Circuit Diagram (3/13) - Oki OKIFAX4550 Maintenance Manual

3.3 46F Circuit Diagram (3/13)
1. Block diagram
46F-PCB circuit diagram (3/13) shown the consists of IC11 (analog switch IC) and IC5 (amplifier)
generates the following audio monitor.
• Line monitoring
• Buzzer signals
Figure A.8 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 IC11. The IC11 adjusts the monitor volume
by MONC0, MONC1 and MONC2 signal under the control of IOGA4. Output (high and low)
from IC11 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 IOGA4 to this circuit as BZ signals. The various
buzzer signals are sounded under the control of IOGA4 (CPU).
+5 V
RM
TR501
From MODEM
circuit
0 VA
41309401TH Rev.4
monitor will be switched off automatically after the elapse of specified time (about 5
sec).
IC2
IOGA4
BZ
MONC0
MONC1
MONC2
IC2
IOGA4
Figure A.8 Block Diagram of Audio Monitor Circuit
IC11
Amplifier
Analog
IC5
switch
0VA
CN9
Speaker
1
2
0V
312 /