ADTRAN Express 3000 SP, Руководство пользователя

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61203153L3-20 Express 3000 SP User Manual A-1
Appendix A
AT Commands and
S-Registers
AT COMMANDS
AT commands issue directions to the Express 3000 SP via a VT-100 ter-
minal emulation session. The DTE serial port accepts AT commands
only when no calls are established; i.e., the carrier detect (CD) signal is
inactive. When a call is established, the CD signal is active and the port
is used for data. The port cannot be used simultaneously to issue AT
commands and transmit and receive data. After entering command
mode (CD inactive), you can transmit AT commands to the Express
3000 SP to configure most options, dial remote Express 3000 SPs, and
initiate tests to check both the Express 3000 SP and the network con-
nections.
Escape Sequence and Guard Time Delay
To exit data mode (CD active) and enter command mode, the DTE se-
rial port must transmit a proper escape sequence to the Express 3000
SP. A specified time delay must occur between the last data character
and the first escape sequence character. This delay is the guard time
delay. You can change the guard time by writing a value to the S12
register. For a valid escape sequence to occur, the DTE must transmit
the escape code character three times in succession with the delay be-
tween each character less than the guard time.
The default escape sequence is
+++
and the default guard time delay
is one second.