Brother International IntelliFax-3550 Service Manual - Page 43
NCU PCB, Loop current detector
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3.4 NCU PCB The NCU PCB switches the communications line to telephone or built-in MODEM, under the control of the main PCB. 12 3 4 6 2 9 7 8 : 5 A 2 NCU PCB Circuit Diagram (U.S.A. versions) 1 Surge absorber 2 Noise filters 3 Line relay (CML relay) 4 Line transformer 5 Circuit related to the line transformer 6 High-impedance transformer circuit 7 Calling signal detector 8 Loop current detector 9 Dial pulse generator : Telephone circuit A Reference voltage generation circuit for the operational amplifier in |. III - 24
III –
24
3.4
NCU PCB
The NCU PCB switches the communications line to telephone or built-in MODEM, under the
control of the main PCB.
NCU PCB Circuit Diagram (U.S.A. versions)
1
Surge absorber
2
Noise filters
3
Line relay (CML relay)
4
Line transformer
5
Circuit related to the line transformer
6
High-impedance transformer circuit
7
Calling signal detector
8
Loop current detector
9
Dial pulse generator
:
Telephone circuit
A
Reference voltage generation circuit for the operational amplifier in
.
12
3
4
5
6
7
8
9
:
2
2
A