The frequency of each note depends on R2, which must be replaced by a keyboard. The circuit is from Radio Electronics from April 1980. The power supply is 9 V for the amplifier used.
With the change of the coil, the circuit can operate at frequencies between 30 MHz and 150 MHz....
The frequency of this Pierce oscillator, found in 1969 documentation, depends on the crystal. The...
This simple circuit can be used to power a simple communication system using ordinary telephones....