Ncu Section - Panasonic KX-FP342CX Service Manual

placed into the TX system.
7.8.1. ANALOG UNIT BLOCK DIAGRAM

7.9. NCU SECTION

7.9.1. GENERAL
This section is the interface between the telephone line and external telephone. It is composed of
an EXT. TEL line relay (RLY101), bell detection circuit, pulse dial circuit, TAM interface circuit, line
amplifier and sidetone circuits and a multiplexer.
7.9.2. EXT. TEL. LINE RELAY (RLY101)
1. Circuit Operation
Normally, this relay switches to the external telephone side (break)
and switches to the open side (make) while OFF-HOOK.
{ IC501 (138) High Level
High Level
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
7.9.4. 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
7.9.5. 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,
CN517 (12) High Level }
Q102 ON RLY101 (make)
PC101 (1, 2 - 4)
TAM INTERFACE
IC501 (42)
SECTION().
182
CN101 (12)