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Page 18
Black Box Short Range Modem
to avoid ground loops. A ground wire is not necessary for proper operation of
these units.
5. When you finish connecting the telephone line to units at both ends, it should
look like the following diagram:
3.3 FOUR-WIRE, MULTIPOINT INSTALLATION
Multipoint operation involves the connection of several terminals to one host port. In
such an application, one local ME475A-R2 is used as a master unit, and it is con-
nected to several remote ME475A-R2s that are acting as slaves. Up to 25 ME475A-R2
slaves may be connected to one host ME475A-R2 master SRM, provided that the
computing hardware and software support that many terminal drops.
In a multipoint environment the master ME475A-R2 transmits continually. Initiation of
two-way communication is carrier-controlled by each “slave” ME475A-R2 unit.
To facilitate multipoint communication, the master ME475A-R2 should have its carrier
control DIP switch set to “constantly ON” (S1-8=OFF). Each slave ME475A-R2 unit
should have its carrier control DIP switch set to “controlled by RTS” (S1-8=ON).
Figure 4 illustrates a typical ME475A-R2 multipoint application.
XMT
RCV
XMT
RCV
G
G
RCV
XMT
RCV
XMT
To Shield (Optional)
}
One Pair
}
One Pair
