Ncu Section - Panasonic KX-FT901CX-B Service Manual

8.8.

NCU SECTION

8.8.1. GENERAL
This section is the interface between the telephone line. It is composed of bell detection circuit, pulse dialing circuit, CPC detection
circuit, line amplifier, sidetone circuits and Remote FAX activation circuit.
8.8.2. LINE RELAY (RLY1)
1. Circuit Operation
Normally, this relay switches to the external telephone side (Break) and switches to the open side (make) when the unit starts
facsimile communication.
[IC1 (130) High Level → CN2 (7)] → CN1 (7) → Q10 ON → RLY1 (make)
8.8.3. BELL DETECTION CIRCUIT
1. Circuit Operation
The signal waveform for each section is indicated below. The signal (low level section) input to pin 23 of ASIC IC1 on the digital
board is read.
TEL LINE → PC2 (1, 2 - 4) → CN1(11) → [CN2(11) → IC1(23)]
8.8.4. PULSE DIALING
[IC1 (130) High Level → CN2 (7)] → CN1 (7) → Q10 ON → RLY1 (make)
KX-FT901CX-B / KX-FT903CX-B / KX-FT901CX-W / KX-FT903CX-W / KX-FT901CX-S / KX-FT903CX-S
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