Ncu Section - Panasonic KX-FG2452CX Service Manual

KX-FG2452CX
6.8.

NCU Section

6.8.1. General
It is composed of bell detection circuit, pulse dial circuit, TAM interface circuit, line amplifier, sidetone circuits, Remote FAX activa-
tion circuit, CPC detection, and a multiplexer.
6.8.2. 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 → C118 → R125 → IC101(6-7) → C120 → R120 → IC101(2-1) → L111 → CN103(11) → {CN507(11)
→C767 → R769 → IC701(62)}
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 19 of ASIC IC501 on the dig-
ital board is read by ASIC and judged as a bell.
TEL LINE → PC102(1, 2 - 4) → {IC501(19)}
Note:
{ } : Inside the Digital Board
6.8.4. Pulse Dial Circuit and ON/OFF Hook Circuit
While OFF-HOOK, RL101 is ON. Q103 turns on by pin (44) of IC501 as well. On the other hand, while ON-HOOK, Q103 turns
OFF by pin (44) of IC501, then the line turns OFF. ON/OFF-HOOK, controlled by pin (44) of IC501, makes the pulse dial operation
possible.
{IC501 (44) LINE RLY Low Level → CN507 (16)} → CN103 (16) → Q103 OFF → RL101 OFF : DC Loop OFF
{IC501 (44) LINE RLY High Level → CN507 (16)} → CN103 (16) → Q103 ON → RL101 ON : DC Loop ON
Note:
{ } : Inside the Digital Board
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