
18
AT [CR]
([CR] represents a carriage return.)
If the modem responds with
OK
, it means that the modem has received and understood the
command. You are in terminal mode and ready to issue AT commands. If you are not in terminal
mode, refer to your software manual to determine how to get there.
C
OMMAND
S
TATE
AND
O
NLINE
S
TATE
The modem operates in either command or online state:
•
When you first turn your computer on, the modem is in command state. It must be in
command state to receive AT commands.
•
When your modem connects to another modem, it automatically changes to the online state.
Your modem must be in the online state for data to be transmitted.
If you’re connected to a network, Bulletin Board System or other remote computer (i.e., you’re
online) you can transmit data, but you must change to command state to send AT commands.
To change from one state to the other, use one of the following methods.
•
To change from online to command state, type the escape code (
+++
) as explained in the
next section.
•
To change from command state to online state, issue the command
ATO
(go back on-line),
ATA
(answer a call), or
ATD
(dial a number). Command Line Syntax is discussed in this
chapter. The AT commands are listed in Appendix B.
E
SCAPE
C
ODE
The escape code may be used while you are online to force the modem to the command state
without hanging up.
The escape code is a string of three ASCII plus signs (
+++
) preceded and followed by a one-second
“guard time” during which your hands must be off the keyboard. Do not transmit data for at least
one second. To issue the escape code when online, do the following:
1
Hands off keyboard. Do not transmit any data for a period equal to the guard time. (The
default setting for the guard time is one second.)
2
Type
+++
quickly. DO NOT press Carriage Return[CR] or Enter when you finish.
3
Hands off again. Do not transmit any data for another period of time equal to the guard time.
The modem responds to these steps with
OK
(or Ø if in numeric result code mode). If it doesn’t,
either it received data during the guard time or the escape code was typed too slowly. The time
between each plus sign (“+”) in the escape code should not exceed the guard time.