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KX-TS580MXB/KX-TS580MXW/KX-TS580MXR/KX-TS580MXC/KX-TS580MXJ
4.2. Circuit Operation
4.2.1. Bell Detector Circuit
When the bell signal is input between T/R, the signal are outputted at the speaker via the following path:
T / R → R1 / C1 → D1 / LED1(2AP) → IC1 (pin1) → IC1 (pin8) → PC1 → C5 → SW1 → T1 → Speaker
4.2.2. Line Interface
In talk status, SW101 become ON and Q103 base changes to high level, causing Q103, Q101 to turn on and resulting in a line
loop. The loop current flows from D101(+) → Q101 → Q107 → R119 → 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.
4.2.3. Telephone Line Interface
4.2.3.1. Circuit operation
• On hook
Q101 is OFF, on-hook condition where DC loop is disconnected and voice signal flow is cut.
• Off hook
Q101 is ON*, providing an off-hook condition (active DC current flow through the circuit) and the following is the signal flow:
T → POS101 → L101 → D101(+) → Q101 → Q107 → R119 → D103 → D101(-) → L102 → R
* Handset mode : SW101 ON after handset off-hook
* SP-Phone mode : IC801 (pin 70) output high logic after pressing SP-Phone button.
• The receiving signal flows:
LINE → Q101 → C109 → C401 → R401 → Q401 → Q402 → Q403 → SP (handset)
• The transmission signal flows
MIC (handset) → Q422 → R433 → C432 → Q107 → Q101 → LINE
4.2.3.2. Tone Detect
This circuit is used to sense the status of the line (busy tone or dial tone) during Auto Redial.
4.2.3.2.1. Circuit operation
D101 → Q101 → C201 → R201 → R205 → Pin 5 of IC201 → Pin 1 of IC201 → D202 → R208 → Q201 → Pin 87 of IC801.
When the subscriber hangs-up, check the intermittent tone. If cycle tone is detected, the collector of Q201 goes to a low logic.
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