Trouble Shooting; At Command Set Problems - ZyXEL Communications U-336R/RE User Manual

Trouble Shooting

Your modem is designed to provide years of ultra high speed
satisfaction. In the unlikely event you encounter problems using
your modem, the tips in this section will help you to identify and
resolve them. Most modem problems are a result of incorrect
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
2. Check to see that your modem's COM port is not already
126 Diagnostics & Troubleshooting
Resent Expiration
Protocol Error
Break Timeout
DTR Dropped
Carrier Lost 1 (No handshaking response)
Carrier Lost 2 (Remote hang-up, busy tone heard)
communications software is using the same COM port as your
modem.
assigned to another installed serial device, such as a mouse or
laser printer.