This circuit was found in General Electric documentation from 1965. The transistors are from that time. The diodes consist of a component that contained them.
This circuit that can amplify signals from 0 to 30 MHz was found in a 90s Popular Electronics....
This circuit makes use of a low impedance microphone. The relay is according to the supply voltage...
This circuit for incandescent lamps was found in a 70s documentation. The circuit uses an SCR...