Two-piece fence from a circa 1950s drum memory system, more than likely a prototype since there are no part numbers or other identifying features. This device may have marked a major milestone in the development of disk technology. It would allow the read/write heads to be movable for the first time instead of fixed paving the way to disk drive technology. This system made it possible for a single head to replace many fixed heads on a single surface since this gave the magnetic memory peripheral the ability to seek to different tracks! This arrangement also allowed for disks to be stacked on top of one another, greatly increasing storage capacity.
The smaller of the two pieces, measuring 1 7/16″ x 1″ x less than 1/8″ thick, appears to have a continuous loop of gold attached to a glass substrate. The longer piece, measuring 5 15/16″ x 13/16″ x 1/8″ thick, has two gold loops attached to an insulator which in turn is attached to a metal strip. The smaller piece has two leads mounted to it while the larger has four. The larger unit may of had a charge applied to one of the loops and used the other to pick up signals since it has four leads. Conversely, the smaller piece, acting as a coil, may have induced an electromagnetic field which was picked up by the larger piece when it passed by, creating some kind of analog signal which could then be processed into drum track position. In any case, precise workmanship was put into creating this fence system. Under magnification, they look like pieces of art! The smaller piece is displayed in a Riker box, with a magnified close-up image of its surface above. Also includes a color glossy 8.5 x 11 enlargement of the same image, revealing the intricate detail of the gold loop. In overall fine condition.
Terms and abbreviations used in our descriptions.