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.
The basis of this circuit is a CA3130 operational amplifier. The transistor can be BC548, and the...
This circuit, found in a 73 magazine for radio amateurs, is used in radio localization. The...
This circuit is from an American magazine Popular Electronics of March 1991. The circuit produces both...