General Electric differential analyzer
Some of the most widely used analog computers where known as differential analyzers. This picture of a General Electric differential analyzer comes from the UCLA engineering school which defined the machine as an “interconnected system of shafts, motors and gears, and electromechanical elements. The machine employs these mechanical elements, whirring, buzzing, and clicking away, to perform addition, subtraction, multiplication, and division, and the electromechanical elements for more complex functions.
“One of the most important elements of the differential analyzer is a Polaroid photoelectric system of unique design which GE developed. Fourteen of the highly sensitive devices are installed on the machine, thus permitting the accurate, speedy solutions of differential equations requiring as many as fourteen simultaneous integrations.”