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4.2.3
Dial pulse generation circuit
NA/TW models
NCU board
+12V
1
4
Lb
9
Line
3
La
4
3
a2
External
telephone
4
b2
The dial pulse generation circuit consists of the diode bridge (DB1), photocoupler (PC1), 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 pulse, the ASIC makes the LD1 signal become HIGH to turn ON Q53. This allows the photo-
coupler to come on and the current flows through the DB1 to send the dial pulses to the line.
Signal Name
Type
LD1
GD-1220/1221
ELECTRICAL CIRCUITS
C5
R4
RLY2
CML relay
12
1
8
0
10
~
DB1
1
0
3
-
~
Ring signal
detection
circuit
Active
O
H
Line 1 Dial Pulse Generation Signal
FAX board
3
3
Q51
AG
+
+5V
4
1
PC1
3
2
4
4
Q53
SG
Fig. 4-6
Description
© 2006 - 2008 TOSHIBA TEC CORPORATION All rights reserved
4 - 6
MAIN board
CML1
27
27
144
LD1
61
61
143
Destination
Q53
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