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(via Retro Thing: The Smallest Analog Computer Ever Made?!)
From the early 1960s brochure: “Donner’s Model 3500 is a full-fledged analog computer weighing just 28 lbs. Designed for engineers, educators and scientists, it can be used to study almost any physical system that can be described by differential equations. It can be operated on desk tops and benches by anyone who can run a slide rule. The standard 3500 contains 10 amplifiers, stabilized or unstabilized as the user chooses. The computer performs accurately with 1% or 0.1% computing components, and is furnished ready-to-work for $1850, depending upon specific equipment desired.”
