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.
Vishay's VCNL4200 integrated circuit consists of a fully integrated proximity detector containing...
This circuit samples the current in a load and in case of excessive value it activates a...
The frequency of this oscillator depends on the crystal used and the transistors. The circuit was...