Found in Popular Electronics from the 90s, this circuit is based on a PLL567 and employs high-end or ultrasonic speakers depending on the frequency of oscillations.
This circuit uses in operational amplifier to produce square and triangular low frequency signals....
Found in a 1968 American documentation, this circuit generates sawtooth signals whose rise and...
This VCA was found in the July 1988 issue of Radio Electronics magazine. It uses an OTA op amp and...