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TM 11-5895-1012-10
lead when a signal is received from the ringdown
trunk circuit. It also receives signals over an E-lead
from a signaling circuit and transmits 20 Hz signals to
a ringdown trunk circuit. This equipment can be ar-
ranged to operate with signaling frequencies other
than 20 Hz when required.
d. E&M Signal-Lead Extension Circuits (DX1 and
DX2). These signal-lead extensions units are designed
to interconnect two signaling and supervision circuits
when the metallic resistance between users exceeds
patch panel has four cable connectors mounted on the
operational limits. They are also used to interconnect
rear of the panel. As shown in figure F0-2, C1 and C3
an E&M signaling circuit to a distant trunk circuit
are used to bring the transmit and receive circuit leads
which uses single frequency signaling. E&M signal-
into the panel. C2 and C4 are known as the normal-
lead extension circuits are usually required where the
through connectors. The normal-through wiring which
connecting facility (cable) resistance exceeds 25 ohms
connects the line side to the equipment side of the
(50 ohm loop). These circuits, which have been coded
panel is routed through these connectors. Thus
DX1 and DX2, are always used in pairs (a DX1 being
is provided to the normal-through connections for fu-
connected to the trunk relay circuit and DX2 being
ture uses, such as automation of the Technical Control
connected to a single frequency signaling unit). They
may be used in any combination, DX1 at one end of the
b. 6-Wire Primary Voice Frequency Patch Panel
circuit and DX2 at the other, or with like units at each
(E&M Signaling). The 6-wire Primary Patch Panel is
end of the circuit. This equipment usually functions
over metallic circuits with loop resistance up to 5000
e. Pulse Link Repeater. The pulse-link repeater cir-
cuit connects two signaling circuits, using E&M leads,
panel between them. The E&M patch panel provides
signaling jack appearances for the 12 channels above,
by converting an incoming E-lead potential to an out-
as well as the 12 channels below it. A front view of an
going M-lead potential in both directions of transmis-
sion. This equipment does not connect to or affect the
E&M signaling patch panel is shown in figure 2-15B
and the interconnection diagram in figure 2-16. The
talking it is connected in the signaling path only.
odd numbered jacks serve the E&M signaling leads of
2-35. Vf and E&M Panels
the vf above it while the even numbered jacks serve
the E&M signaling leads of the vf panel below it. The
A voice frequency jackfield is designed as an area in
top row of jacks is electrically toward the line, and the
the Technical Control Facility where voice frequency
second row of jacks is toward the Technical Control
circuits and their associated signal and control leads
Facility equipment. As with other patch panels, the
can be patched, monitored and tested. A patch panel is
normal&rough connections between the line and
a signal unit in the jackfield. There are four types of
equipment sides of the panel (row 1 and row 2) are
voice frequency patch panels in the TCF; the Equal
brought out to a normal&rough connector for future
bevel., the 4-wire, the 6-wire primary, and the 2-wire
primary patch panels. Each panel serves a different
c. 2-Wire Primary Voice Frequency Patch Panel.
function as described in paragraph 2-17.
This panel is similar to the 6-wire vf patch panel in
a. Equal Level and 4-Wire Primary Patch Panels
that it has four rows of jacks for line side, equipment
(fig. 2-15A) Each Equal Level and 4-wire primary
side, and monitoring operations. Since it is a 2-wire
patch panel contains 12 channels. Each channel occu-
panel, it can hold 24 channels. Refer to figure 2-17 for
pies a paired jackset (a jack& consists of 4 jacks ar-
the interconnection diagram of a 2-wire patch panel.
ranged vertically) of the panel as shown in figures
2-15 and F0-2. The receive circuit occupies the left
2-36. Dc Patch Panels
jackset (odd numbered jacks) in each paired jackset,
a. Primary Dc Patch Panel.
and the transmit circuit occupies the right jackset
(1) Panel Description (fig. 2-15). The primary dc
(even numbered jacks) of each paired jackset; there-
patch panel is that equipment within the Technical
fore, the jacks are alternately labeled REC and
TRANS. The top row of jacks are labeled LINE and are
electrically toward the line or away from the Technical

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