Line Control Board - Panasonic DF-1100 Service Manual

6.2.8 Line Control Board

The following shows a block diagram of the Line Control Board.
E
Line
Telephone
The Ring Detector consists of a photocoupler, PC2, and its peripheral circuits. The ringing signal is
half–wave rectifier in the Ring Detector, and transferred through the nCTON signal line to the IC80 on the
FCB PC Board. The IC80 observes the signal to distinguish from signals caused by chattering.
The Off–Hook Detector (External Telephone) circuit consists of the photocoupler, PC1, and its peripheral
circuits. When PC1 detects loop current flow, it emits a Low active output signal (nHKOF) to the IC80 which
monitors it for a specified time. If the IC80 detects no change in the Low signal level, it determines that the
External Telephone is Off–Hook.
EK
PLS
CML
CML
C5
Ring
Detector
PC2
PC1
Off-Hook
Detector
+5V
PC4
+24V
EK
Q7
PC4
T2
PC2
PC1
+24V
CML
PLS
LCE PCB
System Description
Modem
(IC 631)
Port
(IC 80)
Port
(IC 80)
Port
(IC 80)
FCB PCB
6–25