Lesson 3/Learning Event 4
(1) The Telegraph Terminal AN/FCC-19
enables DC
monitoring of
individual FSK channels of telegraph communication by receiving and
channelizing a composite VF terminal signal.
This capability is made
possible by the standardization of channel frequencies in multichannel
telegraph carrier terminals.
Although the AN/FCC-19 has a transmission
capability, it is not normally used for that purpose.
It is a receive
only system.
The channel assignment and the signaling sense of the
incoming signal must be known.
(2) A DC jackfield is provided for patching any one of the 16 channels
in the AN/FGC-19 to the distortion analyzer or the teletypewriter monitor
(AN/FGC-69).
(3) The AM-1220/FG is used in a receive only system to convert on-off
tone signals to DC for monitoring.
(4) The station alarm provides visual and audible indications for 20
separate check points.
e. Ringdown Converter Bay.
Bay 12 contains 150 ringdown converters
which are used for interconnecting 20-Hz ringing with E and M signals.
(1) When an E lead signal is received form the SF unit, a 20-Hz ringing
signal is applied to the 2W telephone line.
(2) When a 20-Hz signal is received from the 2W line, it is detected by
the converter which applies an M lead signal to the SF unit.
f. Hybrid Bay.
Bay 13 contains 100 plug-in hybrids, along with the
balancing resistors, for 2W-4W conversion.
g. Combined Distributing Frame (CDF).
The CDF shown in figure 3-9
consists of 76 vertical terminal blocks for circuit wiring, and 9
protector assemblies for outside cables.
A total of 15 vertical frame
members support all blocks and protector assemblies.
All wiring of
circuits is accomplished on the vertical blocks from the front. There are
no horizontal blocks on the other side of the frame, as is usually the
case in fixed-station installations.
All circuit wiring is accomplished
by jumpers on the vertical blocks of the CDF; none is done anywhere else,
except for maintenance purposes.
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