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,
Signal lamp lamps are still used today, as a backup device in case of a complete failure of an aircraft's radio. Light signals can be green, red, or white, and steady or flashing. Messages are limited to a handful of basic instructions (e.g., "land", "stop", etc.); they are not intended to be used for transmitting messages in Morse code. Aircraft can acknowledge signals by rocking their wings or flashing their landing lights. Signal lamp A signal lamp (sometimes called an Aldis lamp, after Arthur Cyril Webb Aldis who invented a widely used design, or a Morse lamp) is a visual signaling device