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The history of traffic signals is traced from the signal fires which guided early man to the sophisticated electromechanical signal devices of today. Early experiments with officer-operated semaphores, lanterns, and electric lights are discussed. The influence of railroad signaling is noted, as are the innovative efforts of inventors who saw the problems of congestion and hazard developing to the point where control measures were essential. Descriptions of several devices show the imagination of early practitioners, and one may reflect with some humor on what might have been developed for use today. Some of the earliest attempts at automatic control even made use of the policeman's whistle, blown by a small compressor, while later efforts included clanging bells as a substitute. The extent to which some of these quite primitive devices survived in actual use into the post-World War II era is remarkable; devices unique to an area often hung on, long beyond the time when they were made obsolete by newer devices. Credit is given to several pioneers in the field, along with appropriate references to the few who have contributed to preservation of parts of the history of this interesting subject.