Hayes Modem Commands

The majority of modem manufactures have adhered, at least loosely, to the Hayes Command Set.

You can use the modem initialisation string to send set of commands to the modem to set such features as dialling mode, waits, detection of the busy signal etc.

Basic Command Set

Command	Parameter	Description
AT$		Basic command set help
A/		Repeat last executed command
AT		Required command mode prefix
A		Answer Call
Bn	n=0	V32 Mode/CCITT ans Seq
	n=1	Bell Answer Seq
	n=2	Verbose/Quiet On Answer
Dn		Dial a Telephone Number
DL		Dial Last Phone Number
DSn		Dial Stored Phone Number
D$		Dial commands set help
En	n=0	No Command Echo
	n=1	Echo Command Chars
Fn	n=0	Online Echo
	n=1	No Online Echo
Hn	n=0	On Hook (Hang Up)
	n=1	Off Hook
In	n=0	Product Code
	n=1	Checksum
	n=2	RAM Test
	n=4	Current Settings
	n=5	NVRAM Settings
	n=6	Link Diagnostics
	n=7	Product Configuration
Ln	n=0	Low Speaker Volume
	n=1	Low Speaker Volume
	n=2	Med Speaker Volume
	n=3	Hi Speaker Volume
Mn	n=0	Speaker Off
	n=1	Speaker OnUntil CD
	n=2	Speaker Always On
	n=3	Speaker Off During Dial
On	n=0	Return Online
	n=1	Return Online & Retrain
P		Pulse Dial
Qn	n=0	Result Codes Sent
	n=1	Quiet (No Result Codes)
Sr=n		Sets Register “r” to “n”
Sr?		Query Register “r”
S$		S Registers command set help
T		Tone Dial
Vn	n=0	Numeric Responses
	n=1	Verbal Responses
Xn	n=0	Basic Result Codes
	n=1	Exended Result Codes
	n=2-4	Advanced Result Codes
Yn		Select power on/reset default configuration
	n=0	Next reset to &W0 settings
	n=1	Next reset to &W1 settings
Zn		Reset modem based on current DIP switch settings
	n=0	Dipswitch #7 determines reset
	n=1	Reset to &W0 settings
	n=2	Reset to &W1 settings
	n=3	Reset to &F0 settings
	n=4	Reset to &1 settings
	n=5	Reset to &F2 settings
+++		Escape Code

Extended Command Set

Command	Parameter	Description
AT&$		Extended command set help
&An	n=0	Disable /ARQ Result Codes
	n=1	Enable /ARQ Result Codes
	n=2	Enable /Modulation Codes
	n=3	Enable /Extra Result Codes
&Bn	n=0	Floating DTE Speed
	n=1	Fixed DTE Speed
	n=2	DTE Speed Fixed When ARQ
&Cn	n=0	CD Always On
	n=1	Modem Controls CD
&Dn	n=0	Ignore DTR
	n=1	On-Line Command Mode
	n=2	DTE Controls DTR
&Fn	n=0	Load Factory 0, no FC
	n=1	Load Factory 1, HW FC
	n=2	Load Factory 2, SW FC
&Gn	n=0	No Guard Tone
	n=1	550 Hz Guard Tone
	n=2	1800 Hz Guard Tone
&Hn	n=0	Disable TX Flow Control
	n=1	CTS
	n=2	Xon/Xoff
	n=3	CTS and Xon/Xoff
&In	n=0	Disable RX Flow Control
	n=1	Xon/Xoff
	n=2	Xon/Xoff Chars Filtered
	n=3	HP Enq/Ack Host Mode
	n=4	HP Enq/Ack Terminal Mode
	n=5	Xon/Xoff for non-ARQ Mode
&Kn	n=0	Disable Data Compression
	n=1	Auto Data Compression
	n=2	Enable Data Compression
	n=3	Selective Data Compression
&Mn	n=0	Normal Mode
	n=4	ARQ/Normal Mode
	n=5	ARQ Mode
&Nn	n=0	Highest Link Speed
	n=1	300 bps
	n=2	1200 bps
	n=3	2400 bps
	n=4	4800 bps
	n=5	7200 bps
	n=6	9600 bps
	n=7	12000 bps
	n=8	14400 bps
&Pn	n=0	N.American Pulse Dial
	n=1	UK Pulse Dial
&Rn	n=1	Ignore RTS
	n=2	RX to DTE/RTS high
&Sn	n=0	DSR Always On
	n=1	Modem Controls DSR
&Tn	n=0	End Test
	n=1	Analog Loopback (ALB)
	n=3	Digital Loopback (DLB)
	n=4	Grant Remote DLB
	n=5	Deny Remote DLB
	n=6	Remote Digital Loopback
	n=7	Remote DLBWith Self Test
	n=8	ALB With Self Test
&Wn	n=0	Store Configuration 0
	n=1	Store Configuration 1
&Yn	n=0	Destructive
	n=1	Destructive/Expedited
	n=2	Nondest./Expedited
	n=3	Nondest./Unexpedited
&Zn=s		Store Phone Number
&Zn?		Query Phone Number