L5 System: Physical Design

Physical Design By R. J. WIRTZ and W. G. ALBERT (Manuscript received April 5, 1974) The L5 Coaxial-Carrier Transmission System equipment was designed to -provide long-term reliable service in diverse environments. The line repeaters, for instance, are housed in apparatus cases located in manholes that are subjected to flooding, whereas the main-station repeaters and terminal multiplexing equipment are located in the controlled environment of underground or aboveground buildings, often only partially attended by maintenance personnel. In addition to describing novel physical designs, this paper covers other very important considerations such as thermal design, manufacturability, incorporation of hybrid integrated-circuit technology, efficient ''building-block" system growth capability, and longterm reliability. I. INTRODUCTION 1.1 Outside plant design considerations Proposed approaches to the physical design of L5 repeaters covered a wide array of possibilities ranging from the buried repeater concept to that of an ideal conversion. The former would capitalize on the high reliability and trouble-free performance of solid-state repeaters to gain cost advantages in outside plant for new routes, but would require initially equipping all tubes of a coaxial cable with repeaters. The latter approach would feature repeaters configured to closely resemble existing L4 system repeaters.1 It would encourage conversions from the L4 to the L5 system and take advantage of as much existing outside plant as possible.