ATE1 : Modem command echo enable, it's not always required, but it's handy for debugging. Any typing on keyboard will be echoed back by the modem.

ATQ0 : Returns result codes, usually a factory default.

ATV1 : Returns result codes in words (English). For example if someone was dialing into your modem, the modem would echo the message "RING" "RING" etc, to your console, Until the modem software recognised the "RING" string and told the modem to answer, with an "ATA".

AT&C1 : Will cause the DCD signal (from modem to PC) to track the actual state of the modem's carrier. The carrier is a signal sent across the phone line for the duration of the call.

AT&D2 : Tell the modem to hangup on any state change of the DTR signal. DTR comes from the PC and goes to the modem. DTR is used by modem software to hangup a modem.

AT&K3 : Enable hardware flow control, CTS/RTS handshaking.
 

^{Special for USR courier/sportster onlY}

AT&R2 : Receive data flow control, use RTS.

AT&H1 : Transmit data flow control, use CTS.

AT&I0 : Disable software flow control.
 

_{Other usefull commands For most Hayes compatable and USR modems}

ATM0 : Disables modem speaker

ATM1 : Speaker is enabled until carrier is detected, factory default.

ATL0 : Sets volume of modem speaker level, 0 is lowest volume.

ATL3 : and 3 is the highest.

A/ : Repeats the last command entered.

AT&V : Displays the stored and active modem profile settings.

ATI4 : Display the stored and active modem profile settings.For USR courier/sportster

AT&W : Write current configuration into stored profile zero.

AT&F : Restore factory defaults.
 

^{Dialing information}

ATDT : To dial a number use the "ATDT" command. ExampleATDT { phone number }.
These are various dial modifiers

, : A comma is used to pause for a number of seconds.

W : Instructs the modem to wait for a dial tone, before dailing

9 : Also sometimes a prefix number is required to get out of PBX boxes. Example 9,w 1 519 836 5848

+++ : This is the Escape Code Sequence, The modem goes from online to command mode. Thats +++.

ATZ : Used in command mode, tells modem to hangup.

ATA : Answer line when "RING" "RING" is received on console.

_{Fax modems}

AT + FCLASS = ? : To determine the type of fax modem. Class1 or Class2 ?