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KX-FP207FX-S/FP218FX-S
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 (RL101)
1. Circuit Operation
Normally, this relay switches to the external telephone side (break) and switches to the tel line side (make) while OFF-HOOK.
{ IC501 (130) High Level → CN507 (14) High Level } → CN101 (14) High Level → Q111 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 23 of ASIC IC501 on the
digital board is illustrated.
TEL LINE → PC103 (1, 2 → 4) → IC501 (23): Bell
6.7.4. Pulse Dial Circuit and ON/OFF Hook Circuit
IC501 (130) → LOW LEVEL (MAKE) → Q111 ON (MAKE) → RL101 ON (MAKE) → TEL LINE
IC501 (130) → HIGH LEVEL (BREAK) → Q111 OFF (BREAK) → RL101 OFF (BREAK) → TEL LINE
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