New Manufacturing Techniques For Precision Transformers for the L3Coaxial Carrier System

Early in 1951 the Western Electric Company set up manufacturing facilities for the production of the L3 coaxial system.* This new system transmits the frequency hand from 0.3 to 8.353 mc over coaxial cables. To counteract the attenuation of these cables, line amplifiers are provided every four miles. The 2504A transformer is used both at the input and output of these amplifiers to couple them to the cable. The system is designed so that the parasitic elements of the transformer are used to help shape the transmission characteristic. Since upwards of 2,000 of these transformers are used in a long cable system, it is necessary that the constants of each transformer be held to an extraordinary degree of precision, and that the temperature variation and aging effects be virtually eliminated. * L. H. Morris, CJ. H. Lovell, and F. R. Dickinson, The L3 Coaxial System, R.S.T.J., 32, July, 1953. A technical description of the 2504A transformer appears on page 891. 291 292 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1 9 5 5