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8. BLOCK DIAGRAM
9. CIRCUIT OPERATION
9.1. 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
9.2. Line Interface
In talk status, SW101 become ON and Q104 base changes to high level, causing Q104, Q102 to
turn on and resulting in a line loop.The loop current flows from D101(+)
R114
D103 in that order.
9.3. MODULE BLOCK DIAGRAM
9.3.1. Telephone Line Interface
9.3.1.1. Circuit operation
- On hook
Q102 is open, Q102 is connected as to cut DC loop current and cut
the voice signal.
- Off hook
Q102 turns on thus providing an off-hook condition (active DC
R1/C1
Pin 8 of IC2
Pin 5 of IC2
PC1
16
SW1
Ringer
Q102
Q108
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