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|  switch S801, is in the BB position.
output transformer T501. Detector
The decoded signals are amplified
diode CR501 is connected across
by V803 and coupled to second re-
the secondary of output trans-
ceiver audio amplifier V804.
former T501. When encoding equip-
ment is used, the incoming encoded
b. Audio Output Section.
signals are demodulated and ap-
(1) When NOR-BB switch S801 iS in the
plied to broadband cathode follower
NOR position, audio signals from
V802A. Tube V802A couples the en-
first audio amplifier V504 are
coded broadband signal to the
coupled to the second receiver
broadband decoding equipment.
audio amplifier V804 through
(2) Detector diode CR501 demodulates
squelch relay K801. Second re-
the 500-kc if. signal and applies
ceiver audio amplifier V804 ampli-
the audio signal to series noise
fies the audio signals to drive am-
limiter diode CR503. Detector
plifiers V805, V806, V807, and
CR501 also develops automatic
V808.
volume control (avc) voltage. Avc
(2) The output of the amplifiers is ap-
voltages are applied to the first
plied to audio output transformer
and second rf amplifiers through
T802. Audio is tapped off the sec-
rf avc gate CR505. If. amplifiers
ondary and applied to the local and
V301 and V302, and the first and
remote headsets and speakers and
second 500-kc if. amplifiers V501
to the fixed level audio terminal.
and V502, are controlled by avc
c. Squelch Circuit. The carrier squelch
voltage through if. avc gate CR504.
is controlled by the dc voltage developed
(3) Series noise limiter diode CR503
across the detector diode CR501 load.
clips noise peaks from the audio
When no signal is being received, squelch
signal. First audio amplifier V504
relay K801 is deenergized and the input
amplifies the audio output of the
circuits to the second audio amplifier
series noise limiter.
V804 are opened. When a signal of suf-
(4) The decoded audio output of the
ficient strength (determined by the setting
broadband equipment is applied to
of the SQUELCH control) is received, the
audio preamplifier V903 through
relay is energized and the circuits to the
relays K801 and K802, and NOR BB
second audio amplifier are closed.
switch S801, when the NOR BB
6
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