9. Insert the strain relief assembly with the wire going through it
into the slot in the bottom half of the modem case and set it into the
recess in the case.
10. BEND the top half of the case as necessary to place it over
the strain relief assembly. Do not snap the case together yet.
11. Insert one captive screw through a saddle washer and then
insert the captive screw with the washer on it, through the hole in the
DB-25 end of the case. Snap that side of the case closed. Repeat the
process for the other side. This completes the cable installation
process.
4.1.4 2-WIRE CONNECTION
Most RS-485 devices employ a two-wire, half duplex configuration.
When using this configuration, be sure to first set the Model 285 to
"two wire" mode—then use
only the transmit (XMT) pair as shown
below:
285 SIGNAL
RS-485 SIGNAL
XMT+ ....................................+
XMT-.....................................-
The above wiring pattern applies regardless of whether you are
making the RS-485 connection via DB-25, RJ-11, RJ-45 or terminal
blocks. For specific wiring instructions, please refer to the previous
pages of Section 4.
4.2 CONNECTION TO THE RS-232 INTERFACE
Once you have properly configured the Model 285 and connected
the twisted pair wires correctly, all that remains is to plug the 285
directly into the DB-25 port of the RS-232 device. After doing so,
remember to insert and tighten the two captive connector screws.
(Note: If you must use a cable to connect the Model 285 to the RS-232
device, make sure it is a
straight through cable of the shortest possible
length—we recommend 6 feet or less).
4.3 OPERATING THE MODEL 285
Once the Model 285 is properly installed, it should operate trans-
parently—as if it were a standard cable connection. Operating power
is derived from the RS-232 data and control signals; there is no
"ON/OFF" switch. All data signals from the RS-232 and RS-485 inter-
faces are passed straight through. Additionally, one hardware flow
control signal is passed
in each direction.
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