Dial Pulse Generation Circuit - Toshiba GD-1210 Service Manual

4.2.3

Dial pulse generation circuit

NA/TW models
NCU board
C5
RLY2
+12V
CML relay
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
(IC29 [IC26]) on the FAX 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 O
* Values in [ ] are for GD-1250/1270 in case that the descriptions vary between GD-1210 and GD-
1250/1270.
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R4
12
1 8
0 10
~
DB1
1
0 3 - +
4
~
3
Ring signal
detection
circuit
Fig. 4-7
Active
H Line 1 Dial Pulse Generation Signal
4 - 7
08/04
FAX board
3 3
Q51
AG
+5V
1
PC1
2
4 4
Q53
SG
Description
CML1 21
IC29
[ IC26 ]
ASIC
LD1 20
Destination
Q53
GD-1210/1250/1270/1160/1260
ELECTRICAL CIRCUITS
4