Thorsen tubes

Thorsen tubes are the memory components that make Dan Davis’s automata capable of learning and repeating operations without a human supervisor. Their importance lies not in granting machines human understanding but in turning demonstrated work into durable, reusable instruction: the same mechanism supports household routines, Flexible Frank’s adaptable tasks, and the more ambitious Protean Pete.

Definition and Operation

A Thorsen tube can be connected to a control circuit while a person manually guides a machine through an operation. The tube then retains what was done and can direct the machine through that operation again, or repeatedly, without renewed human supervision. Davis presents this as sufficient for an automated machine tool; more complex applications, including guided missiles and Flexible Frank, add side circuits.

Those supplementary circuits supply what Davis calls “judgment,” but he explicitly disputes the term. They are hunting circuits, programmed to look for specified conditions within limits and to trigger an instruction when those conditions appear. They can also interrupt the tube’s basic instructions when a cycle differs from the one originally recorded. The system therefore combines a stored procedure with conditional responses, rather than giving a machine human judgment.

Household Automation

The tubes made household work teachable as repeatable action. Davis’s example is dishwashing: Flexible Frank could be guided through clearing a table, scraping dishes, and loading them into a dishwasher once, after which he could handle later loads. Davis also describes a more ambitious possibility: a duplicate Thorsen tube could let the machine manage dirty dishes the first time it encountered them, without breaking one. That claim distinguishes a routine already learned from a routine preloaded into the machine.

The same underlying principle informed Hired Girl, Mark One. Davis describes its memory circuit as adapted from a guided missile and its cleaning devices and linkages as assembled from existing equipment, including a floor polisher, a soft-drink dispenser, and handling mechanisms used in atomic facilities. The machine searched for dirt and selected among sweeping, mopping, vacuum-cleaning, and polishing by consulting its stored instructions. The commercial advance, as Davis frames it, was not an entirely new component but the integration of existing mechanisms into an unsupervised cleaner.

Design, Production, and Limits

Davis’s account places the tubes within an engineering system shaped by available technology and practical constraints. Hired Girl’s production design relied largely on standard catalogue parts, with only two three-dimensional cams and a printed circuit requiring special treatment. He stresses that production engineering and the workable arrangement of existing components mattered as much as invention itself: the memory system’s usefulness depended on a machine that could also be built economically.

That dependence on the state of the art appears again when Davis considers voice control for the first Flexible Frank. He had not voice-coded the machine because the necessary analyzer and telephone exchange would have outweighed, bulked up, and cost more than the rest of the unit. Its controls instead required buttons on a control board. Davis treats this limitation as a problem of miniaturization and simplification, not as a failure of the memory principle: engineering could exploit an idea only when the supporting technologies were available.

From Flexible Frank to Protean Pete

When Davis returned to designing machines in 1970, he built Drafting Dan before rebuilding Flexible Frank. The new machine, renamed Protean Pete, was conceived as an all-purpose automaton able to perform almost anything a person could do if its Thorsen tubes were properly instructed. Davis expected that this general-purpose design would not persist unchanged: he anticipated descendants that would evolve into specialized devices, while seeking broad patent claims for the underlying concept.

Protean Pete contained three times as many Thorsen tubes as Flexible Frank. Davis had initially concentrated on teaching him commercial tasks for other people and had overlooked the possibility of using him for his own household work. Once that possibility became apparent, he began teaching Pete the domestic tasks Flexible Frank had learned. The episode shows that the tubes’ capacity did not by itself determine what a machine would do: their uses depended on which operations Davis chose to demonstrate and encode.

Significance

Thorsen tubes provide the technical link between Davis’s modest household cleaner and his increasingly versatile automata. They make labor transferable into a machine, but the transfer remains bounded by recorded operations, programmed searches, available components, and the engineer’s choices. The book’s recurring distinction between routine and judgment is thus built into the machinery itself: a tube can preserve and repeat a procedure, while the circuitry around it manages deviations without, in Davis’s view, creating a genuinely judging mind.