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22
22. Sub-Rate Data (SRD-2/SRD-4/SRD-4N)
22.1 Description
Three versions of the SRD Module are currently
available. The SRD-2 Module provides two RS-
232 data circuits per DS0, and the SRD-4 Module
one RS-232 and one RS-485 circuit per DS0. The
SRD-4N includes extra circuitry to permit
extending RS-485 LANS between stations. All
versions support a total of four 0-9600 bps asyn-
chronous data channels over two DS0 channels.
The four circuits operate independently of each
other, simultaneously carrying their data/control
signals over two FOCUS DS0 channels, or time
slots.
The SRD module does not process the data
passing through it. Data and modem control
signals, such as those in Table 22-1, are trans-
ferred transparently across the FOCUS DS0
channels.
The Module's interface, consists of a DB25
Female connector that is fitted to the rear of the
chassis which electrically connects it to the SRD
Module. Three interfaces are available for the
SRD module, SRD-2, see Figure 22-1, SRD-4 &
SRD-4N, see Figure 22-3. The interface cables
have two or four DB9 Female connectors,
depending on which version module you have, for
directly connecting your RS-232 equipment, with
the SRD-2, SRD-4N and the SRD-4.
Figure 22–1. SRD-2 Interface Module.
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