization section of this appendix for 
information about modem set-up. When in V.25bis mode, most normal 
AT commands  also function (except D,N,O and U). V.25bis operates 
in asynchronous or synchronous modes (depending on the position of  
4-Position DIP-Switch #4), and does not check for terminal speed (so 
do not change speeds while in this mode) or parity. In synchronous 
mode, speed is not important since the internal clocks provide 
synchronization.

To place your modem in V.25bis mode from asynchronous mode, enter 
the AT$V1 command. To return to AT command mode, enter the 
AT$V0 command. AT$V2 allows you to run one V.25bis command 
from AT command mode without leaving AT command mode (the 
V.25bis command follows $V2 on the command line).

Clear Number in Memory (CLA) Command

The CLA command clears a specific number in the mm phone number 
memory by entering CLAmm.

Change Serial Baud Rate (CSP) Command

The CSP command  changes the serial baud rate of your modem by 
entering CSPsssss where sssss can equal:
0300    =       300 bps
1200    =       1200 bps
2400    =       2400 bps
4800    =       4800 bps
9600    =       9600 bps
19200   =       19200 bps
38400   =       38400 bps
57600   =       57600 bps
115200  =       115200 bps
			
Dial Phone Number Provided (CRN) Command

The CRN command permits the dialing of the phone number 
immediately following it (from the command line). It is similar to the D 
command of the AT command set, except that the number is first 
checked against the Delayed Number and Forbidden Number list. If 
permitted, depending on the country regulations in effect, the number is 
then dialed. For example, if you type CRN7859875 and hit ENTER, 
your modem  checks the two lists. If the number is on the Delayed 
Numbers list, you can dial that number again after t minutes have 
passed. If the number is on the Forbidden list, a CFIFC message is 
displayed.

You can use various commands from the AT command set within the 
CRN command line to facilitate the dialing process, such as P, T, or W 
for pulse dialing, tone dialing and wait for dial tone. V.25bis supports 
"smart" dialing.

To dial a phone number, type CRNdd...dd where dd...dd is the phone 
number, which can be up to 20 characters long using any character on 
the telephone pad (0 through 9, *, #, P, T, and :).

Some additional dialing characters may be available, based on country 
regulations.

Dial Phone Number Stored in Memory (CRS) Command

A telephone number that you have stored in the modem's memory may 
be automatically dialed after checking it against the Delayed and 
Forbidden number lists by entering CRSmm where mm = 01, 02, 03, 
04,....20. For example, a number stored in mm location 15 is entered 
CRS15 and hitting ENTER, then, if the number in mm memory location 
15 is not on either list, it is automatically dialed.

Store a Phone Number in Memory (PRN) Command

Your modem has a special V.25bis memory for storing phone numbers 
which you may dial by using the CRS command. The memory holds up 
to 20 numbers of 20 characters each. You can store phone numbers in 
this memory with the PRN command. The format for the command is 
PRNmm;dd...dd where mm is the memory location at which you wish to 
store a number (any digits 01 through 20) followed by a semicolon(;) 
and then dd...dd (the number to be stored up to 20 digits long). The 
number can include punctuation as required.

To clear a number from the V.25bis memory, see the CLA command.

Listing Numbers Stored in Memory (RLN) Command

Telephone numbers that you have stored in the modem's V.25bis 
memory may be listed and displayed with the RLN command. It 
displays all twenty mm storage location numbers and associated 
telephone numbers with any command letters and punctuation 
imbedded in each number. The RLN command is similar to the L 
command of the AT command set. To list the V.25bis stored telephone 
numbers, type RLN and hit ENTER.

Listing Delayed Phone Numbers (RLD) Command

When a phone number is dialed either by a CRN or CRS command and 
a connection is not made, the number is entered in the modem's V.25bis 
Delayed Number list along with the number of retry attempts. Any 
further dialing attempts is delayed some amount of time (determined by 
the regulations of each country). While the delay is in progress, the 
modem  gives a DLC indication. The list contains eight numbers. When 
filled, the next number failing "bumps" off the oldest number on the list 
onto the Forbidden Number list. Numbers on the Delayed Number list 
that succeed in a connect attempt are removed. If a certain number of 
failed attempts occur (the number of failed attempts is specified by each 
country), the number is entered into the V.25bis Forbidden Phone 
Number List. Forbidden phone numbers cannot be dialed at all. To list 
the phone numbers on the V.25bis Delayed Phone Number List, type 
RLD and hit ENTER. 

Listing Forbidden Phone Number (RLF) Command

Those phone numbers that have failed to connect the required number 
of times as specified by country regulations are removed from the 
Delayed Number list and entered onto the V.25bis Forbidden Number 
list. Numbers on the Forbidden Number list cannot be dialed at all for 
some maximum amount of time, which is also specified by country 
regulations. In some countries, the time might be one hour, and in 
others the number may never be dialed again. The forbidden list is eight 
numbers long, with the newest number replacing the oldest if the 
memory is full. To list the numbers in the Forbidden list type RLF and 
hit ENTER.

Disregard or Connect to Incoming Calls (DIC or CIC) Command

The Disregard or Connect to Incoming Calls commands are used for 
Auto-Answer operations. Depending on the country regulations, your 
modem waits some amount of time or number of rings before answering 
the call. During that time, you can stop the modem from answering the 
call by entering the DIC (Disregard Incoming Calls) command. The 
CIC (Connect to Incoming Calls) command causes your modem to 
answer the call (either reversing the effect of a DIC command or simply 
have your modem answer the call immediately without waiting the 
regulation time before answering).

DTR Dialing ($D) Command

DTR Dialing is an alternate method of causing the modem to 
automatically dial a number. Data Terminal Ready (DTR) is a signal 
that comes into the modem from the terminal or computer to which it is 
connected via pin 20 of the RS232 interface. In DTR Dialing, the 
modem  dials a stored number as soon as it receives a high DTR signal. 
The DTR Dialing method is popular when using the modem in 
synchronous applications.

To activate DTR Dialing, type the command AT$D1 and hit ENTER. 
The modem now dials the phone number stored as N0 when it receives 
a high DTR signal (see the D...N command in Chapter 4). DTR must 
remain high for the duration of the call, until disconnect. To deactivate 
DTR Dialing, type the command AT$D0 (or AT$D) and hit ENTER.
When you use DTR Dialing, be sure that  DIP-Switch #1 is in the UP 
position, so that DTR is not forced on.

In addition, when using DTR Dialing in a synchronous application, be 
sure that DIP-Switch #8 is in the UP position to disable V.25bis 
Command Mode.

ITU-T V.25bis Country Specific Information

Due to the flexibility of the V.25bis standard, each country may 
establish specific regulations governing the way operations are handled. 
The purpose of this document is to detail each country's specific 
regulations that affect operation of V.25bis in Multi-Tech modems.

1.  Italy
a)      Command/Indication modifications
	1.      Phone number indications include status; 
		ZPSTTT
		a)      Z - U, D, or F, for Unrestricted, 
			Delayed or Forbidden
		b)      P - Delay time if delayed
		c)      S - Number of retries so far
		d)      TTT - Interdiction time to further 
			attempts
	2.      Modify RLN command to allow memory 
		location parameter
		a)      RLNmm is now valid to list one 
			number in memory
	3.      PRN and CLA commands do not work on 
		active memory locations
		a)      Active number are ones who are on 
			the delay or forbidden lists
	4.      Added dialing digit '<' to indicate 2 second 
		pause
b)      Delayed and Forbidden list behavior
	1.      5 retries without delay
	2.      2 minute delay between next 4 retries
	3.      After 9 retries the number is put on the 
		forbidden list
	4.      120 minute timer is started on entry to delay 
		list
	5.      When it runs out, the number is removed 
		from whichever list it is on
c)      Auto-Answer mode behavior
	1.      Auto-Answer in 5 seconds if no DIC
	2.      Get 10 seconds after DIC to enter CIC
	3.      If 10 seconds times out then no connection is 
		possible

2. Switzerland
a)      Command/Indication modification
	1.      Modem must remain on-hook for 5 seconds 
		after disconnect
	2.      Modem must remain on-hook for 5 minutes 
		after 4 consecutive failed calls
	3.      If modem must remain on-hook, then it is 
		"paused"
	4.      If the modem is paused and a call is 
		attempted a PAU indication is given.
		a)      PAUt Modem is paused for t 
			minutes
b)      Delayed and Forbidden list behavior
	1.      2 minute delay between 4 retries
	2.      After 4 retries the number is put on the 
		forbidden list
	3.      The number remains on the forbidden list 
		forever
c)      Auto-Answer behavior
	1.      Auto-Answer mode after 2 rings if no DIC

3.      Austria
a)      Command/Indication modification (none)
b)      Delayed and Forbidden list behavior
	1.      No delay between retries
	2.      After 2 retries to numbers that answer, but 
		give no answer tone (CFINT), the number is put on the 
		forbidden list
	3.      After 10 retries with busy or no dialtone, the 
		number is put on the forbidden list
	4.      The number remains on the forbidden list 
		forever
	5.      Delayed and Forbidden Numbers lists are 
		checked when dialing in AT mode. 
If dialing is not possible then NO CARRIER is the response.
c)      Auto-Answer behavior
	1.      Auto-Answer in 5 seconds if no DIC

4. France
a)      Command/Indication modification (none)
b)      Delay and Forbidden list behavior
	1.      2 min. delay after 1st call, 4 after 2nd, 6 
		after 3rd, etc.
	2.      After 5 retries, the number is put on the 
		forbidden list
	3.      The number remains on the forbidden list 
		forever
	4.      Delayed and Forbidden Numbers lists are 
		checked when dialing in AT command mode. If dialing is not possible 
		then No Carrier is the response.
c)       Auto-Answer mode behavior
	1.      Auto-Answer in 5 seconds if no DIC

5. Belgium
a)      Command/Indication modification (none)
b)      Delay and Forbidden list behavior
	1.      1 min. delay between calls
	2.      After 4 retries, the number is put on the 
		forbidden list
	3.      The number remains on the forbidden list for 
		1 hour after entry to forbidden list
	4.      Delayed and Forbidden Numbers lists are 
		checked when dialing in AT command mode. If dialing is 
		not possible then No Carrier is the response.
c)      Auto-Answer behavior
	1.      Auto-Answer in 5 seconds if no DIC.

6. Singapore
a)      Command/indication modifications
	1.      Dialing digit '=' means wait for dialtone (acts 
		the same as ':' in dialing string).
b)      Delay and Forbidden list behavior
	1.      5 retries without delay
	2.      2 minute delay between next 4 retries
	3.      After 9 retries the number is put on the 
		forbidden list
	4.      120 minute timer is started on entry to delay 
		list
	5.      When it runs out, the number is removed from 
		whichever list it is on.


Appendix H
RS232C Interface Specifications

The MT2834MR's RS232C interface circuits have been designed to 
meet the electrical specifications given in EIA (Electronic Industries 
Association) RS232C standards. All signals generated by the modem 
are approximately 10 volts when measured across a load of 3000 ohms 
or greater. The receiving circuits of the modem  accepts signals in the 3 
to 25 volt range. The voltage thresholds are:
	
Negative = voltage more negative than 3 volts with respect to 
signal ground
	
Positive = voltage more positive than +3 volts with respect to 
signal ground

SIGNAL INFORMATION:             NEGATIVE        POSITIVE 
Binary State                    One             Zero            
Signal Condition                Mark            Space           
Control and Timing Function     Off             On

The input impedances of all modem circuits which accept signals from 
the data processing terminal or CPU equipment have DC resistances of 
4.7K. For more specific details, consult the EIA RS232C standard 
itself.

The following chart lists the EIA RS232C interface pins and circuits 
present on the MT2834MR's RS232C Interface connector. All other 
pins are unused.

Pin     Multi-Tech      EIA     Signal  Circuit 
Assign. Designation     Circuit Source* Function
1       PG              _       _       Protective Ground
2       SD              BA      DTE     Transmitted Data
3       RD              BB      DCE     Received Data
4       RTS             CA      DTE     Request to Send
5       CTS             CB      DCE     Clear to Send
6       DSR             CC      DCE     Data Set Ready
7       SG              AB      _       Signal Ground
8       CD              CF      DCE     Data Carrier Detector
9       +V              +V      DCE     Test Voltage
12      HS              --      DCE     High Speed
15      TC              DB      DCE     Transmit Clock
17      RC              DD      DCE     Receive Clock
20      TR              CD      DTE     Data Terminal Ready
22      RI              CE      DCE     Ring Indicator
24      XTC             DA      DTE     External Transmit Clock
25      OOS             CN      DTE     Terminal Busy

*       DTE = Data Terminal Equipment (terminal or computer)    
	DCE = Data Communications Equipment (the modem)

The computer or terminal should be supplied with a cable terminated 
with a Cinch DB25P (or equivalent) connector mounted in a Cinch 
DB51226-1 (or equivalent) hood assembly as specified by the EIA 
RS232C standard.

FUNCTIONAL DESCRIPTION OF MT2834MR RS232C SIGNALS:
Transmitted Data - Pin 2, SD (BA)
Direction: to modem

Signals on this circuit are generated by the customer's terminal and 
transferred to the transmitter of the MT2834MR. A positive signal is a 
space (binary 0) and a negative signal is a mark (binary 0). The 
transmitting terminal should hold this line in the marking state when no 
data is being transmitted, including intervals between characters or 
words. The TRANSMIT (SD) LED indicates the status of this circuit.

Received Data - Pin 3, RD (BB)
Direction: from modem

The lead is the data output of the modem. Data signals received from 
the remote modem are presented on this line. When no carrier signal is  
received (pin 8 negative), this line is forced into a marking condition. 
The RECEIVE (RD) LED indicates the status of this signal.       

Request To Send - Pin 4, RTS (CA)
Direction: to modem

The RTS signal indicates to the modem that the computer or terminal 
has data to transmit.

Clear To Send - Pin 5, CTS (CB)
Direction: from modem

The CTS line indicates to the terminal that the MT2834MR will 
transmit any data present on the Transmit Data line (pin 2). 

Data Set Ready - Pin 6, DSR (CC) 
Direction: from modem

DSR ON, indicates that the MT2834MR is in the data mode and is 
connected to the communications channel. This signal is on during 
analog-loop-test mode.

Signal Ground - Pin 7, SG (AB)

The SG lead is connected to signal ground of the modem. It establishes 
the common ground reference for all other interface signals.

Data Carrier Detect - Pin 8, CD (CF) 
Direction: from modem

DCD On (positive voltage) indicates that data carrier has been received 
from the other modem. This circuit does not typically turn on in the 
presence of message circuit noise or out-of-band signals. There is a one 
second delay between when the carrier tone is detected and when the 
CD circuit is turned on.

This signal goes off if received data carrier falls below the receiver 
threshold for more than 37 mSec. When CD is off, the Received Data 
circuit (pin 3) is held to the marking state.

Test Voltage - Pin 9, XV
Direction: from modem

The XV lead has 330 ohms of resistance to +12 volts DC. This lead 
may be used to strap other signals high. For example, if the terminal 
does not supply a DTR (Data Terminal Ready) signal, Pin 9 may be 
jumpered to Pin 20 (DTR) on the RS232 connector or in the cable to 
force DTR on.

High Speed - Pin 12, HS

The On condition of this circuit indicates that the modem is in the high 
speed (1200 bps) mode.  This circuit is commonly used to signal the 
computer or terminal to which the modem is connected to switch to its 
1200 bps setting.

Transmit Clock - Pin 15, TC (DB)
Direction: from modem

The TC  signal is provided only when the MT2834MR is used in the 
synchronous mode. The clock is a square wave and is used to provide 
the computer or terminal with timing information for its Transmit Data 
circuit (pin 2). This clock is provided on the interface at all times when 
the modem is in synchronous mode. 

The first signal element of the Transmitted Data signal should be 
presented by the terminal on the first positive (Off to On) transition of 
TC which occurs after the CTS circuit on pin 5 is turned on. The 
transmitted data is sampled by the modem on negative transition of TC. 

Receive Clock - Pin 17, RC (DD)
Direction: from modem

The RC signal has the same characteristic of Transmit Clock, with the 
exception that it is used to provide the computer or terminal with timing 
information for its Receive Data (pin 3) circuit. The negative transition 
(On to Off) of RC indicates the center of each signal element on the 
Received Data circuit.

Data Terminal Ready - Pin 20, TR or DTR (CD)
Direction: to modem

This signal (TR or DTR) provides a means for the terminal or computer 
to control the modem's connection to the communications channel. A 
high DTR signal is required by the modem to be able to communicate. 
Turning DTR off for more than 50 mSec forces the modem to 
disconnect.

The most common use of DTR is in automatic answer applications. A 
high DTR signal is required by the modem to answer a call. A 
frequently used method is to have the computer turn on DTR in 
response to RI (Ring Indicator), which allows the modem to answer. 
Later, DTR is turned off at the conclusion of the log off procedure, 
which forces the modem to disconnect, enabling it to receive another 
call. In non-auto answer applications it is advisable to leave DTR on 
using the modem's DIP-Switch option. This is the standard factory 
setting. An alternative is to provide a constant high DTR from the 
terminal or computer. The Data Terminal Ready (DTR) LED indicates 
the status of this signal. 

Ring Indicator - Pin 22, RI (CE)
Direction: from modem

This signal remains on for the duration of the ringing signal. When a 
ring signal is received by the modem, the modem automatically answers 
after the first ring. The modem  can answer after a specified number of 
rings which can be programmed in AT Command Mode, but if none is 
specified, the modem answers after the first ring.

External Transmit Clock - Pin 24, XTC
Direction: to modem

Supplies the same function as transmit clock on Pin 15.

Terminal Busy (Out of Service) - Pin 25, OOS 
Direction: to modem

The Terminal Busy (OOS) circuit is not defined in the RS232C 
standard, but is used by us and most manufacturers to make the phone 
lines busy to incoming phone calls. Pin 25 is not typically connected to 
the RS232C interface when shipped from the factory; it can be ordered 
connected as an option. If pin 25 is connected and is brought high, the 
modem is placed Off Hook, and is busy to incoming calls.

Appendix J
Multi-Tech Systems Escape Methods

Introduction

You may find it necessary sometimes to issue AT commands to your 
modem while you are on-line with a remote modem, without 
disconnecting the call.  If so, you will want to take advantage of Escape 
methods which allow you to change the modem's mode of operation 
from On-Line mode to Command mode, where you may issue AT 
commands, without disconnecting.  While you may then return on-line, 
typically most users escape so that they may hang up a modem upon 
completion of a call.

Our modems offer two Escape Methods:  in-band, and out-of-band.  
Both incorporate Time Independent Escape Sequence (TIES) 
methodology.  An escape sequence is a pattern, or sequence, that the 
modem recognizes as its signal to shift from On-Line mode to 
Command mode.  Time Independent means that the modem recognizes 
the escape sequence without a prefixed and/or suffixed delay.

In an in-band escape, the modem recognizes the escape sequence as a 
pattern sent to it as part of the data stream or band (hence its name).
In an out-of-band escape, the escape sequence is a pattern that cannot 
and does not occur in the data stream.

Our in-band escape method is:  +++AT<CR>.
Our out-of-band escape method is:  <BREAK>AT<CR>.

A BREAK signal cannot be sent as part of a data file; instead it is sent 
by a direct program command to the UART used by that computer.
BREAK is defined as either the transmission of binary 0 for a minimum 
of 10 bits; or as a minimum interval of 135 milliseconds as established 
in the ITU-T X.28 standard.  There are routines in high level languages, 
and keys on most computers that have been established to send BREAK 
for fixed intervals, but you may control the BREAK's duration by 
refering to your UART's specifications.

How to Select an Escape Method

If you want your modem to escape and then wait for you to issue a 
command before it will return to On-Line mode, then use +++AT<CR>.  
You might use this method if you find you need to review a help screen 
in the middle of a communications session.

If you wish to combine the escape with a command (or commands) and 
with an immediate return to On-Line mode, then use the 
<BREAK>AT<CR> method.  You may also use this method to have 
the modem wait before it will return On-Line.

You may select your modem's escape method by using an AT%E 
command.

The AT commands used to select the modem's Escape Method are:

%E0 = Escape Disabled                    
%E1 = +++AT method (default)             
%E2 = <BREAK>AT method           
%E3 = Both escape methods enabled
%E4 = Disable OK response to +++
%E5 = Enable OK response to +++

Escape Method 1:  +++AT<CR>

In the following example, a user who is On-Line decides to set S0 
Register to 1, to configure the modem to answer on the first ring.

1.      The user enters the sequence +++AT<CR> .  The sequence  
	is sent to the modem.

2.      The modem transmits the +++.

3.      The modem buffers AT and starts the Wait for <CR> timer.

4.      Upon receiving the <CR> the modem escapes to Command    
	mode.

5.      The modem responds OK.

6.      The user enters the command ATS0=1<CR>.  This           
	sequence is sent to the modem.

7.      The modem buffers ATS0=1<CR> and identifies it as a     
	valid command.

8.      The modem executes the command, setting S0=1.

9.      ATO<CR> is sent to the modem.

10.     The modem returns to On-Line mode.

Escape Method 2:  <BREAK>AT<CR>

In the following example, a user who is On-Line decides to set S-
Registers S0 to 1, to configure the modem to answer on the first ring.

1.      The <BREAK> signal is sent to the modem.

2.      The modem buffers <BREAK>.

3.      The modem starts the S32 Wait for <CR> timer.

4.      ATS0=1<CR> is sent to the modem.

5.      The modem buffers ATS0=1<CR> and identifies it as a valid       
	command.

6.      The modem escapes to Command mode.

7.      The modem executes the command, setting S0=1.

8.      The modem returns to On-Line mode.

S-Registers and Escape Sequences

There are two S-Registers that you may set to modify the functioning of 
your escape sequences.  The first is S-Register S32, which establishes a 
value for how much time may elapse between the receipt of the 
beginning of the escape sequence, whether <BREAK>AT, or +++AT, 
and the receipt of a <CR>.  This interval is known as Wait for <CR> 
Time, or BREAK passthru.

You may assign a value to S32 in increments of 100 milliseconds.  The 
default value is 20, or 2 seconds.

In the +++AT<CR> method, the Wait for <CR> Time interval begins 
once the A in +++AT is received by the modem.

In the <BREAK>AT method, the Wait for <CR> Time interval begins 
once the modem has received the BREAK signal.

You may use S-Register S34 in conjunction with our in-band escape 
sequence, +++AT<CR>, to establish the maximum number of 
characters that your modem can buffer following an "AT," before a 
<CR> must be received.  The default value is 10 characters.  Do not 
confuse this buffer size with our regular Command mode buffer length 
of 60 characters.

S-Register S34 does not affect our out-of-band escape sequence's buffer 
length, which is fixed at 60 characters.

Aborting an Escape Sequence

The +++AT<CR> escape will abort if you do not issue a <CR> before 
the Wait for <CR> Time interval expires.

The <BREAK>AT<CR> method will also abort if you do not issue a 
<CR> before the Wait for <CR> Time interval expires, and also if any 
of the following occurs:

1.      An illegal sequence is detected, including:
	a)  A character other than A follows the <BREAK>;
	b)  A character other than T follows <BREAK>A;
	c)  Two BREAKS are received in succession;

2.      The command buffer overflows before a <CR> occurs.
If you have any questions about the information contained in this 
document, please direct them to:

Technical Support

c/o Multi-Tech Systems, Inc.
2205 Woodale Drive
Mounds View, Minnesota  55112 USA


Appendix K
Remote Configuration

Introduction

This chapter describes how the MT2834MR Remote Configuration 
feature operates. This feature uses a multilevel security system that 
involves the use of LOGIN passwords, SETUP passwords, and remote 
escape characters.

The primary level security code is the modem's LOGIN password. Once 
this password is entered, other passwords can be used. For instance, 
entering the LOGIN password lets you enter the SETUP password.
The remote escape character is the key to using the Remote 
Configuration feature. The remote escape character lets you enter 
Command mode via a remote call, so that you can type AT commands 
just as if you were locally connected. You must also type your modem's 
SETUP password. The remote escape character is contained in S-
Register S13.

Remote Configuration Description

The Remote Configuration feature is a network management tool that 
lets you configure modems remotely. This means you can configure 
modems anywhere in your network from one location, without having 
to visit the sites or rely on remote users to follow your instructions. 
With Remote Configuration, which is protected by two-level security, 
you can downline load new parameters, program new V.42 capabilities, 
and implement new features. Remote Configuration also makes 
troubleshooting remote locations a lot easier.

S-Register S13 contains the special remote configuration escape code. 
When calling a Remote Configuration equipped modem, you enter the 
proper remote escape code and SETUP password. After entering both 
correctly, you can then execute AT commands as if you were connected 
locally. If you set S-Register S13 to zero, Remote Configuration is 
disabled.

Initial SETUP Procedures for Remote Configuration

Your modem is shipped with default LOGIN and SETUP passwords 
(LOGIN=MULTI-TECH and SETUP=MODEMSETUP) so you can 
configure the modem. Because the defaults are in the owner's manual, 
anyone can find out what they are. You should change the codes as the 
first step of your initialization procedure.

To change your modem's LOGIN and SETUP passwords, follow the 
steps below.

NOTE:   Passwords are upper/lower case sensitive. The case you  
	enter here is the case that must be used at login.

Modem LOGIN, SETUP, and Remote Escape Codes

1.      Type AT#IMULTI-TECH and press ENTER. Your 
	modem responds with: OK (if the LOGIN password is wrong, the 
	modem's response is ERROR)
	
2.      Type AT#SMODEMSETUP and press ENTER. 
	Your modem responds with the following: OK (or ERROR if the wrong 
	SETUP password is entered)

NOTE:   At this point you can change the LOGIN password
	and SETUP passwords.
	
3.      Type AT#I=xxxxxxxxxx (with any keyboard 
	characters used: minimum = 6, maximum = 10) and press ENTER. 
	Your modem responds with: OK
	
4.      Type AT#S=yyyyyyyyyy (with keyboard characters 
	used: minimum = 6, maximum = 10) and press ENTER. Your modem 
	responds with: OK

To change the status of your Remote Configuration feature:
	
5.      To disable Remote Configuration, set S-Register S13 
	to 0 (zero). See Chapter 6 for details on how to set S-Register values.
	
6.      To enable Remote Configuration and change the 
	remote escape character, type in a new S-Register S13 value. 
	
Remote Configuration AT Commands 

The following AT commands are used with the Remote Configuration 
feature.

#I      Modem LOGIN Password

The #I command lets you select a unique LOGIN password for your 
modem. Once you have selected a LOGIN password for your modem, it 
only responds to that code. Your modem is shipped with MULTI-
TECH as its default password so that you can gain access to the 
command initially.

#S      Modem SETUP Password

The #S command lets you select a unique SETUP password for your 
modem. Once you have selected a SETUP password for your modem, it 
only responds to that code. Your modem is shipped with 
MODEMSETUP as its default password, so that you can gain access to 
the command initially.

Remote Configuration S-Register

S-Register S13 is used with Remote Configuration. It defines the 
MT2834MR remote configuration escape character. When the S13 
character is entered three consecutive times from a remotely connected 
site, your modem responds to it with its Remote Configuration 
procedure. The default remote configuration escape character is the 
"%" sign. See Chapter 4 for more information about this S-Register.

Remote Configuration Procedures

This section explains how to use the Remote Configuration feature; 
they are the same whether or not a call originates from the remote 
modem. 

Remote Configuration Operation

1.      Enter a break signal, then type the S13 remote 
configuation escape character three times (the default S13 value is the 
"%" sign).  The modem responds with:
	1. - DATA Mode
	2. - COMMAND Mode

2.      Select 1 or 2. With option 1, the modem goes back 
	into Data mode and with option 2, the modem responds with 
	Password>.

3.      Type your SETUP password and, if the code is 
	correct, the modem responds with OK.
	
	You can now use any AT commands remotely as if 
	they were entered locally. You cannot change the LOGIN password 
	until you enter the proper LOGIN password. 
	
4.      When you are done typing AT commands and you 
	wish to exit, type AT0 and press ENTER. The modem responds with:
	1. DATA Mode
	2. COMMAND Mode
	
5.      Type 1 to go back on-line with your computer, or 
	type 2 and the correct password to talk to your modem.
