Some Recent Developments in Long Distance Cables in the United States of America
01 July 1930
of distance circuits, particularly THE transmission history onelongcontinual reductionandcircuit costs. long distance cable circuits, has been one of continually improving standards. It has also been of of These have resulted largely from new developments to which have been added economies resulting from heavy growth and improved engineering. To put it another way, present-day circuits are capable of transmitting a kilocycle of frequency range more cheaply than those of earlier days. As the cost per kilocycle of band width has been reduced, part of the cost reduction has naturally been used in furnishing telephone customers wider-band and generally better telephone circuits. The accompanying chart is of interest in comparing the transmission frequency characteristics of what were considered good telephone circuits some time ago with what are considered good telephone circuits today and what are proposed for the future. At the left of the chart are shown various types of circuits which have been in use or proposed for New York-San Francisco service, a distance of a little over 3,000 miles. The original loaded transcontinental line, which remained in service from January 25, 1915, until April, 1920, when it was unloaded, gave a band width of only about 900 cycles.* The non-loaded circuit was better, giving about 1,800 cycles. The modern carrier telephone circuit is better still, giving about 2,700 cycles. The extra-light loaded type of cable circuit (H-44, which has been the standard loading system for long distance use for some time) will give a band even wider, extending up to at least 3,000 cycles.