Notched Disk Memory : Jacob Rabinow

Experimental Model of Notched Disk Magnetic Memory Device
ca. 1951

In the early 1950’s, the National Bureau of Standards undertook a program of electronic computer development for various government agencies. Rabinow was a consultant to the group doing this work. He became particularly interested in the magnetic tape units. One day at lunch, group leader Samuel Alexander asked Rabinow if he could design a machine that could record on and read from large (8 x 10) sheets of stackable magnetic material. Rabinow instead proposed recording on circular discs that could be stacked on a vertical spindle. If enough space was left between them, a reading head or recording head could run in it.

Not satisfied with the limitation on the number of discs this solution entailed, Rabinow went on to invent a machine that could store and read and even larger number of discs. Every disc on the machine’s spindle had a pie section removed from it so that a trough was formed through which the recording and reading heads moved. If the heads’ movement through the trough was stopped at a particular position, a single disc could be turned through the heads.