Panasonic KX-FHD333BR Service Manual page 148

KX-FHD333BR
8.9.6. LINE AMPLIFIER AND SIDE TONE CIRCUIT
1. Circuit Operation
The reception signal output from the line transformer T101 is input to pin (2) of IC101 via C112 and R112 and then the signal
is amplified at pin (1) of IC101 and sent to the reception system at 11.6dB.
The transmission signal goes through C571 and R579 and enters IC511-pin (2), where the signal is amplified to about 24.8dB.
Then, it is output from pin (1) of IC101 and transmitted to T101 via C125 and R121. If the side tone circuit is not applied, the
transmission signal will return to the reception amplifier via C112 and R112. When the side tone circuit is active, the signal
output from IC101 pin (1) passes through C125, R123, C122, C115 and R115 and goes into the amplifier IC101 pin (3). This
circuit is used to cancel the transmission return signal.
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