Loop Plant Electronics: Physical Design Considerations

Although electronics technology has been used for many years in the central offices and toll plant of the Bell System, its use in the loop plant is in its infancy. The first Western Electric loop electronic range-extension product, the 2A, was installed in central offices in 1968. Since that time, a complete family of loop electronic products has been developed, and its introduction has generated new challenges for physical design. 1185 Unlike most Bell System electronic systems, certain elements of loop electronics hardware must be designed to mount outdoors (commonly referred to as the "outside plant") as well as in the central office. The central office is generally a controlled environment and is largely standardized from a facilities and craft point of view. The outside plant environment, on the other hand, has more variety in facilities including aerial, underground, and buried plant; a multiplicity of cable and cable apparatus with which the electronics must interconnect; and large variety in crafts: splicers, installers, linepersons, and repairpersons. The aim of this paper is to highlight the central office and outside plant physical design of loop electronics products currently being manufactured by the Western Electric Company, Incorporated. The loop electronics product line is diverse. Small carrier and voice frequency systems and large carrier and concentrator systems must be economically and ruggedly designed and packaged. Typically, the volume occupied at a remote terminal site varies from 135 cubic inches for a single channel analog carrier system to 16 cubic feet for a 40-channel digital carrier system.