We obtained this circuit in a technical documentation from the 90's. The circuit has its sensitivity adjustment in the potentiometer. The supply voltage can be reduced with a 1k resistor change.
This circuit has a low level at its output (pin 8) when the input signal has a frequency of 10...
Found in a 1993 Electronics Experimenter Handbook, this circuit uses a multimeter to measure...
The circuit is from an old American publication. We can mount it with the BC548 and TIP31. The...