This circuit from a Popular Electronics from the 90s uses a common optocoupler and a general-purpose transistor to control a sensitive relay that can be from 6 to 12 V.
This voltage-controlled oscillator with two operational amplifiers and a transistor that can be...
This 1986 documentation circuit provides 3, 4, 5, 6 V voltages under 350 mA for powering walkmans...
This circuit was obtained from an American publication from the 60's. The transistors are...