Diagnostics and Trouble Shooting
Dialup / Leased Line Modem
20
Diagnostics and Trouble Shooting
Indicator Lights
Eight indicator lights are included on the front of a DLM to aid in troubleshooting your DLM
installation.
Light Description
CD
Indicates the DLM is connected to a remote modem
CTS
Indicates the DLM is ready to receive data or commands. On unless
hardware handshaking is enabled. If hardware handshaking is enabled
then light will flash off when the internal buffer of the DLM is full.
RTS
Indicates the status of the RTS line. When hardware handshaking is
enabled RTS indicates the DLM should stop sending data. Will be off if
3 wire RS232 used.
DTR
Indicates the status of the DTR line. DTR is used to disconnect a
connection when in either a Dial-Up or Leased-Line operation. Will be
off if 3 wire RS232 used.
DSR
Indicates the DLM is ready to receive commands. Always on.
RI
Ring Indicator. Indicates the phone line is ringing when connected to a
Dial-Up phone line. Light will remain off for a Leased-Line connection.
TX
Flashes when characters are transmitted to the Modem / Phone line.
RX
Flashes when characters are received from the Modem / Phone line.
Troubleshooting Hints
Loss of Connection / Failure to Connect
Due to conditions beyond the control of the DLM, the DLM may occasionally
either disconnect or fail to make a connection when used with either Dial-Up or
Leased-Lines. Any system design using a DLM or any other modem must be
able to detect an occasional communications fault and be configured to
automatically recover.
When the DLM is used with Dial-Up phone lines the master device initiating the
dialing should monitor carrier detect for a communications failure and attempt
redialing the phone number when a connection is broken.
When the DLM is used with Leased-Lines and the DLM was set up according
to this documentation the DLM will immediately attempt to reconnect on loss of
carrier.
While an occasional dropped or failed connection can not be prevented,
complete failure to connect or frequent dropped or failed connections indicate a
possible settings problem with your DLM and some settings may need to be
modified to produce more reliable communications.
