Panasonic KX-T2373MXW - 11 CIRCUIT OPERATION; 11.1. Bell Detector Circuit; 11.2. Line Interface

11 CIRCUIT OPERATION
11.1. Bell Detector Circuit
When the bell signal is input between T/R, the signal are outputted at the speaker via the following path: Tel line → R1/C1 →
D1 → Pin 1 of IC1 → Pin 8 of IC1 → C6 → T1 → C625 → Speaker
11.2. Line Interface
In talk status, L1 RLY output from pin 25 of IC801 changes to low level, causing Q103, Q101 to turn on and resulting in a line
loop.The loop current flows from D101(+) → Q101 → Q108 → R124 → D106 in that order, A pulse signal that repeated
switches between high and low logic is output from pin 26 of the CPU.This switches the line loop on and off, generating the dial
pulse signal.
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KX-T2373MXW