User Manual

Modems Troubleshooting
9-16
9.8 Troubleshooting
To help diagnose any difficulty with your modem setup, it is a good idea to do the following:
◆ Install a breakout box between the modem and the SCS. Set all modem switches to the “normal”
position, and remove all jumpers. When the modem and SCS are powered on, the box’s LEDs will
display the state of the signals, enabling you to more easily diagnose the problem.
◆ Enable event logging for modems. Event Logging is discussed on page 11-24.
◆ Use the List Port command to ensure that modem control is enabled on the port. Many of the port’s
characteristics will be displayed; modem control is the third item listed in the left column.
◆ Ensure that all modems have been reset by rebooting the SCS.
◆ Verify the cable connections.
The following table lists some common problems that occur with modem configuration and proposes
solutions for them.
Table 9-3: Modem Troubleshooting
Problem Possible Cause(s) Remedy
The modem won’t
answer the phone.
The modem isn’t configured to
answer the phone.
Enable answering with the Define Ports Modem
Answer command (discussed on page 12-92).
The DTR signal isn’t attached. Verify the wiring. Ensure that the ground pins on the
RJ45 ports are wired together.
The SCS isn’t asserting the DTR
signal.
Ensure that the Dtrwait characteristic (discussed on
page 12-63) is disabled on the SCS port used.
The modem has hung. Cycle power on the modem.
The modem doesn’t
respond to the SCS’s
configuration requests.
The modem’s flow control isn’t set
properly, or the modem’s autobaud
isn’t functioning properly.
Reset the modem’s NVR to the factory default state
(the at&f string is commonly used). For further
instructions, refer to your modem’s documentation.
The modem isn’t wired correctly. Verify the wiring. Ensure that the ground pins on
RJ45 ports are wired together.
The modem answers,
but cannot connect to
the SCS.
The Access characteristic on the
SCS port is set to None or Remote.
Set Access (discussed on page 12-50) to Local or
Dynamic.
The modem’s serial speed does not
match the serial speed on the SCS
port used.
Ensure that the serial speeds of the modem and SCS
port match.
A network user is connected to the
modem.
Use the Show Ports command (discussed on page
12-88) to verify that the SCS port is idle. If it is not
idle, log out the port using the Logout Port Port
command (discussed on page 12-47).
The modem has hung. Cycle power on the modem.
The SCS cannot detect the DCD
signal.
Verify the wiring. Ensure that the ground pins on the
RJ45 ports are wired together.