Circuit diagram of telephone call counter

Photocoupler

Telephone Call Counter This circuit pushes the solenoid diagram, which releases the R\S counter key of the SR-56 calculator for each inquiry event. The interrogation event is formed by a burst of pulses corresponding to each ring. The wave group is separated by 4s, so the line includes a delay, which is to prevent the solenoid from being driven when the guiding telephone line is still kept more than 5s after being queried.