ARCHIVED: What AT commands can I use with a Hayes compatible modem?

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The following is a list of Hayes compatible AT commands and S registers:

Command Description
AT
Attention command; defines speed, precedes common line
A/
Re-executes last command line if modem hasn't made connection
A
Modem goes off-hook in answer mode
B0
Sets CCIT V.22 operation when at 1200bps
B1
Sets Bell 212A operation when at 1200bps
C0 Sets transmit carrier off
C1 Sets transmit carrier on
D
Dial number following D in command line
E0
Modem doesn't echo commands back to terminal
E1
Modem echoes commands back to terminal
F0 Sets modem to half duplex
F1 Sets modem to full duplex
H0 Modem goes on-hook (hangs up)
H1
Enables switchhook and auxiliary relay
I0
Displays product Identification Code
I1
Performs checksum on firmware ROM; displays value
I2
Performs checksum on firmware ROM; returns "Error" or "OK"
I3
Returns make, model, firmware of modem; e.g., "U.S. Robotics 56K FAX EXT V5.1.4"
L1 Speaker volume low
L2 Speaker volume medium
L3 Speaker volume high
M0 Speaker off
M1
Speaker on until carrier detected
M2 Speaker always on
M3
Speaker on until carrier detected except when dialing
O0 Return to online
O1 Return to online with retrain
P
Pulse (for rotary [dial] telephone service)
Q0 Modem returns result codes
Q1
Modem doesn't display result codes
Sr=n Set S register r to value n
Sr? Display S register contents
T
Tone (for touch-tone telephone service)
V0 Short numeric result codes
V1 Full result codes
X0 CONNECT; result codes enabled
X1
CONNECT BBBB; result codes enabled, blind dial, busy signal not detected
X2
Modem waits for dial tone before dialing, all CONNECT BBB result codes enabled, busy signal not detected
X3
Modem blind dials, all CONNECT BBBB results codes enabled, modem sends BUSY if busy signal detected
X4
Modem waits for dial tone before dialing, all CONNECT BBBB results codes enabled, modem sends BUSY if busy signal is detected
Y0
Long space disconnect disabled
Y1 Long space disconnect enabled
Z
Load stored profile configuration
&C0 DCD always ON
&C1
DCD ON if data carrier present
&D0 Modem ignores DTR
&D1
Modem assumes command state with ON-to-OFF transition on DTR
&D2
Modem hangs up, assumes command state, disables auto answer upon detecting ON-to-OFF transition on DTR
&D3
Modem assumes initialization state with ON-to-OFF transition to DTR
&F
Load factory profile configuration
&G0 No guard tone
&G1 550Hz guard tone
&G2 1800Hz guard tone
&L0 Selects dial-up line
&L1 Selects leased line
&P0
Pulse dial make/break ratio 39/61 (USA/Canada)
&P1
Pulse dial make/break ratio 33/67 (UK/HK)
&R0 CTS follows RTS
&R1
Modem ignores RTS; CTS always on
&S0 DSR always ON
&S1
DSR compatible with EIA RS-232C
&T0 Ends test in progress
&T1
Initiate Local Analog Loopback Test
&T2 RESERVED
&T3 Initiate Digital Loopback
&T4
Grants request from remote modem for Digital Loopback
&T5
Denies request from remote modem for Digital Loopback
&T6
Initiate Remote Digital Loopback Test
&T7
Initiate Remote Digital Loopback Test with Self Test
&T8
Initiate Local Analog Loopback Test with Self Test
&W
Write present profile configuration to nonvolatile RAM
&Z
Stores a phone number in nonvolatile RAM

S registers

Command Description Duration Default
S0 Ring to answer 0-255 rings 0
S1 Number of rings 0-255 rings 0
S2 Escape character 0-127 ASCII 43(+)
S3 Carriage Return 0-127 ASCII 13(CR)
S4 Line Feed 0-127 ASCII 10(LF)
S5 Back Space 0-127 ASCII 8(BS)
S6 Wait for dial tone 2-255 seconds 2
S7 Wait for carrier 1-255 seconds 30
S8 Comma pause time 0-255 seconds 2
S9 Carrier response 1-255 .1 seconds 6
S10 Carrier loss delay 1-255 .1 seconds 7
S11 Tone duration 50-255 mseconds 70
S12 Escape guard time 20-255 .02 seconds 50
S13
Bitmapped UART status register
S14 Bitmapped Option register
S15 Bitmapped Flag register
S16 Bitmapped Test options
S17 RESERVED
S18 Test times 1-255 seconds 0
S19 RESERVED
S20 RESERVED
S21 Bitmapped
S22 Bitmapped
S23 Bitmapped
S24 RESERVED
S25 Delay to DTR 0-255 .01 seconds 5
S26 RTS to CTS delay 0-255 .01 seconds 1

This is document aaqc in the Knowledge Base.
Last modified on 2018-01-18 09:01:15.