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6.6.
NCU Section
6.6.1.
General
NCU is the 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.
6.6.2.
Bell Detection Circuit
1. Circuit Operation
The signal waveform for each point is indicated below. The signal (low level section) input to pin 10 of BBIC IC4 on the digital
board.
TEL LINE → PC103 (1, 2 → 4) → IC902 (10)
6.6.3.
ON/OFF Hook Circuit
Normally (ON-HOOK condition), LINE RELAY (RLY100) is OFF. While OFF-HOOK, RLY100 turns ON. LINE RELAY is con-
trolled by pin 83 of IC902 through the Q201.
ON-HOOK:
IC902 (83) Low Level → Q201 OFF → RLY100 OFF
OFF-HOOK:
IC902 (83) High Level → Q201 ON → RLY100 ON
6.6.4.
Pulse Dial Circuit
The pulse dial is generated by operating the transistor Q201 while OFF-HOOK (RLY100 ON) condition.
Make state:
IC902(83) High Level → Q201 ON → RLY100 ON
Break state:
IC902(83) High Level → Q201 OFF → RYL100 OFF
6.6.5.
Line Amplifier and Side Tone Circuit
1. Circuit Operation
The reception signal output from the line transformer T100 is input to pin (2) of IC201 via C256, R224 and then the signal is
amplified at pin (1) of IC201 and sent to the reception system at through the LPF.
39
KX-MB2061CXB/KX-MB2061CX2/KX-MB2062CXB
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Table of Contents
Troubleshooting
