Lesson l/Learning Event 5
(4) Miscellaneous Patching Module.
Miscellaneous patching modules
provide jacks for paralleling circuits and accessing regenerative repeaters,
mark and space battery, test circuits, and TTY monitoring equipment. Lamps
are usually associated with the jacks to indicate circuit activity.
b. DC Circuit Patch Bay.
(1) Functional Description.
The DC circuit patch bay is the central
point for-testing and alternate routing for DC circuits in the TCF. It is
also the point of interface for low-level DC circuits to VFCT equipment and
other DC transmission equipment, requiring the need for the appearance of
these circuits at the DC primary patch bay (see figure 1-16). All circuit
appearances at the DC circuit patch bay are low-level polar circuits (6
volts, 1 millampere).
At present, both unbalanced and balanced circuits
appear at the bay, but future systems are to be made up totally of balanced
circuits at this patch bay. Consequently, the DC circuit patch bay in the
typical present-day TCF has both D and K patches. In the newer TCFs it will
have only K patches.
(2) Application to Communications Security.
Military handbook on
communication security, requires low-level DC operation in both RED and
BLACK equipment areas.
Since it is intended that all military
communications eventually will be secure, as digital data terminal equipment
will be configured for low-level operation and the DC circuit patch bay will
remain the central testing and alternate routing point for all DC circuits
in the secure communications system.
(3) Send and Receive Patching Modules.
The send and receive patching
modules in the DC circuit patch bay are intended for use with either
balanced medium-speed or unbalanced low-speed data circuits. As in the DC
primary patch bay, one type patching module serves the send circuits and the
receive circuits. Figure 1-22 shows the front panel of a typical send and
receive patching module for a DC circuit patch bay.
Figure 1-23 is the
circuit diagram for a typical receive jack and figure 1-25 of the send jack.
The wiring for the two modules is similar, the only difference being the
application of the hold battery to the jackfield. If a cut key function is
required, it can be accommodated in the receive module by inserting a dummy
plug into the line side. This applies hold battery to the equipment circuit
to prevent the equipment from running "open".
Insertion of a dummy plug
into the equipment side of the send module performs the same function for
the send circuit.
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