This oscillator that generates signals below the audible range (sub audio or infrasound) was found in a 1965 documentation. Transistors are for general use.
Found in a 90s Popular Electronics, this circuit excites a 40 kHz ultrasonic transducer. The...
This circuit was suggested by Electronic Engineering in a 1980s publication. The circuit makes use...
In this circuit R1 is 56 ohm and R2 is 220 ohm for the 110 V network. SCRs are according to the...