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Contents:

Welcome to 56K Information Access

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Glossary

Regulatory Information

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56K Faxmodem User's Guide and Reference

Technical Reference

Front Panel Lights

Symbol
Meaning
Status
PWR Power The modem is turned on.
CD Carrier Detect ON if modem receives a valid data signal (carrier) from a remote modem, indicating that a data transmission is possible. Always ON if CD override is ON (&C0).
RD Received Data Flashes when modem sends result codes or passes received data bits from remote.
SD Send Data Flashes when computer sends a data bit to modem.

 

Typing Commands

  • In terminal mode, type commands in either upper or lower case, not a combination. Use the Backspace key to delete errors. (You cannot delete the original AT command because it is stored in the modem buffer.)
  • If a command has numeric options and you do not include a number, zero is assumed. For example, if you type ATB, the command ATB0 is assumed.
  • Every command except A/, +++, and A> must begin with the AT prefix and be entered by pressing ENTER.
  • The maximum command length is 58 characters. This does not include the AT prefix, carriage returns, or spaces.

All defaults are based on the &F1*Hardware Flow Control template loaded in NVRAM when the modem is shipped. Defaults are listed in italics.

Basic Data Commands

<control key>S

Stop or restart help screens.

<control key>C or <control key>K

Stop help screens.

$ Use in conjunction with D, S, or & commands (or just AT) to display a basic command list; online help.

A Manual Answer goes off hook in answer mode. Pressing any key aborts the operations.

A/ Re-executes the last issued command. Used mainly to redial. This does not require the AT prefix or a Carriage Return.

A> Re-executes the last issued command continuously, until the user intervenes or the command is executed forever. Does not require the AT prefix or a Carriage Return.

Any key Aborts off-hook dial/answer operation and hangs up.

AT Required command prefix, except with A/, +++, and A>. Use alone to test for OK result code.

Bn U.S./ITU-T answer sequence

BO ITU-T answer sequence
B1 U.S. answer tone

Dn Dials the specified phone number, includes the following:

0-9 Numeric digits
#, * Extended touch-tone pad tones
L Dials the last dialled number
P Pulse (rotary) dial
R Originates call using answer (reverse) frequencies
Sn Dials the phone number string stored at position n (n = 0*3). Phone numbers are stored with the &Zn=s command
T Tone dial

Dn (Comma) Pause, see the definition of the S8 register to which it is linked

; (Semicolon) Return to Command mode after dialling
! (Exclamation point) Flashes the switch hook
/ (Back Slash) Delays for 125 ms. before proceeding with dial string
W Waits for second dial tone (X2 or X4); linked to S6 register
@ (At Symbol) Dials, waits for quiet answer, and continues (X3 or higher)

$ (Dollar Sign) Displays a list of Dial commands

En Sets local echo
E0 Echo OFF
E1 Modem displays keyboard commands
Fn Sets online local echo of transmitted data ON/OFF
F0 Local echo ON; as the modem transmits data to a remote system, it also sends a copy of the data to the screen
F1 Local echo OFF; receiving system may send a remote echo of data it receives
Hn Controls ON/OFF hook
H0 Hangs up (goes on hook)
H1 Goes off hook

In Displays the following information:

I0 Four-digit product code
I1 Results of ROM checksum
I2 Results of RAM checksum
I3 Product type
I4 Current modem settings
I5 Stored memory settings
I6 Link diagnostics
I7 Product configuration
I9 Plug and Play information

I11 Extended link diagnostics

Ln Speaker Volume

L0 Lowest Speaker Volume
L1 LowSpeaker Volume
L2 Medium Speaker volume
L3 High Speaker Volume
Mn Operates speaker
M0 Speaker always OFF
M1 Speaker ON until CONNECT
M2 Speaker always ON
M3 Speaker ON after dial, until CONNECT
On Returns online
O0 Returns online
O1 Returns online and retrains
Qn Displays/suppresses result codes
Q0 Displays result codes
Q1 Quiet mode; no result codes
Q2 Displays result codes only in Originate mode

Sr.b=n Sets bit .b of register r to n (0/OFF or 1/ON)

Sr=n Sets register r to n

Sr? Displays contents of S-Register r

S$ Displays a list of the S-Registers

Vn Displays verbal/numeric result codes

V0 Numeric codes

V1 Verbal codes

XN Sets result code displayed, default is X4

Xn
Xn Setting
Result Codes
X0
X1
X2
X3
X4
0/OK
*
*
*
*
*
1/CONNECT
*
*
*
*
*
2/RING
*
*
*
*
*
3/NO CARRIER
*
*
*
*
*
4/ERROR
*
*
*
*
*
5/CONNECT 1200
 
*
*
*
*
6/NO DIAL TONE
 
 
 
*
*
7/BUSY
 
 
 
*
*
8/NO ANSWER
 
 
 
*
*
9/Reserved
 
*
*
*
*
10/CONNECT 2400
 
*
*
*
*
13/CONNECT 9600
 
*
*
*
*
18/CONNECT 4800
 
*
*
*
*
20/CONNECT 7200
 
*
*
*
*
21/CONNECT 12000
 
*
*
*
*
25/CONNECT 14400
 
*
*
*
*
43/CONNECT 16800
 
*
*
*
*
85/CONNECT 19200
 
*
*
*
*
91/CONNECT 21600
 
*
*
*
*
99/CONNECT 24000
 
*
*
*
*
103/CONNECT 26400
 
*
*
*
*
107/CONNECT 28800
 
*
*
*
*
151/CONNECT 31200
 
*
*
*
*
256/CONNECT 28000
 
*
*
*
*
260/CONNECT 29333
 
*
*
*
*
264/CONNECT 30666
 
*
*
*
*
268/CONNECT 32000
 
*
*
*
*
180/CONNECT 33333
 
*
*
*
*
272/CONNECT 34666
 
*
*
*
*
276/CONNECT 36000
 
*
*
*
*
280/CONNECT 38666
 
*
*
*
*
284/CONNECT 40000
 
*
*
*
*
188/CONNECT 41333
 
*
*
*
*
192/CONNECT 42666
 
*
*
*
*
196/CONNECT 44000
 
*
*
*
*
200/CONNECT 45333
 
*
*
*
*
204/CONNECT 46666
 
*
*
*
*
208/CONNECT 48000
 
*
*
*
*
212/CONNECT 49333
 
*
*
*
*
216/CONNECT 50666
 
*
*
*
*
220/CONNECT 52000
 
*
*
*
*
224/CONNECT 53333
 
*
*
*
*
228/CONNECT 54666
 
*
*
*
*
232/CONNECT 56000
 
*
*
*
*
Adaptive Dialling
 
 
*
*
*
Wait for 2nd Dial Tone (W)
 
 
*
 
*
Wait for Answer (@)
 
 
 
*
 
Fast Dial
 
 
*
 
*

*Requires @ in dial string; replaces NO CARRIER

Yn Selects power-on/reset default configuration

Y0 Use profile 0 setting in NVRAM
Y1 Use profile 1 setting in NVRAM
Y2 Use factory configuration 0 (&F0)
Y3 Use factory configuration 1 (&F1)
Y4 Use factory configuration 2 (&F2)

Z Resets modem

Z0 Resets modem to profile selected by Y command
Z1 Resets modem to profile 0
Z2 Resets modem to profile 1
Z3 Resets modem to factory default profile 0 (&F0)
Z4 Resets modem to factory default profile 1 (&F1)
Z5 Resets modem to factory default profile 2 (&F2)

Extended Data Commands

&$ Displays a list of ampersand (&) commands

&An Enables/disables additional result code subsets, see Xn

&A0 ARQ result codes disabled
&A1 ARQ result codes enabled
&A2 Modulation indicator added
&A3 Protocol indicators added*LAPM/MNP/NONE (error control) and V.42 bis/MNP5 (data compression)

&Bn Manages modem's serial port rate

&B0 Variable, follows connection rate
&B1 Fixed serial port rate
&B2 Fixed in ARQ mode, variable in non-ARQ mode

&Cn Controls Carrier Detect (CD) signal

&C0 CD override
&C1 Normal CD operations

&Dn Controls Data Terminal Ready (DTR) operations

&D0 DTR override
&D1 DTR toggle causes online Command mode
&D2 Normal DTR operations
&D3 Resets on receipt of DTR

&Fn Loads a read-only (non-programmable) factory configuration

&F0 Generic template; no flow control
&F1 Hardware flow control template
&F2 Software flow control template

&Gn Sets Guard Tone

&G0 No guard tone, U.S. and Canada
&G1 550 Hz guard tone, some European countries, requires B0 setting
&G2 1800 Hz guard tone, U.K., requires B0 setting

&Hn Sets Transmit Data (TD) flow control, see also &Rn

&H0 Flow control disabled
&H1 Hardware flow control, Clear to Send (CTS)
&H2 Software flow control, Xon/Xoff
&H3 Hardware and software flow control

&In Sets Receive Data (RD) software flow control, see also &Rn

&I0 Software flow control disabled
&I1 Xon/Xoff signals to your modem and remote system
&I2 Xon/Xoff signals to your modem only

&Kn Enables/disables data compression

&K0 Data compression disabled
&K1 Auto enable/disable
&K2 Data compression enabled
&K3 MNP5 compression disabled

&Mn Sets Error Control (ARQ) for connections at 1200 bps and higher

&M0 Normal mode, error control disabled
&M1 Reserved
&M2 Reserved
&M3 Reserved
&M4 Normal/ARQ
&M5 ARQ mode

&Nn Sets connect speed, if connection cannot be made at this speed, the modem will hang up. When used in conjunction with &Un and &Un is greater than 0, &Nn sets the ceiling connect speed. &Un sets the floor connect speed. (See also the table in the &Un section.)

Note: &N17 through &N39 apply only to V.90 products.

&N0 Connection speed is determined by the remote modem

&N1 300 bps
&N2 1200 bps
&N3 2400 bps
&N4 4800 bps
&N5 7200 bps
&N6 9600 bps
&N7 12,000 bps
&N8 14,400 bps
&N9 16,800 bps
&N10 19,200 bps
&N11 21,600 bps
&N12 24,000 bps
&N13 26,400 bps
&N14 28,800 bps
&N15 31,200 bps
&N16 33,600 bps
&N17 28,000 bps
&N18 29,333 bps
&N19 30,666 bps
&N20 32,000 bps
&N21 33,333 bps
&N22 34,666 bps
&N23 36,000 bps
&N24 37,333 bps
&N25 38,666 bps
&N26 40,000 bps
&N27 41,333 bps
&N28 42,666 bps
&N29 44,000 bps
&N30 45,333 bps
&N31 46,666 bps
&N32 48,000 bps
&N33 49,333 bps
&N34 50,666 bps
&N35 52,000 bps
&N36 53,333 bps
&N37 54,666 bps
&N38 56,000 bps

&Pn Sets pulse (rotary) dial make /break ratio

&P0 Pulse Dialling Disabled (Default for CTR/TBR-21)
&P1 Denmark, Germany, Austria, Finland, Switzerland, Netherlands, Italy, U.S., South Africa, Czech Republic
&P2 France, U.K., Belgium, Ireland, Spain, Portugal, Australia, Asia, Korea
&P3 Norway
&P4 New Zealand
&P5 Japan
&P6 Sweden
&P7 Not Utilised

&Rn Sets Receive Data (RD) hardware low control, Request to Send (RTS), see also &Hn

&R0 Reserved
&R1 Modem ignores RTS
&R2 Received Data to computer only on RTS

&Sn Controls Data Set Ready (DSR) operations

&S0 DSR override; always ON
&S1 Modem controls DSR

&Tn Begins test modes

&T0 Ends testing
&T1 Analogue Loopback
&T2 Reserved
&T3 Local Digital Loopback
&T4 Enables Remote Digital Loopback
&T5 Prohibits Remote Digital Loopback
&T6 Initiates Remote Digital Loopback
&T7 Remote Digital with self-test and error detector
&T8 Analogue Loopback with self-test and error detector

&Un When set above 0, the value chosen from the table sets the floor connect speed (the lowest acceptable connect speed). If a connection cannot be made at or above this speed, the modem will hang up. This command can also be used in conjunction with &Nn.

Note: &U17 through &U39 apply only to V.90 products.

 
&N=0
&N>0
&U=0
 Connects at best possible speed between your modem and the remote modem. Attempts a connection at the speed defined by &Nn.
Note: These factory default settings should be sufficient for most users.
&U>0
 Connects at any speed faster than the value &Un. Connects at any speed between &Nn and &Un.

&Un (continued) When set above 0, the value chosen from the table sets the floor connect speed (the lowest acceptable connect speed). If a connection cannot be made at or above this speed, the modem will hang up. This command can also be used in conjunction with &Nn.

&U0 No restrictions on the minimum speed for the connection

&U1 300 bps
&U2 1200 bps
&U3 2400 bps
&U4 4800 bps
&U5 7200 bps
&U6 9600 bps
&U7 12,000 bps
&U8 14,400 bps
&U9 16,800 bps
&U10 19,200 bps
&U11 21,600 bps
&U12 24,000 bps
&U13 26,400 bps
&U14 28,800 bps
&U15 31,200 bps
&U16 33,600 bps
&U17 28,000 bps
&U18 29,333 bps
&U19 30,666 bps
&U20 32,000 bps
&U21 33,333 bps
&U22 34,666 bps
&U23 36,000 bps
&U24 37,333 bps
&U25 38,666 bps
&U26 40,000 bps
&U27 41,333 bps
&U28 42,666 bps
&U29 44,000 bps
&U30 45,333 bps
&U31 46,666 bps
&U32 48,000 bps
&U33 49,333 bps
&U34 50,666 bps
&U35 52,000 bps
&U36 53,333 bps
&U37 54,666 bps
&U38 56,000 bps

&Wn Writes current configuration to NVRAM templates

&W0 Modifies the NVRAM 0 template (Y0)
&W1 Modifies the NVRAM 1 template (Y1)

&Yn Sets break handling

&Y0 Destructive, but does not send break
&Y1 Destructive, expedited
&Y2 Nondestructive, expedited
&Y3 Nondestructive, unexpedited

&Zn=s Writes phone number string s at position n (n = 0*3)

&Zn=L Writes last executed dial string at position n (n = 0*3)

&Zn? Displays the phone number stored at position n (n = 0*3)

&ZL? Displays the last executed dial string

#CID=n Controls Caller ID feature

#CID=0 Caller ID disabled
#CID=1 Caller ID enabled with formatted information
#CID=2 Caller ID enabled with unformatted information

+++ Escapes to online-command mode

S-Registers

To change a setting, use the ATSr=n command, where r is the register and n is a decimal value from 0 * 255 (unless otherwise indicated).

Register
Default
Function
S0
0
 Sets the number of rings on which to answer in Auto Answer Mode. When set to 0, Auto Answer is disabled.
S1
0
 Counts and stores the number of rings from an incoming call. S0 must be greater than 0.
S2
43
 Stores the ASCII decimal code for the escape code character.
Default character is +.
A value of 128 - 255 disables the escape code.
S3
13
 Stores the ASCII code for the Carriage Return character.
Valid range is 0 - 127.
S4
10
 Stores the ASCII decimal code for the Line Feed character.
Valid range is 0 - 127.
S5
8
 Stores the ASCII decimal code for the Backspace character .
A value of 128*255 disables the Backspace key's delete function.
S6
2
 Sets the number of seconds the modem waits before dialling.
If Xn is set to X2 or X4, this is the time-out length if there is not a dial tone.
S7
60
 Sets the number of seconds the modem waits for a carrier.
S8
2
 Sets the duration, in seconds, for the pause (,) option in the Dial command.
S9
6
 Sets the required duration, in tenths of a second, of the remote modem's carrier signal before recognition by the modem.
S10
14
 Sets the duration, in tenths of a second, that the modem waits to hang up after loss of carrier. This guard time allows the modem to distinguish between a line disturbance from a true disconnect (hang up) by the remote modem.
Note: If you set S10 = 255, the modem will not hang up when carrier is lost.
Dropping DTR hangs up the modem.
S11
72
 Sets the duration and spacing, in milliseconds, for tone dialling.
S12
50
 Sets the duration, in fiftieths of a second, of the guard time for the escape code sequence (+++).
S13
0
 Bit-mapped register. Select the bit(s) you want on and set S13 to the total of the values in the Value column.
For example: ATS13 = 17 enables bit 0 (value is 1) and bit 4 (value is 16).
Bit
Value
Result
0
1
Reset when DTR drops
1
2
Reset non-MNP transmit buffer from 1.5K to 128 bytes*
2
4
Set backspace key to delete
3
8
 On DTR signal, autodial the number stored at position 0
4
16
 At power on/reset, autodial the number stored at position 0
5
32
 Reserved
6
64
 Disable quick retrains
7
128
 Disconnect on escape code
*The 1.5K-byte non-ARQ buffer allows data transfer with Xmodem- and Ymodem- type file transfer protocols without using flow control. The 128-byte option lets remote users with slower modems keep data you are sending from scrolling off their screens. When remote users send your computer an Xoff (Ctrl-S) and you stop transmitting, the data in transit from your modem's buffer does not exceed the size of their screen. This is also very helpful in situations when a remote modem/printer application is losing characters.
S14
0
 Reserved
S15
0
 Bit-mapped register setup. To set the register, see instructions for S13.
Bit
Value
Result
0
1
Disable ARQ/MNP for V.22
1
2
 Disable ARQ/MNP for V.22 bis
2
4
 Disable ARQ/MNP V.32/V.32 bis
3
8
 Disable MNP handshake
4
16
 Disable MNP level 4
5
32
 Disable MNP level 3
6
64
 MNP incompatibility
7
128
 Disable V.42 operation
To disable V.42 detect phase, select the total of the values for bits 3 and 7. (S15=136{the sum of values 8 and 128})
S14
0
 Reserved
S16
0
 Reserved
S17
0
 Reserved
S18
0
 Test timer for &T loopback testing.
Sets the time in seconds of testing before the modem automatically times out and terminates the test.
When set to 0, the timer is disabled.
Valid range is 1-255.
S19
0

Sets the duration, in minutes, for the inactivity timer.
The timer activates when there is no data activity on the phone line; at time-out the modem hangs up.

S19=0 disables the timer.
S20
0
 Reserved
S21
10
 Sets the length, in 10-millisecond units, of breaks sent from the modem to the computer; applies to MNP or V.42 mode only.
S22
17
 Stores the ASCII decimal code for the Xon character.
S23
19
 Stores the ASCII decimal code for the Xoff character.
S24
0
 Reserved
S25
20
 Sets the duration, in hundredths of a second, that DTR must be dropped so that the modem does not interpret a random glitch as a DTR loss.
Most users will want to use the default.
This register is useful for setting compatibility with older systems running under older operating software.
S26
0
 Reserved
S27
0
 Bit-mapped register setup.
To set the register, see instructions for S13.
Bit
Value
Result
0
1
 Enables ITU-T V.21 modulation at 300 bps for UK calls
1
2
 Enables unencoded (non-trellis coded) modulation in V.32 mode
2
4
 Disables V.32 modulation
3
8
 Disables 2100 Hz answer tone to allow two V.42 modems to connect faster
4
16
 Enables V.23 fallback mode
5
32
 Disables V.32 bis mode
6
64
 Disable V.42 selective reject
7
128
 Software compatibility mode.
This setting disables the codes and displays the 9600 code instead.
The actual rate of the call can be viewed on the ATI6 screen.
Used for unusual software incompatibilities.
Some software may not accept 7200, 12,000, and 14,400 bps or greater result codes.
S28
0
 Eliminates the V.32 answer tones for a faster connection.
8 Default item, all times are in tenths of seconds.
255 Disables all connections except V.32 at 9600 bps.
S29
20
 Sets the duration, in tenths of a second, of the V.21 answer mode fallback timer.
S30
0
 Reserved
S31
128
 Reserved
S32
2
 Bit-mapped register setup.
To set the register, see the instructions for S13.
Bit
Value
Result
0
1
 V.8 Call Indicate enabled
1
2
 Enables V.8 mode
2
4
 Reserved
3
8
 Disable V.34 modulation
4
16
 Disable 33,600 bps and 31,200bps in V.34 modulation
5
32
 Disable 56K modulation
6
64
 Disable V.92 modulation.
7
128
 Disable V.92 modulation.
S33
0
 Bit-mapped register setup. To set the register, see the instructions for S13
Bit
Value
Result
0
1
 Disable 2400 symbol rate
1
2
 Disable 2743 symbol rate
2
4
 Disable 2800 symbol rate
3
8
 Disable 3000 symbol rate
4
16
 Disable 3200 symbol rate
5
32
 Disable 3429 symbol rate
6
64
 Reserved
7
128
 Disable shaping
S34
0
 Bit-mapped register setup. To set the register, see the instructions for S13.
Bit
Value
Result
0
1
 Disable 8S-2D trellis encoding
1
2
 Disable 16S-4D trellis encoding
2
4
 Disable 32S-2D trellis encoding
3
8
 Disable 64S-4D trellis encoding
4
16
 Disable non-linear coding
5
32
 Disable TX level deviation
6
64
 Disable Pre-emphasis
7
128
 Disable Pre-coding
S35-S37
 
 Reserved
S38
0
 Sets an optional delay, in seconds, before a forced hang-up and clearing of the Transmit buffer when DTR drops during an ARQ call. This allows time for a remote modem to acknowledge receipt of all transmitted data before it is disconnected. The modem immediately hangs up when DTR drops.
This option only applies to connections terminated by dropping DTR. If the modem receives the ATH command, it ignores S38 and immediately hangs up.
S39-S40
Reserved
S41
0
 Reserved
S42
0
 Reserved

Fax Commands

+FCLASS=n
 Sets the mode of operation
FCLASS=0
 Data Mode
FCLASS=1
 Group 3 Facsimile Service Class 1mode
FCLASS=2.0
 Group 3 Facsimile Service Class 2.0 mode
+FCLASS?
 Displays the current FCLASS mode. (See mode descriptions above)
+FCLASS=?
 Displays the FCLASS mode options (see mode descriptions above)
+FTS=n
 Stops the fax transmission
Then the modem waits for a specified time before OK appears on screen. The pause is set in 10 millisecond intervals. n is the number of 10 millisecond intervals that pass before OK appears. (n=0-255)
+FRS=n
 Makes the modem wait for a specified length of silence before sending OK to the screen
The pause is set in10 millisecond intervals. n is the number of 10 millisecond intervals that pass before OK appears. (n=0-255)
Note: This command terminates with OK when either the specified amount of silence is detected or when the user types anything (which is ignored).
+FTM=n
 Transmits data using the modulation specified by n (n = 3, 24, 48, 72, 96, 97, 98, 121, 122, 145, or 146) Note: See the "Screen Messages" table at the end of this section for an explanation of messages that appear in response to this command.
+FRM=n
 Receives data using the modulation specified by n (n = 3, 24, 48, 72, 96, 97, 98, 121, 122, 145, or 146) Note: See the "Screen Messages" table at the end of this section for an explanation of messages that appear in response to this command.
+FTH=n
 Transmits data framed in the HDLC protocol using the modulation specified by n
(n = 3, 24, 48, 72, 96, 97, 98, 121, 122, 145, or 146)
Note: See the "Screen Messages" table at the end of this section for an explanation of messages that appear in response to this command.
+FRH=n
Receives data framed in the HDLC protocol using the modulation specified by n (n = 3, 24, 48, 72, 96, 97, 98, 121, 122, 145, or 146)
Note: See the "Screen Messages" table at the end of this section for an explanation of messages that appear in response to this command.

Screen Messages

Numeric Message
Text Message
Description
0
OK
 The previous command has been processed successfully.
1
CONNECT
 The modem has just connected to another modem.
2
RING
 Reports the receipt of a network altering ring.
3
NO CARRIER
 No carrier is being received from the modem.
4
ERROR
 The previous command line has not been recognised or was completed abnormally.
5
NO DIAL TONE (OPTIONAL)
 Dial tone was not received within the time-out period.
6
BUSY (OPTIONAL)
 A busy signal was detected.
64
CONNECT/FAX (OPTIONAL)
 The modem has established a fax connection. This response is used only when the fax mode is selected

The Serial Interface

The serial interface is a standard developed by the Electronic Industries Association (EIA). It defines the signals and voltages used when data is exchanged between a computer and a modem or serial printer.

The entire standard covers many more functions than are used in most data communications applications. Data is transmitted between the devices over a shielded serial cable with a 25-pin male (DB-25) connector to the modem and a 25-pin, 9-pin, 8-pin, or custom-built connector to the computer.

The use of a shielded cable when connecting a modem to a computer is recommended to ensure minimal interference with radio and television.

Pin assignments are factory-set in the USRobotics modem to match the standard DB-25 assignments in the following table. DB-9 connectors for IBM/AT-compatible computers should be wired at the computer end of the cable as shown in the DB-9 column.

Serial Interface Pin Definitions

Signal Source

DB-25
DB-9
Circuit
Function
Computer/Modem
1
-
AA
 Chassis Ground Both
2
3
BA
 Transmitted Data Computer
3
2
BB
 Received Data Modem
4
7
CA
 Request to Send Computer
5
8
CB
 Clear to Send Modem
6
6
CC
 Data Set Ready Modem
7
5
AB
 Signal Ground Both
8
1
CF
 Carrier Detect Modem
12
-
SCF
 Speed Indicate Modem
20
4
CD
 Data Terminal Ready Computer
22
9
CE
 Ring Indicate Modem