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6.7.
NCU Section
6.7.1.
General
NCU is the interface with the telephone line. It is composed of Bell detection circuit, Pulse dial circuit, Line amplifier and sidetone
circuits. The following is a brief explanation of each circuit.
6.7.2.
EXT. TEL. Line Relay (RLY101)
1. Circuit Operation
Normally, this relay switches to the external telephone side (break) and switches to the tel line side (make) while OFF-HOOK.
{ IC1 (44) High Level → CN7 (15) High Level } → CN101 (3) High Level → Q106 ON → RLY101 (make)
6.7.3.
Bell Detection Circuit
1. Circuit Operation
The signal waveform for each section is indicated below. The signal (low level section) input to pin 19 of ASIC IC1 on the dig-
ital board is illustrated.
TEL LINE → PC102 (1, 2 → 4) → IC1 (19): Bell
6.7.4.
Pulse Dial Circuit and ON/OFF Hook Circuit
IC1 (130) → LOW LEVEL (MAKE) → Q106 ON (MAKE) → RLY101 ON (MAKE) → TEL LINE
IC1 (130) → HIGH LEVEL (BREAK) → Q106 OFF (BREAK) → RLY101 OFF (BREAK) → TEL LINE
43
KX-FP701ME
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Troubleshooting
