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KX-MB1500RUB/KX-MB1500RUW/KX-MB1520RUB/KX-MB1520RUW
6.4.
NCU Section (KX-MB1520 ONLY)
6.4.1.
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.
following is a brief explanation of each circuit.
6.4.2.
EXT. TEL. Line Relay (RLY100)
1. Circuit Operation
Normally, this relay switches to the external telephone side and switches to the open side while OFF-HOOK.
IC300 (U25) High Level
IC300 (U25) High Level
→Q201 ON→RLY100 (ON)
6.4.3.
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
board.
TEL LINE
→ PC103 (1, 2 → 4) → IC300 (L23)
6.4.4.
Pulse Dial Circuit
The pulse dial is generated by operating the transistor Q201 while OFF-HOOK (RLY100 ON) condition.
Make state:
IC300 (U25) High Level
Make state:
IC300 (U25) High Level
→ Q201 ON → RLY100 ON
Break state:
IC300(U25) LOW Level
IC300(U25) LOW Level
→ Q201 OFF → RLY100 OFF
6.4.5.
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.
amplified at pin (1) of IC201 and sent to the reception system at through the LPF.
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