page_title: Comptometer
section_title: Model F
hierarchical_section_title: Comptometer / Development / Model F
caption_attribution_description: Deutsch: Comptomer, eine Rechenmaschine für Addition
context_page_description: The comptometer was the first commercially successful key-driven mechanical calculator, patented in the United States by Dorr E. Felt in 1887.
  A key-driven calculator is extremely fast because each key adds or subtracts its value to the accumulator as soon as it is pressed and a skilled operator can enter all of the digits of a number simultaneously, using as many fingers as required, making them sometimes faster to use than electronic calculators. Consequently, in specialized applications, comptometers remained in use in limited numbers into the early 1990s, but with the exception of museum pieces, they have all now been superseded by electronic calculators and computers.
  Manufactured without interruption from 1887 to the mid-1970s, it was constantly improved. The mechanical versions were made faster and more reliable, then a line of electro-mechanical models was added in the 1930s. It was the first mechanical calculator to receive an all-electronic calculator engine in 1961, with the ANITA Mark VII model released by Sumlock Comptometer. This created the link between the mechanical calculator industries and the electronic.
context_section_description: The production of this model started in 1915 and lasted five years. The error detection mechanism is moved inside the box and the release key is red. This machine is the last machine without the Comptometer logo inscribed on its front and back panels.
caption: Model J (1930s)
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