New Concepts in Exchange Outside Plant Engineering

Since World War II there have been major changes in exchange outside plant cable networks. Polyethylene has replaced lead for cable sheaths, and in the distribution plant, polyethylene insulated conductor 373 374 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1965 cable (PIC) and rcady-access terminals have replaced paper insulated cable and sealed terminals. Concentrator and carrier systems permit more efficient use of copper in feeder and trunk cables. In the early stages of these wide-sweeping changes, the major advances were in hardware, as enumerated above; however, exchange plant engineering methods were being analyzed and revised to take full advantage of these innovations. The P I C cable and ready-access terminals had implications on exchange plant installation and maintenance much broader than the purely hardware ones. For instance, the installation of distribution terminals for access to the cable conductors could be postponed economically until required to satisfy a request for service. Concurrently, unrelated activities were producing results applicable to the plant engineer's problem. Operations research techniques (which aim to optimize an existing system) were being used. More sophisticated electronic computers became available and provided the tools of calculations and machine decision logic on a scale impossible in the past. All of these factors sparked a revolution in the tools and methods used by the engineer to study and evaluate the exchange outside plant as a system, with t he ultimate objective of improved service for customers.