b. Cipher text.
(1) Squelch disabling.
When the KY-57 is turned ON and the MODE
switch is set to C, a cipher signal energizes relay K3, applying a ground to
the SQUELCH circuit (Figure 58).
This disables the SQUELCH.
Relay K3
applies the ground to the KY-57 RAD jack pin T.
The ground is applied
through the CX-13061/U to the J-3513/U J3 pin L. Within the J-3513/U the
ground is applied to K8 CIPHER SQUELCH relay. Energizing the relay, changes
K8B from P to C position. The ground is also applied through the J-3513/U
to the MT-1029 J22 pin P; through the MT-1029 J24 pin P to the RT P401;
where the ground is applied to the A5000 SQUELCH section disabling the
SQUELCH section of the RT.
NOTE:
KY-57 relay K3 and J-3513/U relays K6, K7 and K8 energize only
during the following conditions.
They are energized by the alarm
tone (beep) only in cipher mode.
Initial KY-57 turn on.
When receiving a cipher signal.
When transmitting a cipher signal.
When the KY-57 is initially turned ON (mode switch set to C). An
audio alarm test tone (beep) is generated within the KY-57 and
applied, through part of the received signal path, to the handset.
When the handset PTT switch is pressed, then released, the audio
alarm will clear. This keying action clears only the KY-57 alarm.
This action does not key the RT. After the alarm has been cleared
and the handset is again keyed, the RT will key.
(2) Cipher text.
The RF signal received at the antenna is applied
through the antenna system AS-1729/VRC, through the CG-1773/U, to the RT, RF
connector (Figure 58). The RF signal is applied to the RF and IF assemblies
and demodulated to an AF signal. Then the AF signal is applied through the
X MODE switch of the IF A4000 assembly (when set to X MODE) and to pin A of
the X MODE jack of the RT. The AF signal is applied from the RT, through
CX-13064/U to the J-3513/U J6 pin P, K8 energizes making K8B to C. Then the
signal is applied to the J-3513/U to J3 pin P through CX-13061/U pin P to
the RAD jack J3 pin A. The AF signal entering the KY-57 at the RAD jack J3
pin A is applied to the DECODER of the KY-57. If the code within the KY-57
is the same as the received signal, the DECODER will decode the signal. The
decoded signal is applied to the KY-57 AUDIO jack J1 pin B. Then the signal
is applied through the CX-13062/U to the J3513/U J1 pin B, through the
J3513/U J6 pin K and through the CX-13064/U, as it was with the plain text
signal to the RT. (Trace these circuits on your system diagram.)
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