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.
The integrated circuit used is a version close to the 555 manufactured by Motorola. The circuit shown...
The circuit shown is from an American publication from 1970. It produces a tone that attracts fish...
Suggested by General Electric documentation from 1968, this circuit activates a relay after 60...