Light test (CB8789E)

This light-sensing probe was found in a 90s Popular Electronics. The circuit detects light sources by triggering a buzzer.

Car Battery Checker (CB9529E)
We found this circuit in an American documentation from the 90s. Through an LED it indicates the...
ADuM120N and 121N Two Channel Digital Isolators (COM065E)
August 2016 - It can be purchased from Mouser Electronics the new digital isolators ADuM120N and...
TTL Active Cycle Control (CB13825E)
In this circuit, from a documentation from the 70's, we have the way to control the active cycle of...