Ncu Section - Panasonic KX-FP81BX Service Manual

KX-FP81BX / KX-FP81CX / KX-FP82CX
6.8.

NCU SECTION

6.8.1. GENERAL
This section is the interface between the telephone line and external telephone. It is composed of an EXT. TEL line relay (RL101),
bell detection circuit, pulse dial circuit, TAM interface circuit, line amplifier and sidetone circuits and a multiplexer.
6.8.2. EXT. TEL. LINE RELAY (RL101)
1. Circuit Operation
Normally, this relay switches to the external telephone side (break) and switches to the open side (make) while OFF-HOOK.
{ IC501 (38) High Level → CN501 (5) High Level } → CN101 (5) High Level → Q103 ON → RL101 (make)
6.8.3. BELL DETECTION CIRCUIT
1. Circuit Operation
The signal waveform for each point is indicated below. The signal (low level section) input to pin 39 of ASIC IC501 on the digital
board is read by ASIC and judged as a bell.
TEL LINE → PC102 (1, 2 - 4) → IC501 (39)
6.8.4. TAM INTERFACE CIRCUIT
This circuit is to switch between FAX receiving and the external TAM's message recording automatically. This circuit consists of an
EXT. TAM OFF-HOOK detect circuit, monitor transformer, multiplexer, amplifier, and VOX detect circuit.
For details, please refer to 6.10. TAM INTERFACE SECTION(P.167).
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