Found in a 1965 CQ magazine, this circuit uses period components. The unijunction transistor can be a 2N2646 and the relay has voltage according to the supply.
This circuit is from 1990 documentation. It uses a bridge with LEDs and the potentiometer must be...
This circuit has the spark duration controlled by a 555 timer. The circuit was found in the 1990...
Taking Raytheon's 3900 integrated circuits as an example, uncommon today, this circuit can be used...