This optical coupler for short distances is powered by 12 V which is the voltage of the lamp and the relay. The circuit can also use emitting LEDs and the phototransistor can be of any type.
This car turn signal circuit was found in the April 1969 issue of Radio Electronics magazine. The...
We found this circuit in a documentation about SCRs from the 70s. The circuit can be implemented with a...
This circuit was found in a 1998 documentation and its purpose is to automate controls by timing its...