Toshiba DP120F Service Manual page 395

EU/AU/ASIA/HK models
07-4-04E
Fig. 7-4-10
The CI detect circuit consists of the photo-coupler (PC1), I/OP-1 GA (IC7) on the Main PBA,
and other peripheral devices to detect a ring signal input from the telephone line.
The I/OP-1 GA causes the CML1 signal to be LOW to connect the CI detection circuit to the
line. When a ring signal is input from the telephone line, the photo-coupler repeats turning on
and off. This allows Q5 to turn on and off and the OCI1 signal to be a pulse signal and input to
the I/OP-1 GA on the Main PBA, thereby detecting the ring signal.
Signal Name Type Active Description Destination
OCI1 I - Line 1 CI Detect Signal I/OP-1 GA
DP120F/DP125F Circuit Description 7-86 March 2000 © TOSHIBA TEC