Troubleshooting - Lantronix SCS Reference Manual

Modems

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 11-25.
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.
Problem
The modem won't
answer the phone.
The modem doesn't
respond to the SCS's
configuration requests.
The modem answers,
but cannot connect to
the SCS.
Table 9-3: Modem Troubleshooting
Possible Cause(s)
The modem isn't configured to
answer the phone.
The DTR signal isn't attached.
The SCS isn't asserting the DTR
signal.
The modem has hung.
The modem's flow control isn't set
properly, or the modem's autobaud
isn't functioning properly.
The modem isn't wired correctly.
The Access characteristic on the
SCS port is set to None or Remote.
The modem's serial speed does not
match the serial speed on the SCS
port used.
A network user is connected to the
modem.
The modem has hung.
The SCS cannot detect the DCD
signal.
Remedy
Enable answering with the Define Ports Modem
Answer command (discussed on page 12-3).
Verify the wiring. Ensure that the ground pins on the
RJ45 ports are wired together.
Ensure that the Dtrwait characteristic (discussed on
page 12-71) is disabled on the SCS port used.
Cycle power on the modem.
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.
Verify the wiring. Ensure that the ground pins on
RJ45 ports are wired together.
Set Access (discussed on page 12-57) to Local or
Dynamic.
Ensure that the serial speeds of the modem and SCS
port match.
Use the Show Ports command (discussed on page
12-96) 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 12-53).
Cycle power on the modem.
Verify the wiring. Ensure that the ground pins on the
RJ45 ports are wired together.
9-16
Troubleshooting