This shield circuit is from a 1968s Motorola documentation. The relay is according to the supply voltage. R1 can be reduced to lower trigger voltages.
This circuit was found in the 1972 RCA Power Transistor Databook. Transistors are uncommon today,...
This circuit is used to light a 20 W fluorescent lamp from the 12 V of a car battery. The...
This circuit fires by burning the fuse when the input voltage exceeds the value referenced by the zener....