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SHM-B ASYNC
When in loopback mode, the switch button indicator
will appear to the sender. If a CRT terminal is connected
to the SHM-B, typing characters on the keyboard should
result in the same characters appearing on the CRT
screen. If no characters appear, check your EIA-232
connections and the setting of S1. See Figure 3 for an
illustration of the loopback mode.
The TD and RD LEDs on the front panel of your SHM-B
indicate the status of the SHM-B transmitter and
receiver, respectively. Green indicates a LOW EIA-232
level and red indicates a HIGH EIA-232 level. The LEDs
will modulate as data is transmitted and received by the
SHM-B. Remember that these LEDs are monitoring the
actual received and transmitted signals, not the TD and
RD lines of the EIA-232 interface.
When the loopback test is completed, press the
LOOPBACK switch again to return the SHM-B to
normal mode. The switch button indicator should now
be black. Data transmission between the two modems
will now be possible.
If you experience problems communicating between the
two SHM-Bs, use Table 1 to help diagnose the problem.