In the figure we have 3 oscillators with logic gates that can be triggered by external logic signals. The circuits were found in the Radio Electronics magazine of April 1987.
Based on FET operational amplifiers, this circuit was found in a manufactirer documentation. The...
This circuit, obtained from a 1965 magazine, can still be assembled using some modern equivalent...
This circuit uses an operational amplifier that is still common today. The indication is made by...