the signal in broad daylight, when the signal was located on tangent track. The early color light signals were visible for only about half that distance (2,500 feet) while using about the same current consumption, then a major concern in "Primary Battery Territory." By 1925, the development of "High Transmission Colors" of railroad glassware by Dr. Gage and Corning Glass improved this limited distance to an acceptably competitive 3,500 feet on tangent track. When the new Hall Searchlight signals were introduced in 1920, the recorded response by many engineman was classic: "They took the old 'Hall Banjo Signal,' resurrected it from the grave and lighted it up!" In the UK, original electromechanical searchlight signals consisted of a low wattage incandescent bulb mounted behind a semaphore spectacle devoid of a blade behind a target. The Union Switch and Signal Company searchlight signal ubiquitous to the United States has an internal cable with weights system to mechanically align the signal in the red position if there is a system failure. Searchlight signal's use became widespread mostly due to their relatively low maintenance, high visibility, low power-consumption, and after 1932 using a compound lens with a 4 watt, 3 volt bulb, that worked quite well in territory with battery powered signaling. Also of significance was the single lens giving the indications in multiple head interlocking signals in a fixed location with regard to the mast and the other signal heads, this not being the case with multiple lenses color light signals. In time the costs of the significantly more expensive searchlight signal's relay began to outweigh the savings from its compact size and single bulb when compared with the simple multiple lensed color light signal. By the end of the 1980s the searchlight had lost its position as the most popular signal style in North America. To overcome the issues of associated with moving parts, new solid state, single-lensed signals have been developed. The first such product, marketed in 1968 as the "Unilens" by Safetran, uses fiber optics to concentrate the output of up to four light sources behind a single lens. However, other than as low speed signals requiring only short range visibility, these have not been entirely successful and most are now being removed from mainline service after a relatively short working life. Capable of four aspects, most examples had two lamp units simultaneously light red to give the most restrictive