The TL Radio Relay System

In the past, short-haul microwave radio relay development in the Bell System has progressed along the general lines of heavy-route, cross2297 2298 THE BELL SYSTEM TECHNICAL JOURNAL, S E P T E M B E R 1963 country systems. T h e use of high towers on substantial plots of land located on prominent sites often requiring expensive access roads and power lines was typical. Buildings were sufficiently large to accommodate not only a large number of radio equipment bays b u t also 5- to 10-kilow a t t rotating machinery to provide backup in the event of power failure. Radio equipment costs seldom approached one-half of the total costs of such repeaters. Today, ideas originally proposed by the Radio Research D e p a r t m e n t of Bell Telephone Laboratories to reduce over-all microwave station costs have become a reality. 1 T h e TL radio relay is a new microwave system designed specifically for short-haul service. Low equipment costs, minimum engineering and installation effort, outdoor housing, low-cost a n t e n n a support structures, small power consumption, and moderate telephone circuit capacity all contribute to substantially lower over-all TL radio station costs. A high degree of reliability is provided by extensive use of solid-state circuitry, float-charged reserve b a t t e r y power supply system, and simplified maintenance procedures.