Dial Pulse Generation Circuit - Toshiba DP120F Service Manual

4.2 Dial Pulse Generation Circuit

US/CA/TW models
07-04-02
Fig. 7-4-5
The dial pulse generation circuit consists of the diode bridge (DB1), photo-coupler (PC1), the I/
OP-1 GA (IC7) on the Main PBA, and other peripheral devices. It generates dial pulses in
facsimile transmission and dialing outside.
The I/OP-1 GA causes the CML1 signal to be HIGH to connect the line to the MODEM side. To
achieve a dial make, the I/OP-1 GA causes the LD1 signal to be HIGH to turn on Q53. This
allows the photo-coupler to turn on and allow current to flow through the diode bridge for send-
ing dial pulses to the line.
Signal Name Type Active Description Destination
LD1 O H Line 1 Dial Pulse Generate Signal Q53
March 2000 © TOSHIBA TEC 7-81 DP120F/DP125F Circuit Description