Electromechanical Counter (CB21682E)

This photoelectric circuit from a 1960 publication uses a 6.3 V electromechanical counter, common at the time.

Simple Relay Shield (CB21223E)
This circuit was found in old American documentation. Transistor is general purpose and relay is...
Simple Alarm (CB25944E)
This simple alarm with latching uses a relay as the main element. The circuit is from a Radio...
Telephone Pickup (CB12308E)
This circuit is from an Italian publication called Fare Elettronica from 1987. What we have is an...