Table of Contents
Advertisement
6.7.
NCU Section
6.7.1.
General
It is composed of bell detection circuit, pulse dial circuit, line amplifier, sidetone circuits.
6.7.2.
Bell Detection Circuit
1. Circuit Operation
The signal waveform for each point is indicated below. The signal (low level section) input to pin 19 of ASIC IC1 on the digital
board.
TEL LINE → PC102 (1, 2 → 4) → CN101 (9) → {CN2 (9) → IC1 (19)}
Note:{
} : inside the digital board
6.7.3.
ON/OFF Hook Circuit
Normally (ON-HOOK condition), LINE RELAY (RLY101) is OFF. While OFF-HOOK, RLY101 turns ON. This LINE RELAY is con-
trolled by pin 130 of IC1 through the Q7.
ON-HOOK:
IC1 (130) Low Level → Q7 OFF → RLY101 OFF
OFF-HOOK:
IC1 (130) High Level → Q7 ON → RLY101 ON
6.7.4.
Pulse Dial Circuit
Make state:
IC1 (130) High Level → Q7 ON → RLY101 ON
Break state:
IC1 (130) Low Level → Q7 OFF → RLY101 OFF
37
KX-FT981LA-B / KX-FT987LA-B
Advertisement
Table of Contents
Troubleshooting
