The multiplexer converts the VF channels to one TDM-PCM signal for
transmission.
Radio set AN/GRC-103 receives the output of the TD-
660.
Low capacity systems do not require an interface unit.
The
radio set modulates this signal, along with the order wire signal
when present, on the selected RF carrier. The radio set then routes
the RF carrier signal to the antenna for transmission.
Our example uses an intermediate radio relay station. The antenna of
the relay station receives the RF signal and routes it to the radio
receiver of radio set AN/GRC-103.
The radio set demodulates the RF
signal to recover the TDM-PCM signal and the order wire signal.
These signals go directly to the transmitter of the other radio set
AN/GRC-103 via an interconnecting cable. Maximum separation between
the two radio sets is five feet. If you must separate the two sets
by more than five feet, you must install a multiplexer set TD-754 and
a coaxial cable link to condition the signal.
The transmitter of the second AN/GRC-103 modulates the signal on a
new RP carrier. It then transmits this RF signal in the direction of
the receive radio terminal.
The radio relay station operates
identically in either direction. The antenna at the receive terminal
picks up the RF signal from the relay station and routes it to the
AN/GRC-103 receiver.
The demodulator demodulates the signal to
recover the TDM-PCM and the order wire signals.
The demodulated
output goes to the multiplexer set where it converts back to 6/12 VF
channels.
The VF channels travel via cable to the telephone signal
converter.
The signal converter provides signaling and hybrid
facilities for the 6/12 VF channels. The output feeds switchboards,
field telephones, teletypes, facsimiles, or other 2-wire/4-wire VF
equipment.
Figure 1-21 is a block diagram of a low capacity cable system. The
function of the CV-1548 and the TD-660 are similar to those in the
radio system.
Note, however, that at the terminals and at the
repeater station, multiplexer sets TD-754 replace the radio sets.
The TD-754 conditions the output signals from the TD-660 for
transmission over coaxial cable.
Cable transmissions can travel up to 40 miles with the use of pulse
form restorer TD-206. Each mile of transmission cable requires a TD-
206.
A maximum of 39 TD-206s provide the 40-mile limit on cable
transmission.
Spans greater than 40 miles require an attended
repeater station.
1-26
SS0016
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