Bell Labs

Bell Telephone Laboratories (or sometimes AT&T Bell Laboratories), best known as Bell Labs, was originally the research and development arm of the United States Bell System. It was the premier corporate facility of its type, developing a range of revolutionary technologies from telephone switches to specialized coverings for telephone cables, including the famous discovery of the transistor.

Calculators built by Bell Labs

• Model I - Complex Number Calculator, completed January 1940, for doing calculations of complex numbers
• Model II - Relay Calculator or Relay Interpolator, September 1943, for aiming anti-aircraft guns by interpolating from positions
• Model III - Ballistic Computer, June 1944, for calculations of ballistic trajectories
• Model IV - Bell Laboratories Relay Calculator, March 1945, a second Ballistic Computer
• Model V - Bell Laboratories General Purpose Relay Calculator, two were built: July 1946 and February 1947. These were general-purpose programmable computers using electromechanical relays.
• Model VI - November 1950, an enhanced Model V.