COPYRIGHT © 2001 CANON INC.
2000 2000 2000 2000
CANON SUPER G3 FAX BOARD-J1 REV.0 JUNE 2001
CHAPTER 2 BASIC OPERATION
2-4
3 Off-hook detection PCB
3.1 Block Diagram of the Off-hook detection PCB
F02-301-01
3.2 Functions of the Off-hook detection PCB
Power Supply Circuit Used to Detect an Extension
To detect the connection of an extension, the Off-hook detection PCB generates a DC
voltage of +48 V to supply to the extension terminal. A transformer is used to separate the
primary side and the secondary side by an electrical means.
All-Day Power Supply Circuit
The main controller circuit generates all-day 5 VB from all-night +3.3 VB. To operate the
FC detection circuit of the G3 fax control PCB at all times, the +5 VB voltage is sent to
the G3 fax control PCB by way of the Off-hook detection PCB.
Off-hook detection PCB
Power supply circuit for
detection of extension
telephone
All-day power supply
relay circuit
J713
J714
J712
J715
From
composite power
supply PCB
+24V
From
main controller
PCB
5V all-day
voltage
supplies voltage for
detection of off-hook
state
5V all-day power
supply
