A review of the Bell Laboratories' digital computer developments

The Bell Telephone Laboratories have designed and built seven digital computers since the late 1930s. The seven types made were all electro-mechanical types using telephone systems relays and teletype transmitting and recording devices as their principal apparatus elements. Starting with the "complex number computer" as the pioneer and with the Model VI as its latest achievement, the Bell Laboratories computer development has spanned the pre-electronic computer development era. The seven types, known by Model numbers (with Model I being the designation of the complex number computer) are described. Two Model V computers were built. A table is provided that shows some statistical information about their size and use. The Models V and VI, although operating at electromechanical speed, offer several challenges to current electronic computers. While the same cannot be said of the Models I through IV, nevertheless, they have features of interest, which are described herein.