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,
Joseph Swan This required a wired supply, so the following year, he presented one with a battery and other improved versions followed. By 1886, a lamp with better light output than a flame safety lamp was in production by the Edison-Swan Company. However, it suffered from problems of reliability and was not a success. It took development by others over the next 20 years or so before effective electric lamps were in common use. In what are considered to be independent lines of inquiry, Swan's incandescent electric lamp was developed at the same time Thomas Edison was working on his incandescent lamp