New steel tone tape machine

A slightly abbreviated translation of a paper published by the Lorenz Co. of Berlin giving a description of a new steel tape recording machine, which has been tested by the German broadcasting authorities and proved satisfactory [see Lorenz Berichte No. 1, Jan., 1936]. The tape used is 3 mm. wide by 0.08 mm. in thickness and the normal velocity of the tape is 1.5 m./sec. The machine posesses two large interchangeable drums to carry the tape. The tape leaves one drum, passes through an erasing and recording "head," over two guide pulleys, around the main driving drum and over two more guide pulleys and then through the reproduction "heads" and on to the other large drum. The "heads" are put into circuit as required. Each "head" consists of a pair of iron-cored coils, one on each side of the tape and kept against it by springs. The iron cores have flat chisel-shaped ends and are mounted with their axes parallel but out of alignment so that a short length of the tape is between them. Magnetisation is effected by passing d.c. through the coils and superposing the speech a.c. upon it, the a.c. is kept small so that the magnets all face the same way. A special frictional coupling is used to drive the drums at constant speed. The paper includes a theoretical treatment of the associated magnetic problems, and details are also given of the gear used to overcome the danger due to the large mechanical inertia of the loaded drums, which, if, for instance, the current should fail, might run on and tangle the tape.