The L3 Coaxial System - Foreword

Copyright, 1953, American Telephone and Telegraph Company The L3 Coaxial System Foreword The articles in this issue are devoted to different phases of the development of a new system for the transmission and utilization of broader frequency bands on existing or new coaxial cables. This new system, which is called the L3 carrier system, represents the latest phase of development activities begun in the late twenties. It permits far more intensive exploitation of the cable medium than its predecessor, affording the option of providing, in each direction on a pair of coaxial tubes, either I860 telephone channels or 600 telephone channels and a 4.2 megacycle broadcast television channel. These results have been attained through wide extension of previous art. New electron tubes, transformers, inductors, and other circuit elements have been designed for extreme precision in respect to stability and other performance factors. Statistical quality control techniques are being applied to obtain the benefits of closely controlled distribution of the performance of circuit elements and system units. Fundamental to the program has been the devising of techniques for achieving hitherto unobtainable accuracies in the measurement of impedance, loss, phase and other transmission properties. To provide precise attenuation and delay characteristics over the wide frequency band, new techniques of network synthesis have been developed. Refined system analysis and circuit design have derived maximum performance from component capabilities.