At Command Set Problems - ZyXEL Communications U-336S User Manual

cabling or settings within your communications or fax software.
This section provides a list of more common problems that you may
encounter, followed by likely solutions.

AT Command Set Problems

Problem
Your modem does not respond to AT commands.
Solutions
1. Make sure the DTR LED is ON. If it is OFF, make sure your
communications software is using the same COM port as your
modem.
2. Check to see that your modem's COM port is not already
assigned to another installed serial device, such as a mouse or
laser printer.
Problem
Your modem fails to execute AT commands.
Solutions
1. Make sure the DTR LED is ON. If it is OFF, make sure your
communications software is using the same COM port as your
modem.
2. You may have omitted the characters AT from the beginning of
the command line. These characters must appear at the
beginning of each command line.
3. You may have typed the commands when your modem was in
data state instead of the command state. To switch from data
state to command state, type the escape sequence code +++. To
return to the data state, type ATO and press Enter.
Problem
You typed an AT command, but did not receive an OK or 0 result
code.
Diagnostics & Troubleshooting 135