This SCR relaxation oscillator was found in an 80's Electronic Design. It flashes a small incandescent lamp in frequency that depends on the capacitor.
This circuit was found in an EDN from the 90s. For the components indicated, the frequency is 10 kHz....
This circuit simulates the signal produced by a muscle, serving to adjust medical equipment. The circuit...
This circuit generates a 1.46 kHz sine wave with an output ranging less than 1.5% in frequency...