13
CHAPTER 4: Operation
characters appear, check the 4 wire connections
between the two High Speed SHM-B Async units for
improper polarity or broken wires. See Figure 3 for
an illustration of the loopback mode.
When the loopback tests are completed, return both
High Speed SHM-B Async units to normal mode.
Data transmission between the two modems should
now be possible.
If you have problems communicating between the two
High Speed SHM-B Async units, refer to
Chapter 6
to
help diagnose the problem.
Figure 3. Activating the LOOPBACK switch.
TD
(RS-232)
RD
TX-
RX-
TX+
RX+
RD
(RS-232)
TD
RX-
TX-
RX+
TX+
TD
(RS-232)
RD
TX-
RX-
TX+
RX+
RX-
TX-
RX+
TX+
TD
(RS-232)
RD
TX-
RX-
TX+
RX+
TD
(RS-232)
RD
TX-
RX-
TX+
RX+
RD
(RS-232)
TD
SHM #1 in NORMAL mode.
SHM #2 in NORMAL mode.
SHM #1 in LOOPBACK mode.
SHM #2 in NORMAL mode.