This 1967 modeling circuit mimics the whistle of a locomotive. The steam-shrieking wheezing is set in a 2k2 potentiometer.
This S-meter circuit was found in a 1976 publication. The circuit is used to measure the signal...
Several versions of this circuit can be found on this website. This makes use of FETs that can...
With the circuit shown in the figure we have a frequency modulation which is produced by a...