This battery-powered 3-valve circuit was found in American documentation from 1947; Two batteries are used, one high voltage and one low voltage for the filaments.
We found this circuit in a 1977 Radio Shack brochure. Transistors can be the most modern BC548 for NPN...
This application is from a circuit manual from the 90s and only works with incandescent lamps. The triac...
This more sophisticated version compared to the previous one in this section was also found in 90s...