This circuit from a Popular Electronics from the 90's can generate signals from 0.03 Hz to 3 kHz depending on the value of the capacitor and resistor.
The frequency of the produced sound depends on the capacitor. With capacitors of known values, you can...
In this circuit, from a 1977 publication, we have the traditional version of a filter that rejects 1...
A VCO or VCF [Voltage to Frequency Converter] can be built using part of a 4048 [PLL] circuit. The...