Sony WRR-862A, Service Manual, Page: 70 / 96

6-2
WRR-862A/862B
6-2
Tone squelch signal detector circuit
To detect the tone squelch signal of 32.768 kHz, which is
output from the transmitter, is detected with the filter con-
sisting of the crystal (X1061 and X1062 for tuner 1, X1161
and X1162 for tuner 2) and amplifier (IC1061 for tuner 1,
IC1161 for tuner 2), and comparator (IC1062 for tuner 1,
IC1162 for tuner 2).
Noise squelch signal detector
Noise squelch signal is detected with the High pass filter
(IC1011 for tuner 1, IC1111 for tuner 2) whose cut off fre-
quency is 87 kHz and comparator (IC1021 for tuner 1,
IC1122 for tuner 2).
Battery-tone signal detector circuit
To detect the battery-tone signal of 32.782 kHz, which is
output from the transmitter, is detected with the filter con-
sisting of the crystal (X1081 for tuner 1, X1181 for tuner 2)
and amplifier (IC1061 for tuner 1, IC1161 for tuner 2) and
comparator (IC1062 for tuner 1, IC1162 for tuner 2).
AF level detector circuit
Another audio signal branched from the main audio signal
path is detected by amplifier (IC1041 for tuner 1, IC1141 for
tuner 2) and used for AF level indication.
2. CPU block
The CPU (IC1301 for tuner 1, IC1401 for tuner 2) block
controls the following functions.
LCD display
Receiving channel or frequency display
Audio output level display
Battery exhaustion display
RF input level display
Accumulated operating time display
Error messages display
LED display
RF input level display
The RF input level is displayed in three levels by the LED lit
in green, red or turned off by using the RSSI signals shown
above. LEDs are two color type and independent for antenna
A and B, and tuner 1 and 2 (D1305 for antenna A of tuner 1,
D1304 for antenna B of tuner 1, D1405 for antenna A of
tuner 2, D1404 for antenna B of tuner 2).
Transmitter battery exhaustion display
Transmitter battery exhaustion is displayed by the LED us-
ing battery tone signal shown above. LEDs are independent
for tuner 1 and 2 (D1303 for tuner 1, D1403 for tuner 2).
Squelch (muting) control
The audio signal is muted when necessary by detecting the
RSSI signal, the tone squelch signal, and the noise squelch
signal.
PLL control
CPU controls the PLL IC (IC511 for tuner 1, IC561 for tuner
2) on the RX-60/74 board by using the frequency data stored
in the EEPROM (IC1302 for tuner 1, IC1402 for tuner 2).
Clock oscillator circuit
The clock oscillator circuit of the CPU for tuner 2 (IC1401)
oscillates the 4 MHz clock. This is also used as the clock for
the other CPU (for tuner 1, IC1301) and two PLL ICs
(IC511 for tuner 1, IC561 for tuner 2).