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Modem Configuration Examples 755
Restore the ex-factory modem settings
To restore the ex-factory modem settings, use the “AT&F” command.
[Router]script-string factory "" AT OK AT&F OK
[Router]interface serial 0
[Router-Serial0]start-chat factory
Configure the modem initialization parameters
Correctly initializing the modem configuration is an important step for the correct
connection with the modem. The following contents briefly introduce the
conventional AT initialization commands and the works for initialization.
■ When the negotiation is being carried out between modems, the modem
speed must not be changed. Otherwise, the user should send an AT command
to the remote modem so that the modem can be set to the new speed.
■ The port speed must not change when a session is negotiated with a remote
modem. If the speed of the port on the access server is changed, you must
establish a direct Telnet session to the modem and send an AT command so
that the modem can be set to the new speed.
■ Modems differ in the method they use to lock the EIA/TIA-232 serial interface
speed. Refer to the modem documentation to learn how the modem locks the
modem speed (check the settings &b, \j, &q, \n, or s-register settings).
■ The modem must use the data carrier detect (DCD) to indicate when a
connection is established with a remote end. Most modems use the &c1
command to implement the configuration. Refer to the modem
documentation for details.
■ The modem must disconnect the modem active connections via the data
terminal ready (DTR) signals. Most modems use &d2 or &d3 to implement the
setting. Refer to the modem documentation for details.
■ If the modem is required to access incoming calls, it must be configured with
the number of off-hook ringing for incoming calls. The user should not to
adopt the ringing auto-answer mode. S0=0 is adopted to make the
configuration for most of the modems. For details, please refer to the modem
operation manuals provided by the related manufacturers.
Considering the previously listed situations, the following initialization string is
designed for typical applications:
AT&b1&c1&d2&s0=0
The initialization string enables the following functions:
■ Locks the speed of the modem to the serial interface speed
■ Enables DCD
■ Enables disconnection of DTR
■ Configures the non-auto answer
[Router]script-string init "" AT&b1&c1&d2&s0=0 OK
[Router]interface serial 0
[Router-Serial0]start-chat init