This circuit was found in a Popular Electronics of the 1990s. The sensor is a rotating mechanical system with a propeller-driven magnet to count pulses with a reedswitch.
This circuit was found in a 1995 documentation, consisting of a car protection system that blocks...
Found in a 1960 Gernsback documentation, this circuit triggers an electromechanical counter of the...
We found this circuit in an old Radio Electronics. The transistors can be the BC548. The circuit...