Thomas Edison of the Edison patent to charge a more reasonable rate for the use of the Edison patent rights and lowering the price of the electric lamp. On October 8, 1883, the US patent office ruled that Edison's patent was based on the work of William E. Sawyer and was, therefore, invalid. Litigation continued for nearly six years, until October 6, 1889, when a judge ruled that Edison's electric light improvement claim for "a filament of carbon of high resistance" was valid. To avoid a possible court battle with Joseph Swan, whose British patent had been awarded a year before Edison's,
Bi-pin lamp base These are sometimes called "mini-bipin". Where the terminals of the lamp are bent back onto the sides of the base of the bulb, this forms a wedge base, often used in small bulbs for automotive lighting. The bi-pin base was invented by Reginald Fessenden for the 1893 World's Fair in Chicago. After Westinghouse won the contract to wire and illuminate the first electrified fair with AC instead of arch-rival Thomas Edison's DC, Edison and his General Electric company refused to allow his patented Edison screw-base bulbs to be used. Westinghouse overcame this by developing the bi-pin base for use at