DC, or direct current, is among the earliest experiments in electric current. Its first commercial use was by Thomas Edison, renown inventor of the light bulb. Edison found direct current to be unreliable over long distances, however. Tremendous amounts of voltage had to be produced to get the direct current to travel. It was soon abandoned in favor of AC, or alternating current. The primary difference between the two types of electricity is direct current goes in one direction only, where alternating current whips back and forth, similar to a sine-wave, giving it more distance to travel. The first name mentioned with alternating current was Guillame Duchenne, who also developed electrotherapy. Other names mentioned in the development of alternating current are Lucien Gulgard, John Dixon Gibbs, and Nikola Tesla. George Westinghouse bought the rights on Teslas alternating current technology to be used in his Westinghouse Electric Corporation.