History of Relay Computers

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The first working programmable computer (!) was the Z3, designed by Konrad Zuse and completed in 1941. This computer was implemented with telephone relays. Here are some of its characteristics:

  • Data format: 22 bit binary floating point (1 bit sign, 7-bit exponent, 14-bit mantissa).
  • Provided operations: add, subtract, multiply, divide, square root
  • Data memory: 64 words of 22 bits implemented with relays
  • Program memory: punched film
  • Frequency 5.3 Hz
  • Relays: 2600 (1400 of them for the data memory)
  • Power consumption: 4000 Watts
  • Calculating speed: add .8 seconds, multiply 3 seconds

A good description is here: http://ed-thelen.org/comp-hist/Reckoners-ch-2.html

Although the Z3 was the first, it was not an influential computer since its details were not published beyond a rejected patent application.

Recent History

A number of people have made one-off relay computers in recent years, including:

Harry Porter's Relay computer: http://web.cecs.pdx.edu/~harry/Relay/

  • 415 relays

Jon Stanley's Relay computer "RC-2": http://www.electronixandmore.com/projects/relaycomputertwo/index.html

  • 281 relays

Phil Ryal's "RC-3": http://www.computerculture.org/projects/rc3

  • 418 relays

Fredrik Andersson's "Zusie": http://www.nablaman.com/relay/

  • 268 relays

Rory Mangles' TIM-8 computer: http://www.northdownfarm.co.uk/rory/tim/

  • 152 relays

Kilian Leonhardt's relay computer

  • 1500 relays