Lesson 1/Learning Event 4
(6) Equal Level Patch Bay. The equal level patch bay is the VF circuit
area central point for interfacing VF circuits with multiplex equipment. It
interconnects on the line side with the transmission media and on the
equipment side with the VF interface equipment. All VF circuits appear at
this bay with technical characteristics (same signal level) that enable
(a) Operational Characteristics. Like the jacks in the VF primary patch
bay, the jacks in the equal level patch bay are wired for normal-through
circuits, and connection is made to monitor jacks to permit circuit
monitoring without interruption. The monitor jacks may be used on both the
line and equipment side of the circuit jacks set, but must appear on the
line side as a minimum.
The equal level patch bay does not handle the
variety of circuits that the VF primary patch does. All circuits appearing
at the equal level patch bay are 4-wire circuits and do not involve
additional leads for signaling or echo suppressor control, etc.
The "equal level" is the level
defined for each circuit as the zero transmission level; therefore, the bay
is the zero Transmission Level Point (TLP) for all circuits.
(b) Patching Modules. The basic VF patching modules used in the equal
level patch bays are arranged the same as the 4-wire modules in the VF
primary patch bays.
(c) Interbay Trunking Modules.
These modules are used in the equal
level patch bays to carry circuits between equal level patch bays and
between the equal level and QATC bays. The trunks are basically used in the
same way that they are used in the VF primary patch bays.
access, line terminations, speaker jacks, inputs to meters and multiple
The main difference between the VF primary and the equal level
miscellaneous patching modules is the equal level modules provide for an
analog breakout monitor and for two 6-way/4-wire bridges for each station.
Figure 1-14 shows a front panel of this patching module.