U.S. Robotics 56K Corporate Modem
Commands
This card provides a quick reference for the most commonly used
AT commands. Defaults in bold type.
NOTE: Refer to the Alphabetic Command Summary, in the User
Guide on the CD-ROM for additional commands, like the Percent
(%) and Octothorpe (#) command sets.
Kn
BASIC COMMAND SET
Ln
Command/Description
$
+++
>
A
A/
A>
AT
Bn
Cn
Dn
En
Fn
Hn
In
Displays Help for the basic command set
Escape code
Repeat command (up to 10 attempts)
modem answers when there’s no incoming call
Reexecutes the last-issued command
Repeats the last issued command until canceled
Attention prefix
Sets handshaking options:
B0 ITU-T V.32 originate mode
B1 HST originate mode; Bell answer tone
Sets transmitter
B0 Transmitter off
B1 Transmitter on
Dials phone numbers and issues commands for
dialing options:
P Pulse dial
T Tone dial
,
(Comma) Pause for 2 seconds
;
(Semicolon) Return to command mode after
dialing
“ Dial the letters that follow
W Wait for a second dial tone (if X3 or higher)
@ Wait for an answer (with X3, X4 or X7)
/
Pause for 125 milliseconds
R Reverse frequencies
! Flash the switchhook
L? Display the last-dialed number
L Redial the last number
Sn Dial number stored in non-volatile random access
memory (NVRAM) at position n
$ Display Help for the dial commands
Command mode echo
EO Echo OFF; What you type will not display
E1 Echo On; What you type will display
Online local echo
F0 Echo ON
F1 Echo OFF
On/Off hook control
H0 Go on hook (hang up)
H1 Go off hook (pick up)
Queries the modem
I3 Banner
I4 Current settings
Mn
On
P
Qn
Sr=n
Sr.b=n
Sr?
S$
T
Vn
Xn
X3
X4
X7
Z
Z!
I5 NVRAM settings
I6 Statistics for preceding call
I7 Product configuration
I10 Dial security account status
I11 Extended Link Screen
I15 Caller ID information
Controls the modem clock
K0 If online, current call duration
K1 Displays real time
Controls speaker volume
L0 Low volume
L1 Low volume
L2 Medium volume
L3 High volume
Controls when the speaker sounds
M0 Always OFF
M1 ON until call is negotiated
M2 Always ON
M3 ON after last digit is dialed
Return online; use with escape code (+++)
O0 Return online
O1 Return online and retrain
Pulse dial
Enables or disables the display of result codes
Q0 Display
Q1 Suppress (quiet)
Q2 Suppress when answering
Sets S-register value; r is any S-Register; n must be
a decimal between 0 and 255
Sets bit-mapped register; r is the S-register, b is
the bit, and n is 0 (OFF) or 1 (ON)
Queries contents of S-register r
Displays s-register help
Tone dial
Displays result codes verbally or numerically
V0 Numeric
V1 Verbal
Call progress reporting
Ignore dial tone
Microsoft® default
Courier V.Everything Modem default
Software reset
Hardware reset
&Bn
&Cn
&Dn
&Fn
&Gn
&Hn
&In
&Kn
AMPERSAND (&) COMMAND SET
&Mn
Command/Description
&$
&An
Displays Help for the ampersand (&) command set
Enables or disables the additional result code subsets
&A0
Disables the display of additional result codes
&A1
Displays ARQ result codes
&A2
Displays ARQ result codes, modulation
indicators
&A3
Displays ARQ result codes, modulation
indicators, and error control indicator
Sets the serial port rate
&B0
Variable
&B1
Fixed
&B2
Fixed serial port rate in ARQ mode;
variable rate in non-ARQ mode
Controls Carrier Detect (CD)
&C0
CD always on
&C1
Normal CD operations
Controls Data Terminal Ready (DTR)
&D0
Ignore DTR
&D1
Online command mode with DTR toggle
&D2
Normal DTR operations
&D3
Modem resets with DTR toggle
Loads configuration template
&F0
Loads No flow control template
&F1
Loads Hardware flow control template
&F2
Loads Software flow control template
Sets guard tone
&G0
No guard tone (U.S., Canada)
&G1
Guard tone (Some European countries)
&G2
Guard tone (UK); requires ATB0
Transmit Data flow control
&H0
Disables Transmit Data flow control
&H1
Hardware Clear to Send (CTS) flow control
&H2
Software flow control (XON/XOFF)
&H3
Hardware and software flow control
Received Data software flow control
&I0
Disables XON/XOFF flow control
&I1
Modem acts on XON/XOFF commands and
passes them to the remote device
&I2
Modem acts on XON/XOFF commands and
removes commands from the data stream
(recommended for ARQ mode)
&I3
External: Hewlett Packard-Host mode
(ARQMode Only)
&I4
External:Hewlett Packard-Terminal mode
(ARQMode Only)
&I5
XON/XOFF in non ARQ Mode
Enables or disables data compression
&K0
Disable
&K1
Auto enable/disable
&K2
Enable
&K3
Selective compression (V.42 bis only)
Error control
&M0
Normal mode; no error control
&M4
Normal /ARQ mode
&M5
Asynchronous ARQ mode
&Nn
Sets fixed link speed
&Nn&Un Sets highest and lowest link speeds
n=0
Variable connection rate
n=1
300 bps
n = 21 33.3 Kbps
n=2
1200 bps
n = 22 34.6 Kbps
n=3
2400 bps
n = 23 36.0 Kbps
n=4
4800 bps
n = 24 37.3 Kbps
n=5
7200 bps
n = 25 38.6 Kbps
n=6
9600 bps
n = 26 40.0 Kbps
n=7
12.0 Kbps
n = 27 41.3 Kbps
n=8
14.4 Kbps
n = 28 42.6 Kbps
n=9
16.8 Kbps
n = 29 44.0 Kbps
n = 10
19.2 Kbps
n = 30 45.3 Kbps
n = 11
21.6 Kbps
n = 31 46.6 Kbps
n = 12
24.0 Kbps
n = 32 48.0 Kbps
n = 13
26.4 Kbps
n = 33 49.3 Kbps
n = 14
28.8 Kbps
n = 34 50.6 Kbps
n = 15
31.2 Kbps
n = 35 52.0 Kbps
n = 16
33.6 Kbps
n = 36 53.3 Kbps
n = 17
28.0 Kbps
n = 37 54.6 Kbps
n = 18
29.3 Kbps
n = 38 56.0 Kbps
n = 19
30.6 Kbps
n = 20
32.0 Kbps
&Rn
Received Data (RTS) hardware flow control
&R0
Delay clear to send (CTS) response
after RTS
&R1
Ignore RTS
&R2
Send data to the computer on receipt
of RTS
&Sn
Data Set Ready (DSR) signal from modem to pc
&S0
DSR always on
&S1
Originate mode: Send DSR after dialing
Answer mode: Send DSR after tone
&S2
Pulsed DSR with CTS following CD
&S3
Same as &S2, but without CTS
&S4
Simultaneous DSR with CD
&S5
Send DSR, and follow CTS with CD
&W
Writes the current settings to NVRAM
&Zn=s
Stores up to 10 phone numbers in NVRAM at
position n where n = 0-9
&Zn?
Displays the stored phone number
S-REGISTERS
Register Default Function
S0
S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
S11
S12
S13
S14
S15
S19
S21
S22
S23
S24
Sets the number of rings before Auto Answer
Counts and stores number of rings from calls
Stores code for the escape code character
Stores the code for the carriage return
Stores the code for the line feed character
Stores the code for the back space character
Stores the wait time for dial tone
Stores the wait time for carrier
Sets the comma time in seconds
Sets duration (1/10 of sec.) of remote
carrier signal before modem recognition
14 Sets duration (1/10 of sec.) modem waits
after loss of carrier before hanging up
70 Set touch tones spacing in 1/10 seconds.
50 Sets the guard time for the escape code
0
Bit-mapped register
Bit Value
Result
0
1
Reset when DTR drops
1
2
Originate mode in Auto Answer
2
4
Disables pause before result codes
3
8
Auto Dial the number stored in NVRAM
position 0 on DTR
4
16
At power on, Auto Dial number
stored in NVRAM at position 0
5
32
Disable HST
6
64
Disable MNP Level 3
7
128
Hardware Reset
1
Bit-mapped register
Bit Value
Result
0
1
Disconnects on Escape code
0
Bit-mapped register
Bit Value
Result
0
1
Disables high frequency
equalisation
1
2
Disables online fallback
2
4
Disables 450 bps back channel
3
8
Sets non-ARQ buffer to 128 bytes
4
16
Disables MNP Level 4
5
32
Set backspace key to delete
6
64
Unusual MNP incompatibility
7
128
Custom applications only
0
Sets the inactivity timeout, in minutes
10 Length of break in ARQ mode, 1/100 seconds
17 Stores the ASCII code for the XON character
19 Stores the ASCII code for the XOFF character
150 Sets DSR pulse time in 20-milliseconds
S25
S26
S27
0
0
43
13
10
8
2
60
2
6
S28
S29
S34
S38
S41
S42
S43
S44
S51
S53
S54
5
Sets DTR recognition in 10-milliseconds
1
Sets the RTS/CTS delay, 10-milliseconds
0
Bit-mapped register
Bit Value
Result
0
1
Enables V.21 modulation at 300 bps
1
2
Disables Trellis Code modulation
2
4
Disables V.32 modulation
3
8
Disables 2100 Hz answer tone
4
16
See Bit 4 and Bit 5 below
5
32
See Bit 4 and Bit 5 below
7
128
Unusual software compatibility
Bit4 Bit5
Result
0
0
Complete handshaking sequence
16 0
Disables MNP
0
32
Disables V.42 detection and LAPM
16 32
Disables detection phase
8
Sets duration, in tenths of a second, of extra
3000/600 Hz answer tones
20 Sets, in tenths of a sec, of the V.21answer tone
0
Bit-mapped register
Bit Value
Result
0
1
Disables V.32 bis
1
2
Disables enhanced V.32 Mode
2
4
Disables Quick V.32 Retrain
3
8
Enables V.23 modulations
4
16
Externals: Forces MR LED to show DSR
6
64
Disables remote access busy message
7
128
Disables V.32 terbo
0
Sets duration, in seconds, before a forced hang up
0
Sets number of attempts for remote access
126 Stores the ASCII code for remote access escape
200 Sets the guard time for the remote access
sequence, in 1/50th of a second
15 Leased line delay timer
0
Bit-mapped register
Bit Value
Result
0
1
Disables MNP/V.42 in V.22
1
2
Disables MNP/V.42 in V.22bis
2
4
Disables MNP/V.42 in V.32
6
64
Disables selective reject
0
Bit-mapped register
Bit Value
Result
0
1
Enables dial security
1
2
Enables prompting
2
4
Enables local password protection
64 Symbol bit-mapped register
Bit Value
Result
0
1
Disable 2400 symbol rate
1
2
Disable 2743 symbol rate
S55
S56
S58
S69
S70
2
3
4
5
6
7
0
Bit
0
1
2
3
7
0
Bit
0
1
2
3
4
5
6
7
0
Bit
0
5
0
Bit
0
1
0
Bit
0
1
2
3
4
Disable 2800 symbol rate
8
Disable 3000 symbol rate
16
Disable 3200 symbol rate
32
Disable 3429 symbol rate
64
Disable Call Indicate (CI)
128
Disable V.8
Trellis code bit-mapped register
Value
Result
1
Disable 8S-2D trellis code
2
Disable 16S-4D trellis code
4
Disable 32S-2D trellis code
8
Disable 64S-4D trellis code
128
Enable phase roll detection
Bit-mapped register
Value
Result
1
Disable non-linear coding
2
Disable TX level deviation
4
Disable preemphasis
8
Disable precoding
16
Disable shaping
32
Disable V.34+
64
Disable V.34
128
Disable V.FC
Bit-mapped register
Value
Result
1
Disables x2
32
Disables V.90
Bit-mapped register
Value
Result
1
Disables plug/play signalling
2
Enables carrier loss redial
Bit-mapped register
Value
Result
1
Enables recognition of Ring A
2
Enables recognition of Ring B
4
Enables recognition of Ring C
8
Enables recognition of Ring D
U.S. Robotics 56K Corporate
Modem
Quick Reference Card
Quick
Reference
Card
PN R24.0330.00
Copyright© 2002 U.S. Robotics Corporation. All rights reserved. U.S. Robotics and the U.S.
Robotics logo are registered trademarks of U.S. Robotics Corporation. Other product names
are for identification purposes only and may be trademarks of their respective companies.
Product specifications subject to change without notice.
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