Published in a PE Hobbyst Handbook of 1991, this sensor uses an integrated circuit that is unusual today. The circuit is based on a high frequency oscillator.
Using the 2N2646 this circuit was found in a Radio Electronics magazine from July 1968. The...
The purpose of this circuit found in a 1990s Popular Electronics is to increase the current...
Found a documentation for PC from 1992, this circuit is indicated for the English power grid of...