Charge Circuit; Telephone Line Interface - Panasonic KX-TC1201BXB Manual

16.4. Charge Circuit

Circuit Operation:
When charging the handset on the base unit, the charge current is as follows;
DC (JK2) L8 D6 L7 CHG+(Base) [CHG+(Handset) L4 Q9
BATT(1)....Battery....BATT(2) L5
CHG-(Handset)] CHG+(Base) L5,
In this way, the CPU on both unit detects the fact that the battery is charged.
The charge current is controlled by switching Q701 of Handset. The battery is charged in normal
mode for 10 hours and then in trickle mode.

16.5. Telephone Line Interface

Function:
- Bell signal detection
- ON/OFF hook and pulse dial circuit
- Side tone circuit
Bell signal detection and OFF HOOK circuit:
In the idle mode, Q103 is open to cut the DC loop current and decrease the ring load. When ring
voltage appears at the Tip (T)
and Ring (R) leads (When the telephone rings), the AC ring voltage is transferred as follows:
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