Telephone Line Interface - Panasonic KX-TSC10HGW Service Manual

When the bell signal is input between T/R, the signal is outputted at the speaker via the
following path:
Tel line R1/C1
11.2. Line Interface
In talk mode, SW101 becomes ON and Q104 base becomes High, causing Q104 and Q102 to turn
on and line loop is established.
The loop current flows as follows: D101(+)
The pulse signal that switches ON/OFF is output from pin 39 of the CPU.
Q104 and Q102 switch the line loop ON/OFF, generating the dial pulse signal.

11.3. Telephone Line Interface

11.3.1. Circuit operation
- On hook
Q102 cuts the DC loop current and the voice signal.
- Off hook
Q102 turns on to go into off-hook condition and the following
signal flow is for the DC loop current.
T D101 Q102
- The receiving signal flows:
TEL line Q102
Speaker
- The transmission signal flows:
MIC C422
TEL line
Pin 1 of IC2/Pin 8 of IC2
Q108
C105
R423 C424
Pin 5 of IC2
Q102 Q108
R114 D103
C401 R401
Q422 R428
18
PC1 SW1 Ringer
R114 D103.
D101 R
Q401 Q403
C427 Q108
Q404