This circuit was found in a 1993 Electronics Hobbyst Handbook. The circuit operates in the FM range. The coil has 4 turns of 24 or 26 wire in a coreless form 0.5 cm diameter.
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...