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KX-FP101AL
6.8.
NCU SECTION
6.8.1.
GENERAL
NCU is the interface with the telephone line. It is composed of Renmote FAX activation circuit, Bell detection circuit, Pulse dial
circuit, CPC detection circuit and Line amplifier and sidetone circuits. The following is a brief explanation of each circuit.
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 → T102 → CN102 (9) → {CN502(9) → C648 → R670 → IC551 (20-31) → R649 → C631 → IC505 (60)}
6.8.3.
BELL DETECTION CIRCUIT
1. Circuit Operation
The signal waveform for each section is indicated below. The signal (low level section) input to pin 148 of ASIC IC501 on the
digital board is illustrated.
TEL LINE → PC103 (1, 2 → 4) → IC501 (148): Bell
6.8.4.
PULSE DIAL CIRCUIT AND ON/OFF HOOK CIRCUIT
While OFF-HOOK, RL101 is ON. Q108 turns on by pin (24) of IC501 as well. The signal level at the photocoupler PC101 pin (2)
becomes a low level by pin (46) of IC501. On the other hand, while ON-HOOK, Q108 turns OFF by pin (24) of IC501, then the line
turns OFF. The signal level at the photocoupler PC101 pin (2) becomes a high level by pin (46) of IC501. ON/OFF-HOOK,
controlled by pin (46) of IC501, makes the pulse dial operation possible.
ON-HOOK: IC501 (24) LINE RLY Low Level → CN501 (6) → CN101 (6) → Q108 OFF → RL101 OFF
OFF-HOOK: IC501 (24) LINE RLY High Level → CN501 (6) → CN101 (6) → Q108 ON → RL101 ON
PULSE (BREAK): IC501 (46) HIGH Level → PC101 (2) High level → PC101 OFF →DC Loop OFF
PULSE (MAKE): IC501 (46) LOW Level → PC101 (2) Low level → PC101 ON →DC Loop ON
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Troubleshooting
