14
ASYNC SHORT-HAUL MODEM MP
4.2.2 S
TAR
T
OPOLOGY
Using a star topology, you may connect several Modems together in a master/slave
arrangement. Maximum distance between the units will vary based upon the
number of drops, data rate, wire gauge, etc. Call Technical Support for specific
distance estimates.
Figure 4-3 shows how to wire the two-pair cables properly for a Modem star
topology. Note that the ground connection is not needed.
Figure 4-3. Modem star wiring.
HOST
FIRST SLAVE
SECOND SLAVE
XMT+
RCV+
RCV+
XMT-
RCV-
RCV-
RCV+
XMT+
XMT+
RCV-
XMT-
XMT-
In a multipoint topology, you must configure the master Modem’s DIP switches
differently than those of the slave Modems. Here are the proper DIP-switch settings
for a star topology:
Switch Number
1
2
3
4
5
6
7
Master Positions
ON
ON
ON
OFF
OFF
OFF
OFF
Slave Positions
ON
ON
ON
OFF
OFF
OFF
ON
4.3 RS-232 Connection
To connect the Modem to a piece of data terminal or data communications
hardware, use a straight-through RS-232 cable. Plug the cable directly into the
DB25 port on the rear of the Modem.
The DCE/DTE switches eliminate the need for a crossover cable.
