Found in a 90s Popular Electronics, this circuit uses a 741 to generate frequencies from 0.1 to 30 Hz. Observe the phototransistor feedback.
This circuit was obtained in the publication 101 Electronics Projects of 1979. The circuit can be...
If you have an old cassette player or bought one from a junk shop, you can set up a small table...
This circuit was found in a 70s American documentation. The converter can be of any type and the...