After you make a reverse Telnet connection to the modem, you need to test the connection. Send the modem the AT command to request its attention. It should respond with OK. For example:
at
OK
If the modem does not reply to the AT command, check the following:
Look at the output of the show line 1 command. If it displays "no CTS" for the modem hardware state, the modem is not connected or powered on, and is waiting for data; or the modem might not be configured for hardware flow control.
Check your cabling and the modem configuration (echo or result codes might be off). Enter the appropriate AT modem command to view the modem configuration, or enter the command at&f to return to factory defaults. Refer to your modem documentation to learn the appropriate AT command to view your modem configuration