Toshiba DP120F, Service Manual

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March 2000 © TOSHIBA TEC 7-85 DP120F/DP125F Circuit Description
4.4 CI Detect Circuit
US/CA/TW models
The CI detect circuit consists of the photo-coupler (PC2), 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
telephone line. When a ring signal is input from the telephone line, the photo-coupler repeats
turning on and off. This allows 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.
Fig. 7-4-9
07-04-04
Signal Name Type Active Description Destination
OCI1 I - Line 1 CI Detect Signal I/OP-1 GA