14 CIRCUIT OPERATION
14.1. 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 → Pin 8 of IC2 → Pin 5 of IC2 → PC1 → SW1 → Ringer
14.2. 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(+) → Q102 → Q108 → R114 → D103 in that order, A pulse signal that repeated
switches between high and low logic is output from pin 73 of the CPU. This switches the line loop on and off, generating the
dial pulse signal.
14.3. MODULE BLOCK DIAGRAM
14.3.1. Telephone Line Interface
14.3.1.1. 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 current flow through the circuit) and the following signal flow is
for the DC loop current.
T → D101 → Q102 → Q108 → R114 → D103 → D101 → R
·
The receiving signal flows:
TEL line → Q102 → C401 → R401 → Q401 → Q403 → Q404 → H/S SP
·
The transmission signal flows
MIC → Q422 → R428 → C427 → Q108 → TEL Line
29
KX-TSC11AGW
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