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.
This simple multitester tests continuity, semiconductors, leaks, and other common component...
This configuration can be implemented with equivalent operations. The circuit is from the 1990...
This circuit is one of many that we have in our section. It was taken from the Electronics...