This circuit was obtained in a Popular Electronics of the 90s. The circuit is compatible with microcontrollers being powered by 5 V.
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...