Harris Intraplex STL-160 Series, Installation & Operation Manual

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ACS-160 Series & STL-160 Series T1 Multiplexer Installation & Operation 2 – Functional Description
Version 2.11, August 2011
2-2 Harris Corporation
Intraplex Products
2.1.2 Drop and Insert Operation: the Signal Bus Role
The signal bus actually includes four buses:
● TX A bus
● RX A bus
● TX B bus
● RX B bus
In a terminal multiplexer, the channel modules place their transmit signals on the TX A bus. The CM-
5RB common module takes these signals and multiplexes them together for transmission on the T1
line. It also takes the incoming T1 signal, demultiplexes it, and places the resulting channel signals on
the RX-B bus, from which the channel modules take their individual receive data (Figure 2-2).
Figure 2-2. Terminal Multiplexer Signal Bus
Each channel module has a bus selection switch that sets its transmit and receive directions. This
switch is generally labeled TX-A BUS or TERM. Setting the TX-A BUS or TERM switch on ensures that
the module transmits on the TX-A bus and receives from the RX-B bus, as required in a terminal
multiplexer.
In a drop and insert multiplexer, setting the TX-A BUS or TERM switch on sets a channel module to
transmit and receive via the CM-5RB module designated as DI-A. Setting the TX-A BUS or TERM
switch off (up) sets a channel module to transmit and receive via the CM-5RB module designated as
DI-B, using the TX-B bus and the RX-A bus (Figure 2-3).
Figure 2-3. Drop and Insert Multiplexer Signal Bus
On some older channel module designs, there are two switches, one for the transmit side and one for
the receive side. These two switches should always be set to opposite directions. In a terminal
multiplexer, or to communicate via the DI-A port in a drop and insert multiplexer, set the switches to
transmit A, receive B. To communicate via the DI-B port in a drop and insert multiplexer, set the
switches to transmit B, receive A. Individual channel module manuals give the location and labeling of
these switches on the modules provided with this system.
As Figure 2-3 shows, in a drop and insert multiplexer, the RX-A bus connects to the TX-A bus, and the
RX-B bus connects to the TX-B bus. When there are no active channel modules in a drop and insert
multiplexer, all T1 signal time slots coming from each direction transfer to the outgoing T1 signal in
the other direction. When any transmit-only or full duplex channel modules are installed and active,
their output overrides the data coming through on their selected time slot(s). Data in time slots not in