Modem operation is controlled by generic AT commands. These AT 
commands may be basic AT (i.e., commands preceded by AT, AT&, AT%), 
or S register (e.g., S6=n). 

Under the AT command set (with the exception of the A/ command), each 
command line must begin with the character sequence AT. Commands entered in 
upper case or lower case are accepted, but both the A and T must be 
of the same case. 

The AT sequence may be followed by any number of commands in 
sequence, except for commands such as Z, D, or A. Commands following 
commands Z, D, or A on the same command line will be ignored. The 
maximum number of characters on any command line is 256 (including 
"A" and "T").

Below is a pertial list of AT commands and S registers. 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

A/ - Re-execute Command

A - Answer the phone.

Dn - Dial
	This command directs the modem to go on-line, dial according to the 
	string entered and attempt to establish a connection. 
	Punctuation characters may be used for clarity, with parentheses, 
	hyphen, and spaces being ignored.
0-9	DTMF digits 0 to 9.
*	The 'star' digit (tone dialling only).
#	The 'gate' digit (tone dialling only).

P	Select pulse dialling
T	Select tone dialling
R	This command will be accepted, but not acted on.
!	Hook-Flash 
W	Wait for dial tone: the modem will wait for dial tone before 
	dialling the digits following "W". 
@	Wait for silence: the modem will wait for at least 5 seconds  
	before continuing with the next dial string parameter.
,	Dial pause
;	Return to command state.
^	Disable calling tone: applicable to current dial attempt only.
( )	Ignored: may be used to format the dial string.
-	Ignored: may be used to format the dial string.
<space>	Ignored: may be used to format the dial string.
<i>	Invalid character: will be ignored.
>	If enabled by country specific parameter, the modem will generate a 
	grounding pulse on the EARTH relay output.


En - Command Echo

E0	Disables command echo.
E1	Enables command echo. 

Hn - Disconnect (Hang-Up)

H0	The modem will release the line if the modem is currently on-line.
H1	If on-hook, the modem will go off-hook and enter command mode. 

In - Identification

I0	Reports product code .
I1	Reports pre-computed checksum from ROM.
I2	Computes checksum and compares it with value stored in ROM. 
I3	Reports firmware revision model code 
I4	Reports OEM defined identifier string 
I5	Reports Country Code parameter .

Ln - Speaker Volume

L0	Low volume.
L1	Low volume. 
L2	Medium volume.
L3	High volume.

Mn - Speaker Control

M0	Speaker is always off.
M1	Speaker is on during call establishment, but off when receiving 
	carrier. 
M2	Speaker is always on.
M3	Speaker is off when receiving carrier and during dialling, but on 
	during answering.

On - Return to On-Line Data Mode

O0	Enters on-line data mode without a retrain. 
O1	Enters on-line data mode with a retrain before returning to 
	on-line data mode.

P - Set Pulse Dial Default

Qn - Quiet Results Codes Control

Q0	Enables result codes to the DTE. 
Q1	Disables result codes to the DTE.

T - Set Tone Dial Default

Vn - Result Code Form

V0	Enables short-form (terse) result codes. Line feed is not issued 
	before a short-form result code.
V1	Enables long-form (verbose) result codes.


Zn - Soft Reset and Restore Profile

Z0	Soft reset and restore stored profile 0.
Z1	Soft reset and restore stored profile 1.

&Cn - RLSD (DCD) Option

&C0	RLSD remains ON at all times.
&C1	RLSD follows the state of the carrier.

&Dn - DTR Option

&D0 -	DTR drop is interpreted according to the current &Q setting as 
	follows:
	&Q0, &Q5, &Q6	DTR is ignored (assumed ON). Allows operation with 
	DTEs which don't provide DTR.
	&Q1, &Q4	DTR drop causes the modem to hang up. Auto-answer 
	is not affected.
	&Q2, &Q3	DTR drop causes the modem to hang up. Auto-answer is 
	inhibited.
&D1	DTR drop is interpreted according to the current &Q setting as 
	follows:
	&Q0, &Q1, &Q4, &Q5, &Q6	DTR drop is interpreted by the modem as if 
	the asynchronous escape sequence had been entered. The modem returns 
	to asynchronous command state without disconnecting.
	&Q2, &Q3	DTR drop causes the modem to hang up. Auto-answer is 
	inhibited.
&D2	DTR drop is interpreted according to the current &Q setting as 
	follows:
	&Q0 through &Q6	DTR drop causes the modem to hang up. Auto-answer is 
	inhibited.
&D3	DTR drop is interpreted according to the current &Q setting as 
	follows:
	&Q0, &Q1, &Q4, &Q5, &Q6	DTR drop causes the modem to perform a soft 
	reset as if the Z command were received. The &Y setting determines 
	which profile is loaded.
	&Q2, &Q3	DTR drop causes the modem to hang up. Auto-answer is 
	inhibited.

&F - Restore Factory Configuration 

&Gn - Select Guard Tone

&G0	Disables guard tone. 
&G1	Disables guard tone.
&G2	Selects 1800 Hz guard tone. 

&Kn - Flow Control

&K0	Disables flow control.
&K3	Enables RTS/CTS flow control. (Default for data modem modes.)
&K4	Enables XON/XOFF flow control.

&Ln - Leased Line Operation

&L0	Selects dial-up line operation. 
&L1	Selects leased line operation.
 
&Mn - Asynchronous/Synchronous Mode Selection

&M0	Selects direct asynchronous operation. 
&M1	Selects synchronous connect mode with async off-line command mode. 
&M2	Selects synchronous connect mode with async off-line command mode. 
&M3	Selects synchronous connect mode. 

&Pn - Select Pulse Dial Make/Break Ratio

&P0	Selects 39%-61% make/break ratio at 10 pulses per second. 
&P1	Selects 33%-67% make/break ratio at 10 pulses per second.
&P2	Selects 39%-61% make/break ratio at 20 pulses per second.
&P3	Selects 33%-67% make/break ratio at 20 pulses per second.

&Qn - Sync/Async Mode

&Q0	Selects direct asynchronous operation. See &M0.
&Q1	Selects synchronous connect mode with async off-line command mode.
&Q2	Selects synchronous connect mode with async off-line command mode.
&Q4	Selects AutoSync operation. 
&Q6	Selects asynchronous operation in normal mode. 

&Rn - RTS/CTS Option

&R0	In sync mode, CTS tracks the state of RTS.
&R1	In sync mode, CTS is always ON . 

&Sn - DSR Override

&S0	DSR will remain ON at all times.
&S1	DSR will become active after answer tone has been detected and 
	inactive after the carrier has been lost.

&V - Display Current Configuration and Stored Profiles.

&Wn - Store Current Configuration

&W0	Store the current configuration as profile 0.
&W1	Store the current configuration as profile 1.

&Yn - Designate a Default Reset Profile

&Y0	The modem will use profile 0.
&Y1	The modem will use profile 1.

\Nn - Operating Mode

\N0	Selects normal speed buffered mode.
\N1	Serial interface selected
\N2	Selects reliable (error-correction) mode. 
\N3	Selects auto reliable mode.
\N4	Selects LAPM error-correction mode. 
\N5	Selects MNP error-correction mode.

%C - Enable/Disable Data Compression

%C0	Disables data compression. 
%C1	Enables MNP 5 data compression negotiation. 
%C2	Enables V.42 bis data compression.
%C3	Enables both V.42 bis and MNP 5 data compression. 

S0 - Number of Rings to Auto-Answer
S1 - Ring Counter
S2 - Escape Character
S3 - Carriage Return Character
S4 - Line Feed Character
S5 - Backspace Character
S6 - Wait Time for Dial Tone Before Blind Dialing.
S7 - Wait Time For Carrier After Dial
S8 - Pause Time For Dial Delay
S9 - Carrier Detect Response Time
S10 - Lost Carrier To Hang Up Delay
S11 - DTMF Tone Duration
S12 - Escape Code Guard Time
S13 - Reserved
S14 - General Bit Mapped Options
S15 - Reserved
S16 - General Bit Mapped Test Options
S17 - Reserved
S18 - Test Timer
S19 - AutoSync Registers
S21 - V.21/General Bit Mapped Options
S22 - Speaker/Results Bit Mapped Options
S23 - General Bit Mapped Options
S24 - Sleep Inactivity Timer
S25 - Delay To DTR
S26 - RTS to CTS Delay 
S27 - Bit Mapped Option
S28 - Bit Mapped Options
S29 - Flash Dial Modifier Time
S30 - Disconnect Inactivity Timer
S31 - Bit Mapped Options
S32 - XON Character
S33 - XOFF Character
S34-S35 - Reserved
S36 - LAPM Failure Control 
S37 - Desired Line Connection Speed
S38 - Delay Before Forced Hang Up
S39 - Flow Control
S40 - General Bit Mapped Options
S41 - General Bit Mapped Options
S46 - Data Compression Control
S46=136	Execute error correction protocol with no compression.
S46=138	Execute error correction protocol with compression. 
S48 - V.42 Negotiation Action
