Some aspects of magnetic sound recording

The development of magnetic sound recording from the end of the last century to the present day is described, more particularly from the aspects and results of the introduction of the oxide-coated tape by Pfleumer and the magnetizing or biasing of this tape with a supersonic frequency by Braunmÿhl and Weber. The extension of these developments which has taken place since the war, especially in Great Britain and the U.S.A., is referred to and the improved effect of biasing with a supersonic frequency is dwelt upon. The explanations advanced by research workers such as Wetzel and Montani for the improvement obtained by high frequency biasing are considered and discussed at considerable length, and a more detailed explanation is advanced. Finally, the paper deals with some aspects of signal erasure utilizing a.c. mains and high frequency currents.