GDI SM2400 User Manual

MODEL SM2400

2400 BAUD

DIAL-UP MODEM

SMART MODEM

USER GUIDE

280 Interstate 80 West Exit 1 / PO Box 1330, Verdi NV 89439

Phone: [phone] Fax: [phone] E-mail: [e-mail]

PROPRIETARY DATA

This document contains confidential, proprietary data with all rights

and titles reserved by GDI Communications LLC. By accepting

this document, the recipient assumes custody hereof and agrees not

to disclose this data or any portion of this data to any unauthorized

person without the prior written consent of GDI Communications

LLC. Recipient further agrees not to incorporate these drawings,

specifications or technical information, in whole or in part, in any

other product or endeavor.

THIS LEGEND SHALL BE INCLUDED ON

ANY REPRODUCTION OF THIS DOCUMENT

GDI Communications LLC

MODEL SM2400

Smart Modem

Revision B-2.0

USERS MANUAL

GENERAL

The GDI Model SM2400 is a Hayes compatible Dial-up modem, designed for plug-in
compatibility with 170 series Traffic Controllers. It is intended to allow, with proper
software support, communication between a 170 and a host computer over standard dial­up or leased telephone lines. The GDI Model SM2400 includes a modulator, demodulator,
filters, phone line interface, and 170 controller interface. It offers 300/1200/2400 baud
transmission & reception, auto-dial/-answer/-speed detect, and Hayes command set
compatibility, all on a single board with the standard Model 400 form factor.
In addition to all of the features normally found in a Hayes-compatible modem, the GDI
Model SM2400 is fully temperature tested.

FEATURES

- Form factor consistent with the standard Model 400.

- Front edge mounted status indicators.

- Industry standard 'AT' command set.

- Auto-Dial Auto-Answer Auto-speed detect.

- Highly flexible configuration options.

- Fully temperature tested.

- Configuration options stored in NVRAM - no jumpers.

- Call progress monitor speaker.

- May be cable connected to auxiliary ACIA

TABLE OF CONTENTS

PAGE
GENERAL CHARACTERISTICS ………………………………………………… 3
INSTALLATION ……………………………………………………………………6
SHIPPING CONFIGURATION…………………………………………………… 7
ADJUSTMENTS…………………………………………………………………… 7
THEORY OF OPERATION ……………………………………………………… 8

System Description ………………………………………………………… 8
Description of Circuit Operation…………………………………………… 9

MAINTENANCE………………………………………………………………… 10

Preventive Maintenance…………………………………………………... 10
Alignments………………………………………………………………… 10
Trouble Analysis…………………………………………………………... 10
Special Considerations…………………………………………………….. 10

Waveforms and Voltage Measurements…………………………………… 10
TEST PROCEDURE………………………………………………………………. 11
COMMAND SET…………………………………………………………………. 12
CONFIGURATION (S) REGISTERS……………………………………………. 24
PROGRAMMABLE OPTIONS NOT SAVED IN NVRAM……………………. 30
PROGRAMMABLE OPTIONS SAVED IN NVRAM………………………….. 30
COMMAND SUMMARY………………………………………………………... 31

General Characteristics

INDICATORS TXD Transmitted Data

RXD Received Data
OH Off Hook, on when modem is off hook
DTR Terminal Ready, on when host is ready
HS High Speed, on when in 2400 baud mode
DCD Carrier Detected
AA Originate/Answer mode, on when in answer mode

OPERATING TEMPERATURE RANGE

-30°C to +70°C

HUMIDITY
95% Relative Humidity, non-condensing

LINE REQUIREMENTS
(a) Public switched telephone network
(b) Private unconditioned leased lines

MODES OF OPERATION
Asynchronous
Full or half duplex
Automatic and manual call originate Automatic and manual call answer

COMPATIBILITY
CCITT V.22 bis, V.22 A&B, V.21, Bell 212A and Bell 103 Automatically adapts to
calling or called modem

ASYNCHRONOUS DATA RATES
2400 and 1200 bps, character asynchronous 0 - 300 bps asynchronous

ASYNCHRONOUS CHARACTER FORMAT
Character length of 8, 9, 10 or 11 bits Parity - odd, even, mark, space or none

ASYNCHRONOUS OVERSPEED/UNDERSPEED RANGE
Nominal rate -2.5% to +1.25% in character asynchronous mode Data formatter follows
CCITT V.22 bis and Bell 212A

TELEPHONE LINE INTERFACE
Meets FCC part 68 requirements
Maximum transmit level -9dBm (600 fl) Two wire full duplex. Uses TIP and RING

MODULATION
V.22 bis - 16 Level Quadrature Amplitude Modulation (QAM)
V.22 and 212A - 4 Level Differential Phase Shift Keying (DPSK)
V.21 and 103 - Phase-Coherent Frequecy Shift Keying (FSK)

TRANSMIT CARRIER FREQUENCIES
V.22 bis:
V.22:
212A: ORIGINATE 1200 Hz +/- 0.01%
ANSWER 2400 Hz +/- 0.01%

V.21 @ 300 bps:
ORIGINATE ‘ space’ 1180 Hz +/- 0.01%
ORIGINATE ‘ mark’ 980 Hz +/- 0.01%
ANSWER ‘ space’ 1850 Hz +/- 0.01%
ANSWER ‘ mark’ 1650 Hz +/- 0.01%

Bell 103:
ORIGINATE ‘ space’ 1070 Hz +/- 0.01%
ORIGINATE ‘ mark’ 1270 Hz +/- 0.01%
ANSWER ‘ space’ 2020 Hz +/- 0.01%
ANSWER ‘ mark’ 2225 Hz +/- 0.01%

LINE EQUALIZATION
(a) Fixed compromise equalization in transmitter
(b) Adaptive equalizer for 1200 and 2400 bps in receiver

INTERFACE SIGNALS
RS232C levels with CCITT V.24 protocols

AUTODIALER TYPE
DTMF or pulse type dialing, specified in commands

DTMF TONE PAIR BALANCE
Better than 3dB

DTMF TONE DURATION AND SPACING
Variable from 50 to 255 milliseconds (Register S11)
Default duration 100 milliseconds

PULSE DIALING RATE
10 pulses per second

PULSE DIALING DUTY CYCLE
39/61% (US) or 33/67% (UK Hong Kong) make/break ratio

PULSE DIALING INTERDIGIT INTERVAL
650 milliseconds

BILLING DELAY INTERVAL
2 seconds silent time, before answer tone

GUARD TONES
Guard tones of 1800 Hz or 550 Hz may is transmitted by the answering modem, for echo
suppression. Default - no guard tone. Guard tone will not be transmitted in Bell 212A or
103 modes.

COMMAND BUFFER SIZE
40 Characters maximum, which includes the required carriage return. The modem does
not count the required AT prefix.

FAILED CALL TIMER
2-255 seconds (Defaults to 30 seconds)

RESULT CODES (TO TERMINAL OR 170)
Ability to limit, abbreviate, or suppress codes

RECEIVE CARRIER DETECT
Off-to-On Threshold: -43 dBm On-to-Off Threshold: -48 dBm
Hysteresis: Greater than 2 dB

TIMING
Request to send-Clear to send Delay
As per CCITT and BELL protocols during modem handshaking.
Delay specified by register S26. (default 10 mS)

TIMING
DCD ON delay
As per CCITT and BELL protocols (600 mS)

TIMING
DCD OFF delay

52.5 +/- 12.5 mS at 2400,1200 bps
17 +/- 7 mS at 300 bps

PERFORMANCE
Bit Error Rate of 1 bit per 100,000 for a S/Noise Ratio of 10dB
TxD Level -10 dBm
RxD Level -45 dBm

POWER
+12 Volts +/- 5% at 200 mA

-12 Volts +/- 5% at 200 mA

170 CONTROLLER INTERFACE
ETA RS-232-C via standard 400 modem edge connector pinout or a 9 pin Male D-Sub
connector J14, user selectable.

J14 PINOUT (9 PIN MALE RS232)
Pin Function Direction
1 DCD (Data Carrier Detected) Output
2 RXD (Received Data) Output
3 TXD (Transmitted Data) Input
4 DTR (Data Terminal Ready) Input
5 GND (Signal Ground) Common
6 DSR (Data Set Ready) Output
7 RTS (Request To Send) Input
8 CTS (Clear To Send) Output

170 EDGE CONNECTOR PINOUT

Pin Function
A & B Signal Common (DC Ground)
C & D +12 Volts
E & F -12 Volts
K DCD (Data Carrier Detected)
L RTS (Request To Send)
M TXD (Transmitted Data)
N CTS (Clear To Send)
P RXD (Received Data)

TELCO CONNECTOR PINOUT (LINE)
Pin Function Direction
4 TIP TERMINAL To/From RJ11C jack
3 RING TERMINAL To/From RJ11C jack

INSTALLATION
Before installing the Model SM2400, it is necessary to determine if the controller
application software expects to talk to the Smart Modem via ACIA1 (modem slot and C2)
or ACIA2 (C20 only). If the software communicates with the smart modem via ACIA1,
installation consists of simply plugging the modem into the modem slot and connecting
the phone line to the modular jack (LINE). If the softwar talks to the Smart Modem
through ACIA2 (C20), it is necessary to remove the jumper arrangement plugged into J3
(Edge Connector Enable) and supply a cable between C20 and the 9 pin connector of the
modem (J14). One can then plug in the modem and connect the phone line.

If you have completed the steps in the above paragraph and are still experiencing
problems you are encouraged to contact your software supplier and/or GDI. The Model
SM2400 is shipped from the factory in the most commonly used operating configuration
but some software suppliers require different operating options that can be accommodated
by reconfiguring non-volatile RAM.

ADJUSTMENTS

NVRAM
The Model SM2400 is equipped with Non Volatile Random Access Memory. This
memory stores modem operating parameters even when power is off. Two complete User
Profiles and four Dialing Strings may be stored. This eliminates the need for jumper
arrangements while allowing more flexibility. A detailed description of which parameters
are stored in this memory and how to alter its contents is given in the Command Set
section.

Switches
The GDI Model SM2400 has an eight position DIP switch (SW1) that is used to 'strap'
operating parameters. Only positions 1 through 6 are used. The following is a description
of their function.

Switches 1 through 4 - TXn
These switch positions are used to adjust transmit levels. They are preset at the factory
and should NOT be change
user as doing so may cause a violation of FCC regulations and/or compromise
performance. If these switches are inadvertently altered, restore them to: switch 1 ON,
Switches 2,3,4 OFF

Switch 5 - BELL/CCITT
This switch position has been superseded by an enhanced "B" command. It should be left
in the "OFF" condition.

Switch 6 - Dumb/Smart
If switch 6 is OFF the modem will ignore commands and refrain from sending result
codes to the terminal (Dumb mode). To use the dumb mode, first store operating
parameters in NVRAM, then turn switch 6 OFF. At the next power up the modem will
assume the dumb mode. Turn switch 6 ON and power up to reestablish Smart mode.
(factory default ON)

SHIPPING CONFIGURATION

The modem is shipped from GDI in a slightly different configuration than described in the
command &F. This is for compatibility with most 'traffic' software. The differences are:
1200 baud instead of 2400 baud communication rate, and Auto-Answer enabled.

To restore the modem to shipping configuration:

1. Connect to 1200 baud terminal, power off, back on.

2. AT&F <return> fetch factory profile

3. AT&C0&D1 <return> DCD and DTR options

3. ATS0=1 <return> Auto-Answer enabled (first ring)

4. AT&W0 <return> Write current profile to NVRAM

THEORY OF OPERATION

System Description

The Model SM2400 modem is designed to provide the Traffic Industry with the
advantages of a Hayes compatible Dial-up modem, while minimizing limitations imposed
by connecting it to a 170's 6850 Asynchronous Communications Interface Adapter
(ACIA). The 6850 RS-232-C control lines are not sufficient in number to provide
complete control over an off-the-shelf Hayes modem. The 170 communication signal
lines, available at the C2S and/or C2OS connectors, consist of the following:

RS-232 170

NAME DESIGNATION DESIGNATION ORIGIN FUNCTION
TXD BA PIN K (DI) 170 Digital data input
RXD BB PIN L (DO) Modem Digital data output

from modem

CTS CB PIN M (CTS) Modem Flags the 170 that the

modem is ready to
transmit data

RTS CA PIN J (RTS) 170 Signals the modem that

the 170 wants to
transmit

DCD CF PIN H (CD) Modem Flags the 170 that a

carrier signal is being
received

GND AB PIN N (GND) Both Circuit common

An off-the-shelf Hayes modem minimally requires the following additional signal lines to
implement full operation, for which support from a 170 ACIA is not available:

NAME DESIGNATION ORIGIN FUNCTION
DSR CC Modem Indicates that the modem is ready to

transfer data.

DTR CD Host Indicates to modem that host is ready

to communicate.

The Model SM2400 solves this problem by essentially ignoring DTR (See Configuration
Command &D). The factory default for DSR is always on (See &S). Since DSR is not
monitored by the 170, this only becomes an issue when the Model SM2400 is connected
to Data Terminal Equipment.
From a system perspective, the modem has basically three interfaces With the outside
world.

1. Power Supply Edge Connector P1

2. RS-232 Edge Connector P1 or DB-9 J14

3. Phone Line RJ11-C Connector "LINE"

DETAILED CIRCUIT DESCRIPTION

The GDI Model SM2400 consists of 6 basic functional blocks (figure 2). They are the
power supply section, the DAA (Data Access Arrangement), analog front end, application
specific processor, NVRAM, and the RS-232 interface section. The following discussion
describes their operation.

Power Supply
The power supply section is where all voltages necessary for operation of the modem are
derived. The voltages required on the Model SM2400 board are +12, -12, +5, & -5 volts.
The +/- 12 volts is obtained via the edge connector of the Model SM2400. VR1 regulates
the +12 volts to produce a regulated +5 volts. VR2 regulates the -12 volts to produce a
regulated -5 volts.

DAA
This is the telephone line interface. Its functions are:

1. Comply to impedance and isolation requirements.(FCC part 68)

2. Furnish a method of switching between the modem and an optional telephone handset.

3. Provide for on/off hook control as well as pulse dialing.

4. Ring detection.
The FCC has stringent rules regarding the characteristics of devices connected to public
telephone networks. These are detailed in Part 68 of the Code of Federal Regulations.
Transformer Tl presents the proper impedances to the telephone line while isolating the
TIP and RING signals from the analog front end. Opto-coupler U10 is the isolating
element of the ring detector subsection of the DAA. Relay K2 allows isolated switching of
the phone line between the modem and an optional handset under modem control. Relay
Ki allows isolated on/off hook control and a mechanism for pulse dialing.

Analog Front End
The purpose of the analog front end is to:

1. Perform complex receive and transmit filter functions.

2. Synthesize transmitted signals (programmable levels).

3. Provide system master timing source.
The core of the analog front end is the 89027 chip (U1). The filter functions are performed
internally using CMOS switched capacitor technology. Transmitted signal synthesis is
achieved using digital to analog conversion techniques. An internal oscillator in
conjunction with crystal Y1 furnishes the master timing source. Signals connected
between Ui and U2 (application specific processor) form a digital serial link that allow the
two system elements to 'talk' back and forth.

Application Specific Processor
The application specific processor (89026 U2) performs all of the 'intelligent' functions of
the modem. Its functions are:

1. Analyze and execute commands.

2. "Control/monitor DAA.

3. Support NVRAM.

4. DTE handshaking functions.

5. Relay information to/from analog front end.

The 89026 is a high speed 16 bit microcontroller in a 68 pin PLCC package. Its program,
residing in internal masked ROM, controls all modem functions. It is a self contained,
single chip, device that needs only a clock (provided by Ul) and power to operate.

NVRAM
NVRAM stands for Non Volatile Random Access Memory. Its purpose is to retain
important configuration options even while power is off. This design uses a serial device
(93C46 U3). The system controller (U2) modifies the contents of this device in
accordance with software configuration commands (&Wn).

RS-232 Interface
This section furnishes level conversion (TTL to RS-232), connection options, and status
indicators. U7 is an RS-232 receiver (1489) while U8 is an RS-232 line driver (1488). J3
is a shunt arrangement that, when removed, 'disconnects' the modem from the edge
connector (P1). This option is useful when cable connection (via J14) is desired. Level
translator/buffer U8 (2588) allows the status indicator LED's to be driven from the -12V
supply. This reduces current consumption on the positive supply, making the two a little
more symmetrical.

MAINTENACE

Preventive Maintenance
This device requires no preventive maintenance.

Alignments
This modem is self aligning using a technique called adaptive equalization.

Trouble Analysis
The G.D.I. Model SM2400 is fully tested over temperature prior to shipment, however,
rare circuit failures do occur for a variety of reasons. A Troubleshooting Flowchart and a
written Test Procedure are included to aid in fault isolation. Also, it should be noted that,
many "problems" are caused by improper connections and/or noisy phone lines.

Trouble Analysis Special Considerations
All modems that are intended to connect to dial-up lines are required to conform to FCC
part 68 regulations. This means special testing by the manufacturer must be performed to
ensure compliance. For this reason GDI recommends that no attempt at repairing the
DAA section of the modem should be made by the user.

Waveforms and Voltage Measurements
The modem is purely digital in nature. All logic signals conform to TTL standards. All
serial I/O signals conform to RS232 standards. Voltage measurements of the power
supplies should be within 5% of nominal.

TEST PROCEDURE

The following test procedure is outlined as a minimum effort to ensure correct modem
operation. It relies on a diagnostic capability of the modem called analog loopback in
which the modem communicates with itself. More thorough testing requires highly
specialized equipment and is beyond the scope of this document.

EQUIPMENT REQUIRED

1. Dumb terminal or computer with terminal emulation software.

2. Cable to interface terminal to modem. (DB-9S to DB25S)

3. 170 traffic controller with no cards installed.

4. Access to standard dial-up telephone line.

PREPARATION

1. Configure terminal device for 1200 baud, 7 data bits, 2 stop bits and even parity.

2. Connect interface cable between the terminal and J14.

3. Connect phone line to RJ11 jack "LINE".

4. Install modem in modem slot of controller.

5. Power up terminal.

BEGIN TEST

1. Power up controller observing LED's on front edge of modem. After modem
initialization, lamps labeled AA and DCD should be on. (If not, see Shipping
Configuration.)

2. Enter ATS18=0&T1 <return> on the terminal. This enables the Local Analog
Loopback mode.

3. The modem is now essentially connected to itself. Characters typed at the
keyboard are sent through modulator and demodulator sections of the modem and
returned to the terminal. Therefore characters seen at the terminal should be exactly those
typed. Type a message with many different characters such as "the quick brown fox jumps
over the lazy dog". Verify that what is seen on the screen is exactly what was typed.
Verify that, while typing, the TXD and RXD lamps flash.

4. Type +++ <no return>. This should cause the modem to respond with "OK" and
return to command mode.

5. Enter AT&T0 <return> ending the test. Modem should respond "OK".

6. Call the modem from a remote phone. The modem should answer the call (OH
light on), respond with "RING" on the terminal, and you should hear a tone. After around
30 seconds the modem should hang up (OH light off) and respond "NO CARRIER".

7. Type ATDPn <return> where n is the phone number of the remote phone. The
modem should go off hook and pulse dial the number. The remote phone should ring.
Answer it! It's for you. You should hear nothing on the phone, but after around 30 seconds
the modem will hang up and respond "NO CARRIER".

END OF TEST

COMMAND SET

The call set-up and user option commands for the Model SM2400 are designed to be
compatible with the Hayes Smartmodem 2400. The following paragraphs explain the
functional groups and the function of each of the user options. One configuration option is
assigned a switch setting and is referred to as an 'adjustment'. These options will configure
the modem for the basic operating modes. The software commands can be issued from an
ASCII terminal in serial mode, or from a microcomputer through a DART or USART.
These commands allow the user to personalize the modem to his or her environment. Nine
of the twenty-seven commands can be saved in a non-volatile RAM.

SOFTWARE CONFIGURATION COMMANDS

This section lists all the Model SM2400 codes, commands and registers, that may be used
while configuring the modem. Commands instruct the modem to perform an action, the
value in the associated registers determine how the commands are performed, the result
codes returned by the modem tell the user about the execution of the commands.
The following paragraphs arrange the codes into functional groups. The commands are of
four basic types, dialing, answering, standard functions, and special functions.
The commands can be entered in a string, with or without spaces, any spaces within or
between commands will be ignored by the modem. During the entry of any command, the
"delete" or "backspace" key can be used to correct any error. Upper case or lower case
characters can be used in the commands. Some exceptions to this rule are mentioned in
association with the specific commands.
All the commands described in the following paragraphs refer to asynchronous terminals
using ASCII codes.

(AT) Attention Code

The attention code, ‘AT’, begins every command line except A/. AT may be entered as
upper or lower case characters, and cannot be deleted using backspace or delete keys.
More than one command can be placed on a single line and separated with spaces for
readability. The command line must end with the ASCII character stored in S Register 3,
which defaults to decimal 13 (Carriage Return). A line with no carriage return will be
ignored. Commands following the AT are processed after receiving the carriage
return character. This attention code is used by the modem to detect the bit rate and
character format of the connected DTE.

(A) Answer Command

This command causes the modem to go off-hook and take control of the telephone line (in
answer mode), from the telephone set. After receiving this command the modem cannot
accept any more commands, as it immediately answers the call and goes into the data
transmission mode. While in the data mode the Escape code (+++) will return the modem
to the command mode.

(A/) Repeat Command

AT does not precede this command. The repeat command instructs the modem to repeat
the execution of the last command line stored in the command buffer. The repeat
command can be used to redial a number if busy. This command is neither followed by
carriage return, nor preceded by the attention command AT. THE COMMAND BUFFER
IS LOST AFTER A CONNECTION IS MADE. While the modem is connected, the
'escape state' command buffer is purged. This causes the last number dialed to be lost.

(Bn) BELL/V.24 Protocol Compatibility

The B command selects the protocol for 1200 and 300 bps operation. This command
selects the mode of the data set, between CCITT and Bell modes. The command is
ignored when the modem operation is at 2400 bps. BO sets the modem to CCITT modes
V.22 bis (1200 bps) and V.21 (300 bps). The default B1 sets the modem to Bell modes
212A (1200 bps) and 103 (300 bps).
CCITT mode V.22 bis sends 2100 Hz for 3.3 seconds and 75 mS of silence followed by
unscrambled ones in the answer mode, while the BELL 212A protocol simply sends 2225
Hz.
The transmitted signal in the originate mode sends scrambled ones at 1200 bps for both
V.22 bis and Bell 212A.

(Dstring) The Dialing Commands

The Dstring command causes the modem to go to the auto-dial mode in switched line, or
to originate a call in leased line. The parameters for 'string' include S=n(stored string),
digits 0 to 9, touch-tones A to D, *, #, the period and slash, P, R, T, comma and
semicolon. Punctuations (parenthesis, hyphen, and spaces) entered for readability are
ignored. Modifiers are described below.

P,T These commands select between the pulse and tone dialing for the succeeding

digits to be dialed. With either P or T type dialing command, the dialing begins
after the timeout period defined by register S6.

, The comma causes the modem, while dialing, to pause for the time specified by

register S8 (default is 2 seconds). This parameter is used for example, to pause
between dialing an external access code from a PBX, and then dialing the
desired number.

; The semicolon placed at the end of a dial command places the modem in

command state after dialing. It does not provide connection with another modem,

but holds the line for further commands. The modem asserts that it has finished

dialing by returning the result code `OK'. This command is useful in dialing long

numbers.

@ The @ command causes the modem to wait for the time specified by register S7

for one or more rings, followed by 5 seconds of silence before going to the next

symbol in the dialing string. S7 default is 30 seconds.

! The flash command causes the modem to go on-hook for 1/2 second. Flash might

be used for transferring calls.

S,S=n Dial string stored in NVRAM (See &Zn=string). ATDS will dial stored string O.

ATDS=n will dial stored string n where n is 0 through 3.

R The Reverse command at the end of dialing permits the establishment of a call in

reverse mode, i.e., the local modem, which originated the call enters the "answer'

mode. This would be a useful command for communicating with an `originate

only' modem at a remote site.

W Causes modem to wait for a dial tone while dialing.

(En) Echo Command

The Echo command determines whether the modem will echo the characters sent to it
while in the command state. E1 causes the modem to echo, which is the system default,
and EO sets the modem to no echo.

(Hn) Switch Hook Control

The H or HO (default) command will cause the telephone line relay to disconnect (hang
up). The H1 command will cause the telephone line relay to go off-hook.

(In) Request Product Code and Checksum

The I command requests the product code. The Model SM2400 will respond with 24x
where x is the software revision level. The command Ii will cause a checksum to be
computed on the internal ROM and returned as three ASCII numeric characters followed
by a carriage return, line feed. The 12 command returns a computed checksum with a
response of OK or ERROR.

(Ln) Speaker Volume

L,L0,L1 Low Volume
L2 Medium Volume (default)
L3 High Volume
Example: ATL3 (Sets the speaker volume to high)

(Mn) Monitor On/Off

M speaker is off MO speaker is off
M1 speaker is off while receiving carrier (default)
M2 speaker always on
M3 speaker disabled while dialing or receiving carrier

(On) On-Line

The 0 command is used to return the modem to the on-line mode, after temporarily
bringing it to the command mode by using the escape code (+++). 01 will cause the
modem to return to the online state and initiate a retrain sequence (2400 bps only). Issuing
an ATO from an off-line idle state will evoke a "NO CARRIER" response. ATO issued
from the call progress mode (after an "ATDxxxxx;" which puts the modem in a command
state after dialing) causes the modem to remain in the originate mode.

(Qn) Result Codes

The Q command turns on and off result codes during execution of commands. The code
QO (default) enables the result codes to be sent. When set to Ql, the modem will not
return result codes. S register values, identification codes, checksum results, and results of
test modes with self tests are returned.

(Sr) Direct Register Commands

Sr? Returns current decimal value of S register r.
Sr=n Writes the 8 bit binary equivalent of n (0-255 decimal) to S register r.

Modem configuration variables are kept in 8 bit storage elements called "S registers".
Some registers are dedicated to one function while others share the 8 bits to store
information about the status of different commands (bit mapped). For an intelligent 'Host',
it may be easier to directly write the desired data into the S registers rather than going
through the longer process of stepping through each command. Understanding these
registers allows the user to configure the modem at any time, and to change only the
desired parameters.

(Vn) Verbal/Numeric (Verbose/Terse)

The Vn command selects the type of result codes returned by the modem after or during
the execution of commands. V1 selects word result codes (default). VO selects digit result
codes.

Result Codes Returned by Modem

Meaning Short Form Long Form

Command Line Executed Without Errors 0 OK
Connected at 300 bps 1 CONNECT
Local Telephone Line Ringing 2 RING
Carrier Lost or Never Received 3 NO CARRIER
Error in Command Line 4 ERROR
Invalid Command Line
Line Length Exceeds Buffer Size
Invalid Character Format
Connected at 1200 bps 5 CONNECT 1200
No Dial Tone Received Within Time-Out 6 NO DIAL TONE
Called Line Busy 7 BUSY
No Answer Within Time-Out 8 NO ANSWER
Connected at 2400 bps 10 CONNECT 2400

Long form results are preceded and terminated with both carriage return and line feed
characters. Short form codes are only terminated with a carriage return.

(Xn) Enable Extended Result Code

Forms of this command can have an effect on Long Form CONNECT messages, Dialing
(Blind or Wait for Dial Tone), and BUSY detection. 'Blind' dialing means that the modem
goes off-hook and waits a time period specified by register S6 before dialing regardless of
the presence or absence of dialtone. Wait for Dial Tone dialing means that the modem
goes off hook and waits the time period specified by register S6 to receive a dial tone
before dialing. If no dial tone is received within the allotted time, the modem returns NO
DIAL TONE.

X or XO Connect Message - CONNECT
Dialing - Blind (set S6 before dial)

Dial Tone Timeout - No
Busy Detection - No

X1 Connect Message - Full Message

Dialing - Blind Dial Tone Timeout - No
Busy Detection - No

X2 Connect Message - Full Message

Dialing - Waits for Dial Tone

Dial Tone Timeout - Yes (5 seconds fixed)

Busy Detection - No

X3 Connect Message - Full Message

Dialing - Blind
Dial Tone Timeout - No
Busy Detection - Yes (modem will return BUSY)

X4 (default) Connect Message - Full Message

Dialing - Waits for Dial Tone
Dial Tone Timeout - Yes (S6)
Busy Detection - Yes

(Yn) Enable Long Space Disconnect

Y or YO (default) disables this option. Yl sets the modem to disconnect when a space of

1.6 seconds or more is received from the remote modem. Also, under Yl, a space of 4
seconds is sent prior to going on-hook upon receiving a HO command or detecting an ON
to OFF transition on DTR if &D option is selected.

(Zn) The Reset Command
This command causes a reset and a recall of the profile that was saved in NVRAM by the
&Wn command and then returns 'OK'.
Valid forms: ATZ or ATZO - recalls profile 0 (same as power up)

ATZ1 - recalls profile 1

Any subsequent characters in the command line will be ignored.

(+++) The Escape Code

The escape code returns the modem to the command state from the online state, without
releasing the telephone line. This command consists of an escape guard time (S12 default
1 second) and an escape character (ASCII code in S2 default '+'). The escape character
must be issued three consecutive times with a guard time before and after the characters.
If the sequence is successful, the modem responds 'OK' and enters an 'escape' command
state.

(&Cn) DCD Options

&C or &CO maintains a DCD ON condition and ignores the actual state of the data
carrier from the remote modem. &C1 (default) causes DCD to reflect remote carrier
status.

(&Dn) DTR Options

&D or &DO causes the modem to ignore DTR. After the &D1 command the modem will
go from data mode to command state on an ON to OFF transition of DTR. For &D2
(default) an ON to OFF transition of DTR will cause the modem to go on-hook, disable
auto-answer, and end in the command state. &D3 causes the modem to reset (see Zn
command) if it detects an ON to OFF transition of DTR. DTR transitions during idle state
will not generate any result codes or have any other effect on the modem.

- Any ON to OFF state change in DTR must last longer than the period specified by S25
in order to be recognized.

(&F) Fetch Factory Configuration Profile

Configures modem with defaults contained in ROM. This is the easiest way to reconfigure
the modem into a known state. This command does not modify NVRAM (see &Wn). The
following is a list of conditions following the &F command.

2400 baud communications rate Bell 212A
Even parity
Auto answer disabled
Command echo on
All result codes enabled
Wait for dial tone before dialing Busy signal detect
Full word result codes
Pulse dial make/break ratio 39/61 Test timer set to zero
CTS follows RTS after delay in S26 RTS to CTS delay 10 mSec
DTR transition causes disconnect DCD reflects remote carrier status DSR always ON
Long space disconnect disabled
Speaker enabled (off while receiving carrier)
Speaker volume set to medium
Will grant remote digital loopback request
Guard tones disabled
Minimum DTR pulsewidth is 50 mSec Ring counter set to zero
Escape code character 43 (+)
Carriage return character 13 (carriage return)
Line feed character 10 (line feed) Backspace character 08 (backspace) Wait for dial tone
is 2 seconds
Wait for carrier after dialing is 30 seconds
Dial pause (comma) is 2 seconds
Carrier detect response time is 600 mSec Lost carrier to hang up delay is 1.4 seconds
Escape code guard time is 1 second

(&Gn) Guard Tone Options

&G or &GO (default) no guard tone
&G1 550 Hz guard tone
&G2 1800 Hz guard tone

(&Jn) Telephone Jack Selection

&JO and &J1 commands are accepted by the modem but have no function. They are
reserved for a future switching implementation.

(&Ln) Leased/Dialup Line Selection

The &L or &LO (default) command selects dialup line. &L1 selects leased line.

(&Mn) Async/Sync Mode Selection

&M or &MO (default) selects asynchronous mode. The &Mi, &M2, and &M3 commands
are reserved for future synchronous mode implementations. They will cause an ERROR
response from the modem but will not affect operation.

(&Pn) Make/Break Pulse Dial Ratio

The make/break ratio for &P or &PO is 39% make and 61% break, U.S. standard. The
&P1 command sets the ratio at 33%/67%, compatible with the U.K. and Hong Kong.

(&Rn) RTS/CTS Options (Request to Send/Clear to Send)

The &R or &RO (default) command sets CTS to respond to RTS. CTS will turn ON in
response to an OFF to ON transition of RTS after a delay specified by S26 (default 10
mSec). The &R1 command is reserved for future synchronous mode implementation.
Attempts at &R1 will invoke an ERROR response from the modem but will have no
effect on operation.

(&Sn) DSR Options (Data Set Ready)

The &S or &SO (default) command causes DSR to remain ON at all times while the
modem has power. Command &S1 will cause DSR to operate in accordance with CCITT
V.22 bis/V.22 recommendation.

(&Tn) Test Commands

The &T or &TO command will terminate any test in progress. The &Tn command should
always be the last command in any given command line.
The &T1 command will initiate Local Analog Loopback. This is used to verify the path
which includes the local modem and the local data terminal equipment. S register 18 (test
timer) or &TO can be used to terminate a test.

Test &T1 example:
S18 is the test duration timer

ATS18=O&T1 Test time of 0 allows the test to run continuously;

&T1 starts the test.

the quick brown fox jumps... User message

+++ Escape sequence

OK Modem acknowledges +++

AT&T0 Ends test

OK Test complete

The command &T3 will initiate a Local Digital Loopback. This allows data being sent
from the remote modem to be looped back, in the digital section of the local modem, and
sent back to the remote modem. This mode allows the remote modem to run a remote
digital loopback test. Both modems must be connected before this test can start.

Test &T3 example:

+++ Escape

OK Acknowledgement

ATS18=O&T3 Puts local modem in digital loopback

OK Loopback mode

Operator performs tests from the remote modem at this point

AT&T0 Terminate digital loopback

OK Test ended

The command &T4 (default) allows the modem to grant a request from the remote
modem for a Remote Digital Loopback.
The command &T5 prohibits the local modem from granting a request from a remote
modem for a Remote Digital Loopback.
The command &T6 is used to test the local data terminal equipment, remote and local
modems, and the telephone circuit. The local modem sends a 'request for digital loopback'
message to the remote modem. If conditioned, (see &T4,&T5) the remote modem will
send back whatever it receives until the test is ended. Both modems must be connected
before this test can start. Note: The &T6 command works at 1200 or 2400 baud only.

Test &T6 example:

+++ Escape

OK Acknowledgement

ATS18=0&T6 Test started

the quick brown... Test message

+++ Escape

OK Acknowledge escape

AT&T0 End test

OK Test complete

The command &T7 starts a Remote Digital Loopback with Self-Test in accordance with
CCITT Recommendation V.54. During the test phase, an internally generated data pattern
of alternating ones and zeros at the selected bit rate is applied to the scrambler. An error
detector capable of identifying errors is connected to the output of the descrambler. At the
end of the test a three-digit error count from 0 to 255 is displayed. Both modems must be
connected before the test can start.

Test &T7 example:

+++ Escape

OK Modem Acknowledges

ATS18=0&T7 Start test

AT&T0 End Test

000 Zero errors

OK Test acknowledgement

The command &T8 starts a Local Analog Loopback with Self-Test in accordance with
CCITT Recommendation V.54. During the test, an internally generated data pattern of
alternating ones and zeros at the selected bit rate is applied to the scrambler. An error
detector capable of identifying errors is connected to the output of the descrambler. At the
end of the test a three-digit error count from 0 to 255 is displayed. If the modem is on line
when the test starts, carrier will be lost. This test is useful for checking the local modem
transmit and receive circuits.

Test &T8 example:

ATS18=0&T8 Start test

AT&T0 End test

000 No errors

OK Acknowledgement

(&Wn) Write Configuration to NVRAM

The &Wn command saves a subset of the S registers in one of two profiles in NVRAM.
&W or &WO stores the current configuration in the first profile. &W1 stores current
parameters in the second. The first profile is restored automatically whenever the modem
is turned on, or upon issuing the Z or ZO command. The second profile may be restored
by the Z1 command. Registers saved are: SO, S14, S18, S21, S22, S23, S25, S26 and S27.
Note: If the &Wn command is issued while in the escape state, an ERROR message will
be returned, and the current configuration will not be saved.

(&Zn=string) Store Telephone Number

The &Zn=string command is used to store one of four (n=0,1,2,3) telephone numbers
(into NVRAM) for dialing at a later time using the DS=n dial stored number command.
'String' represents an ASCII string composed of dial digits plus optional modifiers. Dial
digits may include 0 - 9 (pulse or tone dial) and A,B,C,D,#,and * (tone only). Possible
modifiers include comma,T,P,R,W,!,@, and ; as described in Dstring command. Up to 33
characters may be stored. Unrecognized characters such as space, dash, and parenthesis
are ignored and need not be included in the count. If more than 33 recognized characters
are supplied, the dial string will be truncated to 33. If the &Zn=string command is issued
in the escape state, an ERROR message will be returned and no dial string will be stored.
If parameter n= is omitted, 0 is assumed.

Example 1:

AT&Z T 555-1212 stores T5551212 into NVRAM location Zero.

OK modem acknowledges
ATDS dial stored string Zero
T5551212 modem acknowledges and dials

Example 2:

AT&Z2=T1(602)961-2997 stores T16029612997 into NVRAM location 2.

OK modem acknowledges

The number stored by the preceding command may be dialed from the command state by:

ATDS=2 dial stored number in location 2.
716029612997 modem acknowledges and dials

CONFIGURATION (S) REGISTERS

The Model SM2400 incorporates 8 bit storage elements called S Registers. These registers
contain information that control modem operating parameters. Some registers are
associated with particular functions while others have groups of bits assigned to different
functions. A subset of these registers may be stored in NVRAM (see &Wn). Rather than
stepping through many discrete commands, the user may find it easier to modify modem
operating parameters by writing directly to S Registers. The registers can be read by "Sr?"
and written by "Sr=n," where n is the ASCII decimal value of the digit(s) to be written,
and r is the register number to read or write. Example:

ATS0=1 Writes a one to S register zero

(Allows modem to auto-answer on first ring)

ATSO? Will display contents (decimal) register zero

SO - Ring to Answer

The contents of this register determines the number of rings that must occur before the
modem will automatically answer a call. Allowable range is 0 to 255. Setting this register
to 0 will disable auto-answer. Setting this register to n (non zero) will cause the modem to
auto-answer on the nth ring.

SI - Ring Count

S1 is incremented by one each time the modem detects a ring signal. S1 is zeroed if no
rings occur over any eight second period.

S2 - Escape Code Character

This register holds the ASCII decimal value of the escape code character. S2 can be set to
any value from 0 to 255, but values greater than 127, without an ASCII equivalent, will
completely disable the escape function. If the &D1, &D2, or &D3 option is in effect, the
modem will return to the escape command state on an ON to OFF transition of DTR. S2
default value: 43 (ASCII +)

S3 - Carriage Return Character

This register contains the ASCII decimal value of the carriage return or end of line
character. This character terminates both command lines and result codes. Allowable S3
range is 0 to 127. S2 default value: 13 (ASCII carriage return)

S4 - Line Feed Character

This register stores the ASCII decimal value of the line feed character, which is output
after the carriage return character, when the modem is returning word result codes.
Allowable S4 range is 0 to 127. Default value: 10 (ASCII line feed, CTRL J)

S5 - Backspace Character

This register holds the backspace character. When the modem receives the character
defined by this register, it performs these four steps: 1. Echo the backspace character. 2.
Sends an ASCII space. 3. Sends the backspace character a second time. 4. Deletes the last
character in the command buffer. A typical command line can be backspaced until the T
of the AT is reached. If an attempt is made at backspacing over the T, the modem will
echo the backspace character and send an ASCII "T", but will not delete the "T" from the
command buffer. The backspace character should not be set between 33 and 126, the
range of printable ASCII characters. Allowable S5 range; 0 to 32 and 127. Default value:
8 (ASCII back space, CTRL H)

S6 - Wait for Dial Tone

This register defines the maximum amount of time the modem waits after 'off-hook'
before dialing. In all cases, the modem waits for a minimum of 2 seconds even if S6 is set
to a lower value. Allowable S6 range is 0 to 255 seconds. The "wait for dialtone" call
progress monitoring feature will override the value in S6 and dial the first digit upon
detection of a dial tone. Default value: 2 (seconds)

S7 - Wait for Carrier after Dial

In originate mode, extended result code options X3 or X4 allow S7 to establish the time
that the modem waits (after dialing) for the answering modem to go off-hook (ringback).
Once the answering modem goes off-hook, the originating modem then uses S7 to deter­mine how long to wait for a carrier before terminating the call. This could result in a total
wait time (dial to connect) of up to twice the value in S7. In answer mode, S7 is used as
an abort timer. When an answering modem goes off-hook, it sends a carrier and expects
one in response. If no response is received before S7 has elapsed, the answering modem
will terminate the call.
If leased line operation is selected S7 has no effect, and the modem will wait indefinitely
for the carrier. The operators at each end of the leased line will have sufficient time to
establish the connection. Default value: 30 (seconds)

S8 - Pause Time for the Comma Dial Modifier

Register S8 contains the pause time for the comma (,) in a dialing string. S8 range is 0 to
255 (seconds). Default value: 2

S9 - Not Used

S10 - Lost Carrier to Hang Up Delay
This register defines the duration between loss of carrier and the initiation of a disconnect
sequence (if configured for loss of carrier disconnect). The unit of time is 100's of
milliseconds (tenths of seconds). If S10 is set to 255, the modem will ignore carrier detect
status and assume that the carrier is always

present. Allowable values are 1 to 255. Any loss of carrier will result in a disconnect if
register S10 is smaller than S9. The actual length of loss of carrier is the delta between
S10 and S9. Default value: 1.4 seconds

S11 - DTMF Duration and Spacing
Register Sil allows for adjustable tone-dialing duration and spacing. The duration of a
tone is always equal to the "quiet" interval (spacing) between tones. Sil can be set to any
value between 50 and 255 (milliseconds). The default value is 100. Sll is not saved in
NVRAM with the &Wn command. An attempt to set Sil to a value less than 50 will result
in 50 being stored.

S12 - Escape Code Guard Time
This register controls the time delay required immediately before and after the three
escape code characters. The guard time is in units of 20 mS and has a maximum value of

5.1 seconds (255 * 20mS). Time between the three escape code characters must be less
than the guard time in order for the escape sequence to be valid. Allowable values for S12
are 20 to 255. If guard time is defined as 0, the timing will not be a factor, but the
characters must still occur consecutively. Default value: 1 second

S13 - Not Used
S14 - Bit Mapped Options

7 6 5 4 3 2 1 0

Not Used

0 Local Echo Disabled

1 Local Echo Enabled (Default)

0 Result Codes Enabled (Default)

1 Result Codes Disabled

0 Result Codes as Digits

1 Result Codes as Words (Default)

0 Smart Mode (Default)

1 Dumb Mode
(Bit 4 reflects status of switch 6 on power up or Z
command)

0 Tone Dial

1 Pulse Dial (Default)
(Based on dialing mode of the last string dialed.)

Not Used

0 Answer Mode

1 Originate Mode (Default)
(Also see A,D and R commands)

S15 - Not Used

S16 - Modem Test Options

7 6 5 4 3 2 1 0

0 Local Analog Loop Disabled (Default)

1 Local Analog Loop Enabled

(See &T1 command)

Not Used

0 Local Digital Loop Disabled (Default)
1 Local Digital Loop Enabled
(See &T3 command)

0 Loopback Off (Default)

1 Loopback On (Remotely Initiated)
(See &T4 and &T5 commands)

0 Disable Remote Digital Loop (Default)

1 Initiate Remote Digital Loop
(See &T6 command)

0 Disable Remote Self-Test (Default)

1 Initiate Remote Self-Test
(Digital Test: See &T7 command)

0 Disable Local Self-Test (Default)

1 Enable Local Self-Test
(Analog Test: See &T8 command)

Not Used

This register not saved in NVRAM

S17 - Not Used

S18 - Test Timer

If S18 is set from 1 to 255 seconds, an &Tx command will time-out when this time has
elapsed, automatically ending the test. &TO will stop the test before S18 has counted
down. If S18=0, tests will run continuously and &TO must be used to end the test. Default
Value: 0 (continuous)

S19 - Not Used

S20 - Not Used

S21 - Bit Mapped Options

7 6 5 4 3 2 1 0

Not Used

Not Used

0 CTS follows RTS (Default)
(See &R command)

BIT4/BIT3 (See &Dn command)

0/0 Modem Ignores DTR
0/1 Command State ON to OFF DTR
1/0 Hangs Up ON to OFF DTR (default)
1/1 Initialize ON to OFF DTR

0 DCD Always ON

1 DCD Indicates Valid Carrier (default)
(See &Cn command)

0 DSR Always ON (Default)

1 CCITT V.22 bis/V.22 (&Sn)

0 Disable Long Space Disconnect (Default)

1 Enable Long Space Disconnect
(See Y command)

S22 - Bit Mapped Options

7 6 5 4 3 2 1 0

BIT1/BITO (See L command)
0/0 Undefined
0/1 Low Speaker Volume
1/0 Med Speaker Volume (Default)
1/1 Hi Speaker Volume

BIT3/BIT2 (See M command)

0/0 Speaker Disabled
0/1 Speaker On Until Carrier (Default) 1/0 Speaker Always On
1/1 Speaker On Until Carrier but Off During Dial

BIT6/BIT5/BIT4 (See X command)
0/0/0 CONNECT, Blind Dial, No Busy Detect
0/0/1 Undefined
0/1/0 Undefined
0/1/1 Undefined

See X1 command 1/0/0 Full Codes, Blind, No Busy Detect
See X2 command 1/0/1 Full Codes, Wait, Timeout, No Busy
See X3 command 1/1/0 Full Codes, Blind, Busy Detect
See X4 command 1/1/1 Full, Wait, Busy (default)

0 U.S. Pulse Dial Ratio (Default)
1 U.K./ Hong Kong Pulse Dial Ratio

(See &P command)

S23 - Bit Mapped Options

7 6 5 4 3 2 1 0

0 Ignore Remote Loopback Request
1 Accept Remote Loopback Request (Default)

(See &T4 and &T5 commands)

BIT2/BIT1 Baud Rate (See AT command)

0/0 0 to 300 bps
0/1 invalid
1/0 1200 bps
1/1 2400 bps

Not Used

BIT5/BIT4 Parity (See AT command)

0/0 Parity Even (Default)
0/1 Parity Space
1/0 Parity Odd
1/1 Parity Mark (None)

BIT7/BIT6 (See &G command)

0/0 No Guard Tone (Default)
0/1 550 Hz Guard Tone
1/0 1800 Hz Guard Tone
1/1 Undefined

S24 - Not Used

S25 - DTR Response Time

For DTR option &D1 this register specifies the amount of time DTR must be OFF in
order to return the modem to command mode. For default &DO (ignore DTR) mode this
register is disregarded. S25 units are tens of milliseconds. Default value 5 (50 mSec)

S26 - RTS to CTS Delay Interval

This register is reserved for a future synchronous mode implementation.

S27 - Bit Mapped Options
7 6 5 4 3 2 1 0

BIT1/BITO (See &M command)
0/0 Asynchronous (Default)

0 Dialup Line (Default)
1 Leased Line
(See &L command)

Not Used

BIT5/BIT4 Reserved to define future synchronous mode timing source

0 CCITT V.22 BIS/V.22

1 BELL 212A (Default)
(See B command)

Not Used

OPTIONS NOT SAVED IN NVRAM

Ring Counter………………………………………………………………………….00
Escape Code Character……………………………………………………………….43
Carriage Return Character……………………………………………………………13
Line Feed Character………………………………………………………………….10
Back Space Character……………………………………………………………….. 08
DTMF Duration/Spacing………………………………………………………100mSec
Duration of Wait for Dial Tone……………………………………………………2 Sec
Duration of Wait for Carrier after Dialing………………………………………..30 Sec
Duration of Pause for the Comma Dial Modifier………………………………….2 Sec
Carrier Detect Response Time…………………………………………………...0.6 Sec
Lost Carrier to Hang Up Delay…………………………………………………..1.4 Sec
Escape Code Guard Time………………………………………………………….1 Sec

OPTIONS SAVED IN NVRAM (&W)

Baud Rate…………………………………………………………………300,1200,2400
Parity…………………………………………………………odd,even,mark,space,none
Answer on nth ring………………………………………………………………1 to 255
Auto-Answer………………………………………………………………enable/disable
Command echo…………………………………………………………….enable/disable
Result Codes……………………………………………………………….enable/disable
Result Codes………………………………………………………………..verbose/terse
Dialing………………………………………………………………………pulse/DTMF
Test Timer……………………………………………………………….0 to 255 seconds
RTS/CTS option
RTS/CTS delay time DTR circuit option DCD circuit option DSR circuit option
Long Space Disconnect…………………………………………………….enable/disable
Speaker Volume
Pulse Dial Ratio
Grant/deny Remote Digital Loop
Guard tone option
Minimum DTR pulsewidth
Dialup/Leased line

COMMAND SUMMARY

AT - Defines baud rate and precedes command line
A/ - Re-executes last commandA

A - Modem goes off-hook in answer mode

B - Sets CCITT V.22 operation when at 1200 bps
B1 - Sets Bell 212A operation when at 1200 bps

Dstr - Dial string following D in command line

E - Modem does not echo commands
El - Modem echoes commands back to terminal

H - Modem goes on hook (Hangs up)
Hi - Modem goes off hook

I - Display product code
I1 - Display checksum of internal ROM
I2 - Validates internal ROM

L,L1 - Speaker Volume low
L2 - Speaker Volume Medium
L3 - Speaker Volume Hi

M - Speaker off
Ml - Speaker on until carrier detected
M2 - Speaker always on
M3 - Speaker on until carrier detected except when dialing

O - Return on-line
O1 - Return on-line with retrain

Q - Modem returns result codes
Q1 - Modem does not return result codes

Sr=n - Set register r to decimal value n
Sr? - Display decimal contents of S register r

V - Short numeric result codes
V1 - Full result codes

X - CONNECT, result code enabled
X1 - CONNECT BBBB, codes enabled,blind,no busy detect
X2 - CONNECT BBBB, codes enabled,wait,no busy detect
X3 - CONNECT BBBB, codes enabled,blind, busy detect
X4 - CONNECT BBBB, codes enabled,wait,busy detect

Y - Long space disconnect disabled
Y1 - Long space disconnect enabled

Zn - Load profile n stored in NVRAM

&C - DCD always ON
&C1 - DCD ON if carrier present

&D - Modem ignores DTR
&D1 - Assume command state (ON to OFF DTR)
&D2 - Command state,hang up,disable Auto-Answer (ON to OFF DTR)
&D3 - Initialize (ON to OFF DTR)

&F - Load factory configuration profile

&G - No guard tone
&G1 - 550 Hz guard tone
&G2 - 1800 Hz guard tone

&J - RJ11 type telco connection
&J1 - Reserved

&L - Dialup line
&L1 - Leased line

&M - Asynchronous mode
&M1 - Reserved
&M2 - Reserved
&M3 - Reserved

&P - Pulse dial ratio U.S.
&P1 - Pulse dial ratio U.K./Hong Kong

&R - CTS follows RTS
&R1 - Ignore RTS, CTS always ON

&S - DSR always ON
&S1 - DSR compatible V.24

&TO - End a test in progress
&T1 - Initiate local analog loopback test
&T2 - Not Used
&T3 - Initiate digital loopback
&T4 - Grants remote digital loopback request
&T5 - Denies remote digital loopback request
&T6 - Initiate remote digital loopback test
&T7 - Initiate remote digital loopback self-test
&T8 - Initiate local analog loopback self-test

&Wn - Write current configuration to NVRAM profile n
&X - Modem sources future synchronous transmit clock
&X1 - Reserved
&X2 - Reserved

&Zn - Store a phone number n in NVRAM