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ELECTRICAL CIRCUITS
4 - 7
4
EU/AU/AS/C models
Fig. 4-7
The dial pulse generation circuit consists of the photocoupler (IC1), the ASIC (IC23) on the MAIN board
and the other peripheral devices. It generates the dial pulses in the FAX transmission and dialing to the
outside.
The ASIC makes the CML1 signal become HIGH to connect the line to the MODEM side. To generate
the dial pulses, the ASIC makes the LD1 signal become HIGH to turn ON Q6. This allows the photocou-
pler to come on and the current flows through the line for sending a dial attempt.
Signal Name Type Active Description Destination
LD1 O H Line 1 Dial Pulse Generation Signal Q6
T1
AG
CML1
LD1
3
4
AG
CN3
Lb
La
0
1
0
1
10
8
3
5
1
2
6
4
12
9
4
1
+12V
RLY3
CML relay
4
3
a2
b2
2
5
3
4
27
61
FAX board
NCU board
SG
+5V
External
telephone
Line
IC1
Q6
Q4
CN4
CN262
IC23
ASIC
Ring signal
detection
circuit
Line path
switching
circuit
CN5
CN5
27
61
144
143
MAIN board