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The object of this traffic controller is to keep the signal green on the major street, and to give the green signal to the minor street only when requested. The minor street vehicle can always get the green signal after a short wait, while the major street receives green light for as much extra time as the minor street traffic permits. Two experimental horizontal beam installations, which accomplish the above object, are now in operation in Wilkinsburg, Pennsylvania. The focussed light beam, phototube unit, relay panels, and associated circuits are described in this paper.