Basic Hayes Modem (AT) Commands
Every modem that is called "Hayes compatible" follows a certain set of codes
which tell the modem what to do. In the case of some programs, you don't have
to know these commands to dial your modem, because the program does it for you.
On the other hand, other programs (such as KERMIT) require that you know these
commands to dial your modem and perform other useful functions. Here is a list
of commands you may find helpful:
- AT
- tells your modem that you are going to send it a command. You
must type "AT" before you issue any other command. If you issue AT as a
command all by itself, the modem should respond "OK". This indicates
that your cables are connected correctly and the baud rate is set properly.
- D
- tells your modem to dial the numbers following the "D."
- T
- is a subcommand of the "D" command. It tells your modem that you
want it to dial in touch-tone mode. Use this command only if you have a
touch-tone phone line.
- P
- is a subcommand of the "D" command. This tells your modem that you
want it to dial in pulse mode. Use this if you do not have a touch-tone
phone line.
Helpful Hints
- The order in which the commands are issued is important. "AT" must
always be the first command you type. Once you give the "D" command, any
character typed after it either is executed as a subcommand of the "D"
command or is dialed. Therefore, if you typed the "M0" command after the
"D" command, the modem would try to dial M0 instead of trying to shut off
the sound.
- Do not leave any spaces between any of the commands or the numbers
that you are dialing.
- If you are trying to use a modem you must turn off the "call-waiting"
feature on your phone when you dial the modem.
Disabling call-waiting is important
because if somebody does call you in the middle of a session, the
click made by the phone will disturb the transmission and cause garbage to
appear on your screen or in your file.
Examples of Commands
1) Dialing from an standard residence phone line:
- AT (Hit the return key) ...the modem responds "OK"
- ATDT250-727-3335 (Hit the return key) ...dialing from a touch-tone
- ATDP250-727-3335 (Hit return key) ....dialing from a pulse dial phone
What can go wrong:
The modem may not be working. To test the modem, give the command:
AT ..(in capital letters), then press the Return key. The modem should
reply: OK ..if you don't see an "OK" the modem isn't working. This could be
because you chose the wrong baud rate, or because the modem isn't connected to
the correct port, or because the modem isn't working. (Is it plugged in?)
If the modem isn't working, try to borrow a working modem and try again.
Follow this link to learn more about
modem commands and obtain a listing.
