Using neon lamps, this circuit from a 1969 publication provides 17 V of maximum voltage or else adjustable.
We found this circuit in an 80's Radio Electronics. The circuit uses a PTC sensor and an LED...
In this circuit a 12 V lamp or LED blinks with the music signal applied to the input. R depends on...
Using a period sensor, this circuit was found in the February 1986 issue of Radio Electronics...