This variable frequency circuit was found in a Popular Electronics from the 90s. The circuit outputs to a small speaker and can be powered by voltages as low as 3 V.
Found in a 90s Radio Electronics, this circuit is intended to drive a neon lamp from a 9 V source....
This simple tester was found in a Popular Electronics from the 90s. The circuit is powered by two...
Electronics Now from the 90's suggests this pulse conditioner circuit for use in tachometers. The...