Panasonic KX-FT21BX Service Manual page 168

KX-FT21LA
6-4. LINE AMPLIFIER AND SIDE TONE CIRCUITS
(1) Circuit Operation
The reception signal received as output from line transformer T1 is given as input to C14, R13 and IC2 pin(2).
Then it is input to the reception system at an amplifier gain of 5.9 dB from pin(2).
The transmission signal is input from CN1 pin (11), and output to the TEL line through C6, R14 and T1. Without a side tone
circuit, the transmission signal would return to the reception amplifier via C6 and R14. Here, the signal output from CN1
pin(11) passes through C6, C36 and R12 and enters the amplifier IC2 pin (3). This is used to cancel the return portion of
the transmission signal. This is the side tone circuit.
Transmission Signal: CN1(11) C6
Reception Signal: T E L L I N E - T 1 - C 1 4 - R 1 3 - I C 2 ( 2 , 3 - 1 ) - C N 1 ( 1 0 )
R14 T1 TEL LINE
|
C36
|
R12
|
C10
|
R11
|
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(Side Tone)