We found this circuit in an article in Radio Electronics magazine from November 1971. The circuit has several sensor inputs and is based on programmable unijunction transistors or PUTs.
Found in Popular Electronics from the 90s, this circuit can employ other low power audio...
This blocking oscillator that appears elsewhere on this site from other sources, was found in a...
This mixer configuration from a 1967 publication can be adapted to work with modern transistors. The...