The use of magnetic discs for the recording and reproduction of music was well known before 1948 when a representative of the U.S. Army Aberdeen Proving Grounds asked NIST engineers to suggest and develop a magnetic memory device of very large capacity and of very short access time.
The use of magnetic discs was obvious but the problem of large storage was difficult. The discs would have to be separated by appreciable distances so the writing and reading heads could move between them. It was important to mount the discs very close to each other and still have room to reach their surfaces without separating or moving them off their normal bearing supports. This was achieved by cutting a notch in each disc that extended from the periphery to a point about half the radial distance from the center. By using only the area of the disc on each side of the notch, three quarters of the area of each disc could now be accessed with the disc firmly mounted on its bearings and without the disc being separated by any appreciable spacing from discs on both sides.
Notched Disk Memory Device Schematic Diagram
Small Model of Notched Disk Memory Device
Jacob Rabinow - Inventor of the Notched Disk Memory Device
Last Updated on October 24, 2004
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