We found this circuit in an Australian publication from 1991. It is a kit of the time with input for a guitar pickup. The range is a few tens of meters.
This circuit found in a European publication from the 1980s, is based on PLL 566. The frequencies...
The circuit shown, with the printed circuit board, was found in an article in the June 1990 issue...
In the figure we have a simple timer with two voltage comparators of the four of an LM339. The...