Differential analyser

The differential analyser is a mechanical analogue computer designed to solve differential equations by integration, using wheel-and-disc mechanisms to perform the integration.^[1] It was one of the first advanced computing devices to be used operationally.^[2] In addition to the integrator devices, the machine used an epicyclic differential mechanism to perform addition or subtraction - similar to that used on a front-wheel drive car, where the speed of the two output shafts (driving the wheels) may differ but the speeds add up to the speed of the input shaft. Multiplication/division by integer values was achieved by simple gear ratios; multiplication by fractional values was achieved by means of a multiplier table, where a human operator would have to keep a stylus tracking the slope of a bar. A variant of this human-operated table was used to implement other functions such as polynomials.