Its (Integrated Telephone System) And Monitor Section - Panasonic KX-F206TW Service Manual

KX-F206TW
3.3.

ITS (Integrated Telephone System) and MONITOR SECTION

Addition to original page 132 (6.9. ITS (Integrated Telephone System) and MONITOR SECTION)
6.9.5. HANDSET ALC DETECTION
1. Function
In some case, it is a standard requirement that the sound level of the handset should be low when the circuit current is large
(small line loss) and high when the circuit current is small (large line loss). This circuit detects whether the circuit current is large
or small. Changes in the level are performed by switching of Q202 and Q203.
2. Circuit Operation
The circuit current flows to R15 when in OFF-hook status. If the voltage at both ends of R15 exceeds approximately 0.7 V, Q206
turns on and PC2 also turns on. As a result, PC2-3 pin switching to high level, the bases of Q202, Q203 become a high level
and Q202, Q203 become on.
18