28
SHORT-HAUL MODEM-B SYNC (SHM-B SYNC)
3. Are any of the cables too long? RS-232 cables
shouldn’t be longer than 50 ft. (15.2 m); see
Appendix A
for distance guidelines for the 4-wire
twisted-pair cable.
4. Check the pinning of your RS-232 cable and of
your device’s RS-232 port.
5. Do a loopback test (see
Section 6.1
). If local
loopback fails, the RS-232 cable is probably
miswired, broken, or defective. If local loopback
succeeds but remote loopback fails, the 4-wire
cable is probably broken or defective.
6. Test each SHM-B Sync’s RS-232 interface with a
breakout box. Pins 4, 5, 6, 8, and 20 all have to be
“high” (above +3V) in order to enable data
communication. In particular, if Pin 8 (Carrier
Detect) is low, the local SHM-B Sync is not
receiving a carrier signal from the remote unit.
Содержание ME801-C
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