Panasonic KX-TS105LXW Service Manual page 21

control to automatically adjust for changing ambient conditions.
1. Transmission signal path:
The input signal from the microphone is sent through the circuit
via the following path:MIC
Pin 3 of IC601
2. Reception signal path:
Signals receive from the telephone line are outputted at the
speaker via the following path:Tel line
R600 C603
IC601 Pin 15 of IC601
3. Transmission/Reception switching
The comparison result between TX and RX outputs as a DC level
of Pin 25 of IC601.TX level is high ...... Pin 25 = Pin 21 - 6mVRX
level is high ...... Pin 25 = Pin 21 - 150mVComparator output is
connected to the attenuator control inside of IC601.
4. Voice detector
The output of the mic amp (Pin 10 of IC601) is supplied to Pin 13 of
IC601 as a control signal for the voice detector.
5. Attenuator control
The attenuator control detects the setting of the volume control
through Pin 24 of IC601 to automatically adjust for changing
ambient conditions.
11.3.2. Telephone Line Interface
11.3.2.1. Circuit operation
- On hook
Q101 is open, Q101 is connected as to cut DC loop current and cut
the voice signal.
- Off hook
Pin 9 of IC601
Pin 4 of IC601
Pin 27 of IC601
Speaker.
R601 C602
Q108
Pin 26 of IC601
21
Pin 10 of IC601
Q108 Tel line.
Q109 C112
Pin 19 of