This circuit was found in an Electronic World of 1968. The circuit uses power transistors of the time. The transistors are for 25 W of dissipation.
This excellent amplifier, found in a 1986 documentation, provides good power and is powered by a...
This circuit needs only 0.7 V at 40 uA to drive the relay. We found it in the November 1993...
Instead of LED bulbs, LEDs with a series 470 ohm 1k resistor can be used in this 80's circuit....