Sine-wave speech can be thought of as a sort of auditory illusion, a sensory edge case in which one’s experience has a clear “before” and “after” moment, like going through a one-way door.

However, the 28.8 MHz oscillator onboard isn’t as stable ... The Fourier series tells you that a square wave is an infinite sum of sine waves. One sine wave is at the fundamental frequency ...

Part 1 shows how to make an oscillator with a pitch that is proportional to a control voltage. Part 2 shows how to modify the circuit for use with higher supply voltages, implement it using discrete ...