Found in a Popular Electronics from the 90's, this circuit can generate frequencies according to the values of the employed components, according to the table next to the diagram.
This commercial receiver from the year 1958 uses two AA cells as Power supply. The circuit is...
PIC18F “K40” Features Intelligent ADC with Filtering and Signal Analysis Capabilities Ideal for...
This circuit appears in similar versions on this site. This is from a Popular Electronics from the 80's. The...