The Evolution and Special Features of Bell System Telephone Equipment Buildings

Telephone company equipment buildings, known generically as wire centers, central offices, and transmission stations, are geographically placed and specifically designed and constructed to function as effective parts of the nationwide telephone network. As a result, the planning of such facilities requires different considerations than those found in conventional architectural and building design activities. The basic purpose of a telephone equipment facility, and therefore the primary objective in its design, is to provide the appropriate assembly of equipment, cable, wire, and control, operation, and support systems within a protective enclosure to satisfy the needs for local and nationwide telephone service. The enclosure, equipment, and circuits are so tightly interrelated that they are commonly identified as an equipment-building system. 427 This paper describes the various classes of telephone equipment buildings in the Bell System and the evolution of the design standards for the modern central office and transmission station. The sequence of events that occur in the planning and construction of a new equipment building is presented and is followed by information about the special design and construction of the electrical, mechanical, and structural portions of central offices and transmission stations.