Ncu Section - Panasonic KX-FP362CX Service Manual

7.9.

NCU SECTION

7.9.1. GENERAL
It is composed of bell detection circuit, pulse dial circuit, line amplifier, sidetone circuits, Remote FAX activation circuit, CPC
detection, and a multiplexer.
7.9.2. REMOTE FAX ACTIVATION CIRCUIT
1. Circuit Operation
After detecting the bell signal, another telephone connected to the same line switches to the FAX mode by DTMF signal.
TEL LINE → T101 → R120 → C113 → Q101(C-E) → C114 → R114 →IC101(2-1) → CN101(4) →{CN517(4) → C573 → R576
→ IC505(60)}
7.9.3. BELL DETECTION CIRCUIT
1. Circuit Operation
The signal waveform for each point is indicated below. The signal (low level section) input to pin 42 of ASIC IC501 on the digital
board is read by ASIC and judged as a bell.
TEL LINE → PC101 (1, 2 - 4) → IC501 (42)
7.9.4. PULSE DIAL CIRCUIT AND ON / OFF HOOK CIRCUIT
While OFF-HOOK, RLY101 is ON. Q102 turns on by pin (138) of IC501 as well. On the other hand, while ON-HOOK, Q102 turns
OFF by pin (138) of IC501, then the line turns OFF. ON/OFF-HOOK, controlled by pin (138) of IC501, makes the pulse dial
operation possible.
IC501 (138) LINE RLY Low Level → CN517 (12) → CN101 (12) → Q102 OFF → RLY101 OFF : DC Loop OFF
IC501 (138) LINE RLY High Level → CN517 (12) → CN101 (12) → Q102 ON → RLY101 ON : DC Loop ON
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KX-FP362CX