The advantages that can be obtained from using a ternary or higher-order system are enumerated. The various techniques using semiconductor, devices are described with particular reference to the ternary system, and the circuits that have been developed from these techniques are reviewed. The prototype circuits described in the paper have been developed primarily to show the feasibility of a ternary computer or data-processing equipment, and it is expected that further engineering design will be needed to construct a large higher-speed machine. The main types of logic are surveyed, and the principal operators required to mechanize a system are discussed.