Brother FAX-170 Service Manual page 30

1
3
3
-1
3
-2
1 Connector for the power supply PCB
1-1: CR1, recording head on/off relay
2 3-terminal regulator which eliminates unstabilized components of the +8V source to
generate stabilized 5V source.
3 Connector for the NCU
3-1: Power for the NCU
3-2: Signals from the telephone
4 Analog signal selectors
4-1: Selects either input signals from the handset or those from the MODEM.
4-2: Selects either RL1 or RL2 signals inputted from the communications network.
4-3: Selects either sound signals (e.g., alarm beeps, key clicks and ringer sounds) generated
by the FAX engine or signals selected by 4-2.
Amplifier circuit for signals outputted from the MODEM.
5
6 Analog front end IC which processes the analog I/O signals from/to the MODEM.
7 Amplifier & shaper circuit for signals inputted from the communications network.
8 Telephone circuit for transmitting signals.
9 Speaker amplifier circuit which amplifies sounds issued from the above analog signal
selector 4-3 and feeds them to the speaker.
Connector for the speaker
:
a Speaker volume control circuit
a-1: VOL1
a-2: VOL2
Speaker volume
1
-1
2
4
-1
4
-2
7
Main PCB Circuit Diagram 4/4
OFF
OFF
High
5
4
-3
a
-1
8
a
ON ON
OFF ON
Medium Low
III – 23
6
9
a
-2
(ON: Closed OFF: Opened)
: