This circuit is from 1967 General Electric documentation. It uses SUS which are not very common components today. The maximum frequency should not exceed a few kilohertz.
In fact, this 1994 circuit uses a scale of LEDs to indicate the pulse rate applied to its input....
We found this circuit, which is actually a window discriminator, in the 1991 Electronics...
This circuit acts on the dynamic range of an audio signal, which can be useful for recording,...