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8. CTCSS, DCS Decoder
The voice band of the AF output signal from pin 9 of IC103 is cut by sharp
active filter IC111 and amplified, then led to pin 80 of CPU. The input signal is
compared with the programmed tone frequency code in the CPU. The squelch
will open when they match.
9. Clock Shift
In the unlikely event that CPU clock noise is present on a particular operating
frequency programmed into the radio, you can shift the CPU clock frequency
to avoid the CPU clock-noise. The output signal from pin 8 of the CPU turns
on Q127. Then the oscillation frequency of X104 will be shifted about 200
ppm.
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