This circuit generates signals in four frequency bands with the threshold values indicated in the diagram. The circuit was found in the March 1996 issue of Electronics Now magazine.
This oscillator with crystal for overtone operation was found in an old American documentation. The coil...
In the figure we have a basic PLL circuit with the LM567 or equivalent. The circuit is from a 1977...
The A3906 integrated circuit from Allegro MicroSystems (www.allegro.com) consists of a single...