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Chapter 6
Relay Calculators
Introduction
harles Babbage had planned to power his Analytical Engine
Cwith a steam engine-steam being the only feasible prime
mover available in the 1830s. In that same decade, however, others
were making discoveries that led to the electric motor: a source of
motive power more compact, cleaner, quieter, and most of all, much
more flexible than steam. By the early twentieth century, calculators
werejust one of many machines that were powered by electricity.
But electricity could do more than replace the steam engine or
human armas a source of power; it could also represent the numbers
themselves that a calculator handles. Electric circuits could replace
the cams, pins, gears, and levers that actually do the computation.
Hollerith’s electric tabulators took advantage of this property, and we
have already seenhow the rival Powers system, developed after 1911
to compete with Hollerith, suffered in comparison because it used
electricity only for motive power.
By the 1930s,a number of inventors recognized that the ability
(as well as the power) offered by electric circuits allowed one to build
a machine that could not only do arithmetic, but also direct a complex
ce- of calculations autom&@ly. T h i m e , had be&
Babbage’s d r e z and b