indication greater visual range than obtained with the use of a single lamp unit. Searchlight signals are typically mounted with a large circular background, with one or two railroads preferring a small target, such as the New York Central beginning in the mid late 1950s under the Perlman administration. Triangular color light signals Triangularly arranged color light signals consist of a cluster of three color lamp sockets in the middle of a large circular target. They were one of the first widely used type of high intensity color light signal, notably adopted by the New York Central and Seaboard Coast Line railroads, and later used exclusively by Conrail and New Jersey Transit. The original General Railway Signal (GRS) Type "G" design consisted of a cast iron box containing three doublet lens units in a triangular arrangement. The US&S "TR" and "TP" models used three smaller connected single lamp housings with a common background. The long defunct Chicago Signal Company had a version that used standard 5-3/8" switch lamp lenses (often of Macbeth manufacture) instead of the otherwise standard inverse-convex and stepped lens type found in the standard inner doublet design. The Union version was later updated to a single unit akin to the GRS model. As modular color light signals have become widespread, target-type configurations have been typically offered alongside vertical type configurations. The triangular color light signal was especially useful in physically restricted and confined areas. Vertical color light signals Vertical color light signals are the second major pattern of color light signals, and today represent the most popular form of signal in North America, supplanting the searchlight. These signals are not different from the triangular type color signal in function, but present a much altered visual appearance. Continuing problems with reliable, long range light sources from a single, optical colored lens and a focused bulb restricted the first use of color light signals to short range daytime exterior applications, or tunnels and other underground or low speed complexes. The 1911 New York Penn Station project was one example of this type of color light signal, with an outer colored 8 3/8" optical lens, some of which are still in service as of 2011. Development of the doublet lens by Churchill at Corning Glass Works allowed an electric light source to be more effective than with previous daytime colorlight signal designs. There are two main types of cases: the