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 circuit is from European documentation from the 1980s. The circuit consists of an R-S...
Found in the documentation on PCs, this circuit excites LEDs whose current is determined by R3....
This simple SCR relaxation oscillator was indicated by a 90s Popular Electronics. The frequency is...