Neon sign

In the signage industry, neon signs are electric signs lighted by long luminous gas-discharge tubes that contain rarefied neon or other gases. They are the most common use for neon lighting, which was first demonstrated in a modern form in December 1910 by Georges Claude at the Paris Motor Show. While they are used worldwide, neon signs were popular in the United States from about the 1920s to 1950s. The installations in Times Square, many originally designed by Douglas Leigh, were famed, and there were nearly 2,000 small shops producing neon signs by 1940. In addition to signage, neon lighting is used frequently by artists and architects, and (in a modified form) in plasma display panels and televisions. The signage industry has declined in the past several decades, and cities are now concerned with preserving and restoring their antique neon signs. Light emitting diode arrays can be formed to simulate the appearance of neon lamps. The neon sign is an evolution of the earlier Geissler tube, which is a sealed glass tube containing a "rarefied" gas (the gas pressure in the tube is well below atmospheric pressure). When a voltage is applied to electrodes inserted through the glass, an electrical glow discharge results. Geissler tubes were popular in the late 19th century, and the different colors they emitted were characteristics of the gases within. They were unsuitable for general lighting, as the pressure of the gas inside typically declined with use. The direct predecessor of neon tube lighting was the Moore tube, which used nitrogen or carbon dioxide as the luminous gas and a patented mechanism for maintaining pressure. Moore tubes were sold for commercial lighting for a number of years in the early 1900s. The discovery of neon in 1898 by British scientists William Ramsay and Morris W. Travers included the observation of a brilliant red glow in Geissler tubes. Travers wrote, "the blaze of crimson light from the tube told its own story and was a sight to dwell upon and never forget.