Panasonic KX-TC1200NLB, Service Manual

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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
450 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 "VOLUME" key on the handset. Q2 controls the
volume. When CPU (VOL1)
becomes 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 39MHz band (39.9375~40.2125MHz) 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
it is converted to10.7 MHz and 450 KHz Intermediate by RF IC. The demodulated audio signal is
output from RF IC
(DET OUT) and passed through "Expander" process to reduce noise, then voice signal is led to
LINE AMP. The signal is
passed through TELEPHONE INTERFACE and Tel-line.
RX data (from Handset):
The data signal from handset (ex: Talk, ACK, COM) is also included in 39 MHz band same as the
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