The Relay Circuit Analyzer Case 22108; MM-53-1400-09 and 53-1800-17 [Bell Laboratories Technical Memorandum]

Murray Hill, N. J.: Bell Telephone Laboratories, Incorporated, 1953. Wraps. Very Good. [1-cover sheet], [1-abstract], [1]-14 leaves + 4 plates (2 folding). Stapled upper left. 10 7/8 x 8 3/8 inches. Reproduced typescript. Plate slightly larger at 11 x 8 1/2 inches. The main text leaves and abstracts have fours holes punched at the spine. The plates in the rear are not hole punched. There is some mild paper toning and fold creasing to the rear pages near the staple. Wraps. The Proceedings of the I. R. E., Vol 41, pp. 1348-1351, October 1953 first published a description of the Relay Circuit Analyzer under the title "Machine Aid for Switching Circuit Design." The Bell Laboratories Monograph series (#2159: March 1954) also published that description.

We were delighted to discover this internal Bell Laboratories Memorandum, "The Relay Circuit Analyzer - Case 22108," among Shannon's files. It not only precedes the first public description in the Proceedings of the IRE by several months, but it includes much additional material, including (importantly) circuit designs not found in the IRE or the Bell Monograph descriptions. It appears Bell Labs wanted the design all to themselves. And the distribution list of eighty-nine Bell System scientists proves how widely it was valued.

The public description contains a reproduced photograph of a nicely machined, professional-looking front panel. In contrast, we love that this Memorandum shows the front panel of the Relay Circuit Analyzer constructed from unadorned plywood with stickers for labels on the buttons and switches. Exactly what you'd expect for a laboratory-grown and tested machine.

Shannon's brilliant 1938 master's thesis proves that logical designs can be unambiguously constructed in electrical circuits. Design engineers then and now are tasked with how efficiently they can build a machine - fewer components keep costs down and complexity to a minimum. The Relay Circuit Analyzer took this theory one step further, using a purpose-built machine to remove unnecessary elements while testing a circuit against its design requirements.

"This memorandum describes a machine (made of relays, selector switches, gas diodes, and germanium diodes) for analyzing several properties of any combinational relay circuit which uses four relays or fewer. This machine, called the relay circuit analyzer, ... can (1) verify whether the circuit satisfies the specifications, (2) make certain kinds of attempts to reduce the number of contacts used, and also (3) perform rigorous mathematical proofs which give lower bounds for the numbers and types of contacts required to satisfy given specifications." (abstract)

"This paper [ Machine Aid for switching circuit design ] describes the first 'verification' machine, built at Bell Labs and called the 'relay circuit analyzer.' The machine 'verifies whether a circuit satisfies given logical specifications and also makes a systematic attempt to reduce the circuit to simplest form." (Origins of Cyberspace)

PROVENANCE: The personal files of Claude E. Shannon (unmarked). The only complete example in Shannon's files.

REFERENCES:
Sloane and Wyner, "Claude Elwood Shannon Collected Papers," #74 and #80
Hook and Norman, "Origins of Cyberspace," #886 (referring to the 1953 IRE paper "Machine aid for switching circuit design").