Canon ir2016, ir2020 マニュアル

2-2

F-2-3

Signals from a 2-line telephone line are converted into transmission signals and reception signals (4 lines). It also serves to prevent intrusion of signals from the

modem into the reception circuit.

It turns on and off the relay within the circuit using the control signal from the Modem PCB to generate dial pulses so that dial signals will be generated by the fax

on a dial-pulse line.

Detects an off-hook state by monitoring the dirt current flowing in the circuit when the telephone connected to the extension telephone terminal is put off the hook.

The primary side of the NCU PCB is controlled by a line voltage of +48 VDC. The DC component is cut out by the work of a capacitor and, as a result, only audio

signals are converted into voltages suited to the level of the modem.

MODEM IC
FM336Plus

(IC1)

2-Line/4-Line

Conversion

Circuitry

Vref

generation

Formation

of DC Loop

Polarity

inversion

S relay

H relay

P relay

CML relay

Line signal

monitor

L1

T1

T2

CT2

CT1

L2

Hook

detection

Hook

detection

Detection

of CI

PATCH

(IC40)

Image Processor PCB

NCU PCB

Modem PCB

MPU
(IC1)