Ncu Pcb; Block Diagram Of The Ncu Pcb - Canon Super G3 Fax Board-J1 Service Manual

2 NCU PCB

2.1 Block Diagram of the NCU PCB

2.2 Functions of the NCU PCB
2-Line to 4-Line Conversion Circuit
It converts signals from a 2-line telephone line into transmission signals and reception
signals for a 4-line signal line. In addition, it prevents transmission signals from the mo-
dem from invading the reception circuit.
Dial Pulse Generation Circuit
The dial pulse generation circuit generates dial pulses by turning on and off the relay in
the circuit using control signals from the G3 fax control PCB, thereby enabling the fax
board to transmit dial signals using the dial line.
Off-Hook Detection Circuit
It identifies the condition of the telephone or the handset (option) connected to the tele-
phone terminal as being off- or on-hook in relation to the DC current flowing into it.
Circuit Voltage Conversion Circuit
The primary side of the NC board circuit is controlled by means of a line voltage of +48
VDC; the DC component is cut out using a capacitor, thereby converting only the audio
signals in voltages of a model level.
COPYRIGHT © 2001 CANON INC. 2000 2000 2000 2000
NCU PCB
2-line to 4-line conversion circuit
Line voltage conversion circuit
Dial pulse generation circuit
Off-hook detection circuit
F02 -201-01
CANON SUPER G3FAX BOARD-J1 REV.0 JUNE 2001
CHAPTER 2 BASIC OPERATION
2-3