This circuit was found in a 1967 Electronics World. Transistor Q1 can be a TIP321 and Q2 can be a BC558. The indicator lamp is optional.
This circuit can be used for several purposes such as pulse counter, pass counter, roulette, etc....
This circuit is from Radio Electronics. The magazine no more exists, but the circuit can be...
We found this circuit in a French documentation from the 80's. The components used are still...