Panasonic KX-TC2000SNB, Service Manual

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- first/ second mixer
- Amplifier for transmission and reception
- Additionally,
- Power Supply Circuit
- Reset Circuit
- Charge Circuit
- Telephone Line Interface Circuit
Handset consist of the following ICs as shown in BLOCK DIAGRAM.
- CPU: IC2
- All data signals (forming/analyzing ACK or CMD signal*)
- All interfaces (ex; LED, Key, Buzzer, Detector Circuit, Charge,
Battery Low)
- RAM for keeping the data (CH Number, ID Code, etc.)
- RF IC:IC1
- PLL Oscillator
- Detector
- Compress/Expander
- first, second mixer
- Amplifier for transmission and reception
*Refer to EXPLANATION OF CPU DATA COMMUNICATION ().
19.2. Power Supply Circuit
The power supply to the CPU (Digital, Analog) and RF IC from AC Adaptor (+12V) is shown in
the diagram below.
The base unit power supply is DC12V. The handset's power is supplied from 3.6V battery (Nickel-
Cadmium battery) which is
installed in the handset.
Power supply for transmitter is turned on by a press of "Talk" key on the handset. During the
stand-by mode, the unit stops
transmitting but receives the signal.
Also during on-hook condition (the handset is placed on the base unit), backup power for
memory of the last dialed number is
supplied through the battery. The memory of this unit is not backed up by the current from
the telephone line.
The base unit DC power supply is regulated by Q18, the CPU power is regulated by Q19. The
Q401, Q403 detects AC Adaptor power failure and maintains the unit security code.
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