Transmitter / Receiver (Cordless) - Panasonic KX-FC255CX-S Service Manual

6.9.

Transmitter / Receiver (Cordless)

Base Unit and Cordless Handset mainly consist of RF Module and DECT BBIC.
Base Unit and Cordless Handset transmit/receive voice signal and data signal through the antenna on carrier frequency.
6.9.1. Transmitter Block
The voice signal input from the TEL LINE interface goes to RF Module (IC28) through DECT BBIC (IC4).
The voice signal passes through the analog part of IC4 where it is amplified and converted to a digital audio stream signal. The
burst switch controller processes this stream performing encryption and scrambling, adding the various other fields to produce
the GAP (Generic Access Profile) standard DECT frame, assigning to a time slot and channel etc.
In IC28, the carrier frequency is changing, and frequency modulated RF signal is generated and amplified, and radiated from
antenna. Cordless Handset detects the voice signal or data signal in the circuit same as the following explanation of Receiver
Block.
6.9.2. Receiver Block
The signal of 19.2 MHz band (18.81792 MHz ~ 18.97344 MHz) which is input from antenna is input to IC28.
In IC28, the signal of 19.2 MHz band is down converted to 864 kHz signal and demodulated, and goes to IC4 as GAP (Generic
Access Profile) standard DECT frames. It passes through the decoding section burst switch controller where it separates out the
frame information and performs de-encryption and de-scrambling as required. It then goes to the DSP section where it is turned
back into analog audio. This is amplified by the analog front end, and goes to the TEL LINE Interface.
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KX-FC255CX-S