6000 Megacycle/Sec Radio Relay System for Broad-band, long Haul Service in the Bell System.

DEVELOPMENT of microwave communication facilities for Bell System use was undertaken in 1945, taking advantage of prewar research at Bell Telephone Laboratories and of the impetus in technology achieved during the war years. In 1947, an experimental 4,000-mc/sec (megacycle per second) system of moderate bandwidth (TD-X)1 was established between New York, N. Y., and Boston, Mass., a route distance of approximately 220 miles (354 kilometers). It was used commercially for transmission of television signals and experimentally for telephone transmission.