Transaction section: Preprint of corresponding pages from the current annual AIEE transactions volume

THE development of thin permalloy tape and its use in cores have resulted from the increasing need for efficient magnetic structures at high frequencies. For some time for example, the trend in the telephone plant has been to the use of higher frequencies in the longer distance toll circuits. The reason is that these permit the simultaneous transmission of a larger number of telephone conversations over a single conducting circuit. The coaxial transmission system developed before the outbreak of the war, operates over the range of about 64 to 3,200 kilocycles and required transformers for repeater amplifiers and terminals capable of passing this wide band efficiently. Eddy current effects at these frequencies preclude the use in such transformers of magnetic material in conventional thicknesses.