This synthesis will be of interest to traffic engineers and others interested in the capabilities of currently available equipment for traffic signal control. Information is provided on functions and operations of controller assemblies, displays, detectors, communications, and computerized system masters. Traffic engineers need to know the functional capabilities of the various types of signal control equipment in order to select appropriate equipment for a specific application. This report of the Transportation Research Board describes the functions of each type of equipment and how it works, and gives advantages, disadvantages, and limitations.