Specifications

09/01/01 4:29 PM Diagnostics Tests 4-1
Chapter 4
Troubleshooting and
Diagnostics
4.1 Frequently Asked Question
Question: How can I connect six pairs of DTEs for transferring Data and
Control Signals (RTS to DCD) end-to-end?
Answer: First set the jumper marked “SELECT 6 OR 12 CHANNELS” to the
“12” position. Now FLM-1 passes 12 pairs of signals (TD and RD of channels
1 to 6 and secondary TD and RD of channels 7 to 12) end-to-end. All the
other channel signals are local: they do not pass end-to-end, being
transmitted between FLM-1 and the DTE (see Table B-2).
To transfer the control signals end-to-end, you must make a special cable. If
you have a model with DB-25 subchannel connectors, for exact wiring see
Figure 2-10; if your model has RJ-45 subchannel connectors, see
Figure 2-12. This way you are using channel 1 to pass the data signals
end to-end, and channel 7 (secondary channel) to pass the RTS and DCD
signals end-to-end.
4.2 Diagnostics Tests
FLM-1 features ITU V.54 diagnostic capabilities for performing loopback
tests. FLM-1 supports two types of loopback tests: a local loopback and
remote loopback.
Note
Before you start to perform any of the loopback tests, set to OFF (negative
voltage) the following signals at the remote unit subchannels:
- Received Data (Circuit 104)
- Clear to Send (Circuit 106)
- Receive Line Signal Detector (Circuit 109)