This circuit was found in the January 1996 issue of Electronics Now magazine. The circuit is powered by voltages from 10 to 24 V and has a control for the intensity of the output signal.
We have dozens of similar projects in articles and circuits on this site. This is from Radio...
This circuit with an unusual configuration was found in the January 1974 issue of Radio...
This interesting circuit from 1967 documentation uses three series lamps to regulate the voltage...