John Wolff's Web Museum

The Madas Automatic Desk Calculator

Madas20ATG.jpg (8kb) MADAS Model 20ATG, S/N 70052
Functions: ASMD, automatic multiplication and division, back transfer
Technology: Electro-mechanical, Leibniz wheel
Digits: 10 keyboard, 10 multiplier, 2x10 counter, 2x20 accumulator
Dimensions: 9-1/2"W x 12"D x 9"H, carriage width 15", weight 38 pounds
Manufactured: Switzerland, 1930s to 1950s.
Original Owner: The University of Sydney (ex A.G.Bromley collection)


These pages contain a series of notes and photographs which illustrate the basic principles and the internal mechanism of the Madas fully-automatic desk calculators. They are presented here to further the understanding and preservation of these historic instruments.

The notes were based originally on over 40 pages of hand-drawn notes and sketches, and about 100 photographs, that I took to assist in the overhaul of Madas No. 70052 during 2002.

I am indebted to the late Mr Ray Mackay of Melbourne, a former Madas technician, for his assistance and encouragement with this project. Ray's "Recollections on the Madas Calculator" are available on the Web and should be read in conjunction with these notes.

If you are planning to repair or overhaul a Madas, please review the Notes on overhauling a mechanical calculator (in the Technical section of this site) before starting work.

While I believe the descriptions following to be substantially correct, I do not guarantee that they are entirely accurate, complete, or applicable to any other machine. No responsibility will be taken for any consequences arising from the use of these notes by others. Do not dismantle your Madas in the expectation that these notes alone will tell you how to get it back together!

I would welcome you feedback, advice of errors, or suggestions for improvement via the enquiry form.


  1. Fundamentals - add and carry
  2. The keyboard
  3. The carriage registers
  4. Carriage shift and clear
  5. Automatic division
  6. The multiplier unit
  7. Putting it back together
  8. Removing and refitting the Triplex carriage
  9. Description of operation

Original text and images Copyright © John Wolff 2002-13.
Page created: 12 December 2002. Last Updated: 9 February 2013

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