Alinco DR-235 Service Manual page 12

2. Dimmer Circuit
3. Reset and Backup
4. S(Signal) Meter Circuit
5. DTMF Encoder
6. Tone Encoder
7. DCS Encoder
8. CTCSS, DCS Decoder
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The dimmer circuit makes the output of pin 13 of CPU (IC1) into "H" level at set
mode, so that Q9 and Q3 will turn ON to make the lamp control resistor R84
short and make its illumination bright. But on the other hand, if the dimmer
circuit makes pin 13 into "L" level, Q9 and Q3 will turn OFF, R84's illumination
will become dimmer as its hang on voltage falls down in the working LED (D11,
D2, D5, D3 and D6).
When the power form the DC cable increases from Circuits 0 V to 2.5 or more,
"H" level reset signal is output form the reset IC (IC4) to pin 33 of the CPU
(IC1), causing the CPU to reset. The reset signal, however, waits at 100, and
does not enter the CPU until the CPU clock (X1) has stabilized.
The DC potential of pin 16 of IC106 is input to pin 1 of the CPU (IC1), converted
from an analog to a digital signal, and displayed as the S-meter signal on the
LCD.
The CPU (IC1) is equipped with an internal DTMF encoder. The DTMF signal
is output from pin 10, through R35, R34 and R261 (for level adjustment), and
then through the microphone amplifier (IC114:A), 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.
The CPU (IC1) is equipped with an internal tone encoder. The tone signal (67.0
to 250.3 Hz) is output from pin 9 of the CPU to the varicap (D122 and D123) of
the VCO for modulation.
The CPU (IC1) is equipped with an internal DCS code encoder. The code
(023 to 754) is output from pin 9 of the CPU to the varicap (D124) of the
PLL reference oscillator. When DCS is ON, DCS MUTE circuit (Q126-ON,
Q133-ON, Q132-OFF) works. The modulation activates in X103 side only.
The voice band of the AF output signal from pin 1 of IC104:A is cut by sharp
active filter IC104:B and C (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. During DCS, Q108 is ON, C156
is working and cut off frequency is lowered.