We found this circuit in the September 1992 issue of Radio Electronics magazine. It can be triggered by any signal above ½ Vcc, where Vcc is the supply voltage.
This circuit was obtained in an Electronics World of 1969. It is a crystal oscillator with a 100...
This circuit, shown in the figure, consists of a variable gain amplifier with differential input...
This circuit was found in the July 1992 Radio Electronics magazine. Sensitivity adjustment is made...