This circuit was obtained from an Electronic Design from the 90's. The circuit generates signals at a frequency determined by R and C. The selection by the jumpers determines the PWM modulation.
This traditional rectangular oscillator configuration generates signals up to a few megahertz...
This circuit is just a curiosity found in a 1990 documentation, since the integrated circuit used...
This circuit goes into operation producing a sound on a small speaker when the supply voltage...