Style "B" semaphore, the first successful low voltage, entirely enclosed mechanism electric motor semaphore appeared. It was revolutionary, improving on all earlier semaphore designs, with the last such example being taken out of service as recently as 2009 on the former Siskiyou line of the S.P., now CORPS. The motor-controlled North American semaphores used since the advent of the track circuit block system of 1872, provided a form of automation sought after by the railroads to reduce labor costs and improve reliability over manually operated systems as in the UK, Germany and elsewhere. Dwarf signals were worked mechanically, pneumatically to give restricting-type signals as did mast type signals at interlockings, but motorized dwarfs were more common after the development of the Model 2A signal in 1908. As early as 1915, the technological push by -such intellectual giants as A.H. Rudd of the Pennsylvania R.R. and his concept of speed signaling combined with his development of the Position Light signal and the concurrent color-light signals using William Churchill's doublet lens combination in practical terms made the semaphore technically obsolete. Semaphore signals have been almost completely replaced by light signals in North America, but they contain several important design elements. The overwhelming majority of semaphore type signals used in North America, and the only type surviving in service as of 2009 are of the three position, upper quadrant variety. Those of the lower quadrant variety would most often have two positions, but three roundels, with two being of the more restrictive color. This 60-75 degree lower quadrant, three aperture design of semaphore spectacle was known as the "Continuous Light Spectacle" and predates the Loree-Patenall patented, three position upper quadrant spectacle of 1902. The intent was to reduce the chance of a malfunction or snowfall causing the signal to only partially rise towards the horizontal, yet still displaying the most restrictive color night indication. Color images of these signals bear this out as the "Red-Red-Green" of the home and "Yellow-Yellow-Green" of the distant arms were universal used on 60 and 75 degree (B&M, Central Vermont) L.Q. semaphores. There were no three color 60 or 75 degree signals used. The "standard" 90 degree 3 position Lower Quadrant spectacle saw limited application (the last were used in Memphis, Tenn. and St. Louis, Mo,. Terminals) as the Lorre-Patenall U.Q. spectacle provided significantly greater visual range. The blade portion of the semaphore was of several designs, each