Found in old documentation, this circuit makes use of amplifiers of the time, uncommon today. Next to the diagram, the formula for calculating the components.
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...