Astatic formed CAD Professional Microphones in 1988 as a division of Astatic. It is characterized by the development of myoclonic seizures and/or myoclonic astatic seizures. In 1825 he developed the astatic galvanometer. The commercial audio product division of Astatic became CAD Professional Microphones in 1988. The original Astatic model JT-30 was introduced in late 1939. The Blues Blaster elements were Astatic MC-151 Crystal elements until 2001. Because of this phenomenon, astatic needles were often used in galvanometers. The Astatic Corporation is a commercial audio products manufacturer founded in Youngstown, Ohio in 1933. An astatic system comprises two equal and parallel magnetic needles, but with their polarities reversed. DAS expanded the Astatic name to non-microphone accessories including coaxial cables, meters and antennas. Astatic also manufactured bullet style microphones, which are extremely popular among harmonica players.