Based on TTL logic this circuit can vary both the frequency and the pulse width of a rectangular signal. Equivalent components can be tested.
We found this CMOS circuit in a 1978 publication. It allows you to use a standard calculator...
In the figure we have an oscillator for microcontrollers capable of operating in the frequencies of 10,...
This fast Schmitt trigger operates at frequencies from 10 Hz to 100 Hz, with very short rise time....