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Regarding the techniques for selecting desired frames, the Memex description
does depart from earlier microfilm selectors. Most of the schemes suggested involved
attaching a code, or set of codes, directly to a microfilm frame, and then employing a
sequential search through all the frames to find the matching codes. This was the method
used in the MIT Rapid Selector. But, as mentioned above, it was not the method
suggested by the Memex article. Instead, a system similar to telephone switching
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exchanges would be employed, with the switching done using vacuum tubes for high-
speed selection.
Actually, there are two aspects of this selection technique that are worth
reviewing. First is the telephone exchange model. Bush seems to have been aware of
ongoing developments at Bell Telephone Laboratories, so he may or may not have been
familiar with specific attempts to use telephone switch technology for other purposes.
For example, beginning in 1937 George Stibitz was using telephone relays to create first
a simple adder and later a complex number calculator, called the Relay Calculator. The
telephone switch idea, as a selection mechanism, implies that the microforms within a
Memex may need to be stored in a physical arrangement corresponding to each item’s ID
number (perhaps an accession number). For example, when the final number in the ID
has been processed by the last switch, the machine should be pointing at the physical
location of the microform frame, just as in a telephone switch it finally arrives at the
location of the dialed line.
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