Panasonic KX-TC1206TWB, Service Manual

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Amplifier device).
And the signal goes through the compressor of RF IC, it is output to transmitter circuit.
The signal of the data sent to the handset is applied in the anode of the variable capacitor diode
(VARICAP : DV1).
The capacitor of VARICAP is changing in accordance with the voice signal from telephone line
interface or TX DATA signal from
CPU. Therefore, the carrier frequency which is generated by TXVCO will be changing, and
Frequency modulated RF
signal is generated and amplified by RF AMP(Q3, Q4, T5). It pass through the Duplexer DPX1
and radiated from Antenna.
The signal is transmitted from the base unit and received by the handset antenna and amplified
by RF amplifier (Q1) through
DPX1 as shown in
BLOCK DIAGRAM (HANDSET) (). And then it is converted to 10.7 MHz and
455 KHz Intermediate frequency by RF IC and related components.
The demodulated audio signal is output from RF IC (DET OUT) and passed through "Expander"
process to reduce noise, then
voice signal amplified by "Receiver amplifier" is output to receiver (REC1).
The receiver loudness is adjustable using "LOUD" key on the handset. Q2 and Q3 control the
volume. When CPU (VOL1)
becomes low, the volume becomes "MID", while CPU (VOL1, 2) become low, the volume
becomes "HIGH".
TX data (to Handset)
CPU (VTX) becomes low to turn on the transmission power transistor Q2, and CPU (TX-data)
sends data signal. It is
FM-modulated by TXVCO and driven by RF AMP, then transmitted to the handset.
16.6.2. Handset to Base
Circuit Operation:
The voice signal from the handset user is picked up by the microphone (MC1), voice signal
passes through "Compressor"
process to reduce noise as shown in
BLOCK DIAGRAM (HANDSET) (). And the voice is FM-
modulated by
VARICAP (DV1).
The carrier frequency is generated by TX VCO. The transmitter power transistor Q4 is turned on/
off by CPU (VTX).
The carrier signal is amplified by RF AMP and sent to the handset duplexer and antenna.
The signal of 49MHz band (49.670~49.99MHz) which is input from ANT is filtered at DPX1 as
shown in
BLOCK DIAGRAM (BASE UNIT) (), then it is input to RF IC.
The signal input to RF IC is converted through Mixer inside of RF IC, RF filter (CF1, CF2) and
Expander.
The signal is transmitted from the handset and received by the base unit antenna and amplified
by RF amplifier Q1, then
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