Line Control Board - Panasonic UF-585 Service Manual

Panasonic UF-585 / 595
6.2.8

Line Control Board

The following shows a block diagram of the Line Control Board.
Line
Telephone
The Ring Detector consists of a photocoupler, PC1, and its peripheral circuits. The ringing signal is half-wave rectifier in the Ring
Detector, and transferred through the nCTON signal line to the CPU on the SCA/SCB PC Board. The CPU observes the signal to
distinguish from signals caused by chattering.
The Off-Hook Detector (External Telephone) circuit consists of the photocoupler, PC2, and its peripheral circuits. When PC2
detects loop current flow, it emits a Low active output signal (nHKOF) to the CPU which monitors it for a specified time. If the CPU
detects no change in the Low signal level, it determines that the External Telephone is Off-Hook.
208
PLS
CML
CML
Ring
Detector
PC1
+24V
CML
PC2
Off-Hook
PLS
Detector
HYBSR
HYSIG
PC1
PC2
LCU PCB SCA/(SCB) PCB
Modem
IC 11
(IC 8)
CPU
IC 1
CPU
IC 1
Port
IC17
(IC 7)