L5 System: Overall Description and System Design

During the last 30 years, long-haul transmission facilities have been rapidly expanded to meet the increasing need for both voice and data transmission, and it is expected that rapid growth will continue in the 1970's although possibly at a slower rate than the 15 percent per year which typified the late 1960's. Thus, during this period there has continued to be a need for new systems providing increased message capacity at lower cost to supplement the systems already available in the long-haul plant. As can be seen in Table I, the L5 Coaxial-Carrier Transmission System is the latest in a family of coaxial transmission systems developed to date.* It is evident that the newer coaxial systems have achieved increased capacity because of better utilization of the transmission medium (i.e., * The sheath capacities listed in Table I are the ones most commonly associated with each of the systems. The initial L3 application, in 1953, was actually on Coax-8 (i.e., a cable which includes eight coaxials) with a total sheath capacity of 5580 circuits on three working pairs, with one pair reserved for protection. 1901