Found in a 90’s American documentation, this circuit indicates the frequency of input pulses up to 1 kHz. The circuit has a very explored configuration on this site.
This is a possible setting for a Colpitts oscillator operating in the audio track. The shunt coil...
With this circuit, three LEDs of different colors can be controlled sequentially. Adjustments of...
We found this circuit in an old English publication. The resistor not indicated can be 2k2 and the...