BENISON V5
- 7 -
3. DTMF Encoder
The CPU (IC8) is equipped with an internal DTMF encoder. The DTMF signalis output from pin 8, through
R75, and through the microphone amplifier (IC1), and is sent to the varicap of the VCO for modulation. At
the same time, the monitoring tone passes through the AF circuit and is output form the speaker.
4. CTCSS Encoder
The CPU (IC8) is equipped with an internal tone encoder, The tone signal (67.0 to 254.3Hz) is output from
pin 9 of the CPU to the varicap (D7) of the VCO for modulation.
5. CTCSS Decoder
The voice band of the AF output signal from pin 10 of IC5 is cut by sharp active filter IC2 (VCVS) and
amplified, then led to pin 4 of CPU. The input signal is compared with the programmed tone frequency code
in the CPU. The squelch will open when they match.
6. 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
32 of the CPU turns on D4. Then the oscillation frequency of X2 will be shifted about 300 ppm.
