Oki OF5600, Service Manual

Page: 307 / 448

Board Descriptions A - 23 OF 5300/5600 Serv Man, P/N 59278301
A3.2.4 M17 Circuit Diagram
1. Block diagram
The audio monitor circuit consists of IC11 (analog switch IC) and IC5 (amplifier) gener-
ates the following audio monitor.
•
Line monitoring
• Buzzer signals
Figure A3.2.4 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 RM 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
IOGA3. Output (high and low) from IC11 passes through the amplifier and 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 monitor will be switched off automatically after the elapse of speci-
fied time (about 5 sec).
2) Buzzer control
Alarm and other signals (key touch etc.) are input from CPU to this circuit as BZ
signal. The various buzzer signals are sounded under the control of CPU.
Block Diagram of Audio Monitor Circuit (Figure A3.2.4)
IC11
IC2
IOGA
CPU
RM
Analog
switch
IC5
Amplifier
CN8
1
2
Speaker
BZ
MONC0
MONC1
MONC2
0V 0VA
+5 V
0VA
from modem
TR1