1950s-1960s MADAS Model 20BTG #94046
Technology: Stepped drum, fully automatic. Digits: 10 keyboard, 2×10 counter, 2×20 accumulator Dimensions: Body 240W x 305D x 230H, carriage width 380mm Weight: 17.6 kg Manufactured: Zurich, Switzerland, 1950s-60s Sold by Peackock Pty Ltd, Melbourne, Australia.
Purchased from John Wolff. As John notes, this B-series machine “has a “negative multiplication” control - the small “±” lever at the bottom left of the A-series keyboard has been promoted to an extension at the left of the multiplier bar. There were more significant changes internally, with the addition of a power-assisted mechanism to provide a lighter touch for the multiplier bar and the division setup key. The changes were mainly in the control mechanisms around the multiplier, and did not affect the calculating mechanism. The B series also provided a number of new interlocks between the function keys to prevent mis-operation. [ This machine] … has two additional keyboard controls which were available as optional extras. On the left-hand side there is a small lever which can be used to lock the Repeat key down, to save holding it when calculating squares. On the right is a similar lever marked with a square root symbol. This does not perform an automatic square root calculation, but simply modifies the operation of the Division key to assist in performing the manual square root algorithm.” [http://home.vicnet.net.au/~wolff/calculators/Tech/MadasATG/Intro.htm]
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