SHM-B Async

printed circuit board is properly inserted and fully seated against the motherboard of the rack.

SYMPTOM: No data transfer in one or both directions (to, from, or to-and-from the SHM-B).

1.Monitor the TD LED on the sending-end modem while sending data. The light should flash red/green. If not, check the DCE/DTE switch on that unit. Once you get a TD LED flashing on that unit, simultaneously the RD LED should flash on the other SHM-B unit. If not, go to step 2.

2.Inspect the wiring between the two modems. Have the wires been properly installed? Transmit + (TX+) on one modem must be wired to Receive + (RX+) on the other modem; also, Transmit - (TX-) must be wired to Receive - (RX-). Refer to Figure 2 during your inspection of the four-wire circuit.

3.Try a local test using the Loopback mode (see Chapter 4). If there is no transfer, check the setting of S1 and the wiring of your EIA-232 cable.

4.The EIA-232 control signals are at the wrong levels. Check the EIA-232 interface using a breakout box.