R46 Circuit Diagram (5/15) - Oki OKIFAX4550 Maintenance Manual

4.3

R46 Circuit Diagram (5/15)

1. Block diagram
R46-PCB circuit diagram (5/15) shown the consists of IC8 (analog switch IC) and IC11 (amplifier)
generates the following audio monitor.
• Line monitoring
• Buzzer signals
Figure A.21 shows the block diagram of audio monitor circuit.
2. Function
1) Line monitoring
Send and receive signals are input from the transformer on the NCU board to this circuit
as a R signal and the signal power is input to the IC8. The IC8 adjusts the monitor volume
by MONC0, MONC1 and MONC2 signal under the control of IC2 (IOGA6). Output (high
and low) from IC8 passes through the amplifier and is fed to the speaker as a SP signal.
* MONC0/MONC1/MONC2 signal: Volume control signal.
Note: In case of transmission mode, the monitor will be available during dialing, but the
2) Buzzer control
Alarm and other signals are input from IC2 (IOGA6) to this circuit as BZ signals. The various
buzzer signals are sounded under the control of CPU1.
+5V
RM
TR1
From MODEM
circuit
0VA
41309401TH Rev.4
monitor will be switched off automatically after the elapse of specified time (about 5
sec).
CPU1
64
SH7034
BZ
MONC0
MONC1
MONC2
IC2
75
76
IOGA6
77
Figure A.21 Block Diagram of Audio Monitor Circuit
IC8
Amplifier
Analog
IC11
switch
0VA
CN9
Speaker
1
2
0V
333 /