Early Anita Desktop Calculators

Anita Mk 12


12-digit display.

The ANITA Mk 12 was the first ANITA with the now standard 10-key keyboard. It was introduced in 1966, before the Mk 11, and used transistors as well as a few vacuum tubes.

An advertisement from October 1966 says[1]:

A 10-key, three register, two store. Electronic Desk Calculator. Unique active registers allow an economy in design, giving performance equivalent to comparable four or five register equipment.
Any calculation can be re-traced to check and recall both products and quotients.
ANITA'S unique method of calculation and ring decimal point gives a continuously usable capacity of 10x10x11 and prevents any possibility of "overflow" on multiplication, no matter the size or number of the factors. Positive balance feature permits a change of sign of any intermediate or final result. Transfer of information between registers is obtained by use of the interchange control effecting maximum flexibility of operation at all times.
Additions to, or subtractions from, stored information are standardised automatically to any pre-set decimal point position so that there is no need for entry of any non-significant zeros.
Fully symbolised and colour coded keyboard is completely international in design and easily understood.
All cross register arithmetical operations are immediately available.
Direct access to internal stores at all limes.
Automatic clearance on reading totals from internal store prevents operating errors. Special interlocked control sequence permits these totals to be retained when required.
Special facilities available include:
1  Constants—Multiplier—Divisor—Dividend.
2  Fully automatic floating decimal point system.
3  Unique interchange control.
4  Accumulated results can be used as multipliers or divisors without pre-setting or cross register operations.

All of the photographs of the ANITA Mk12 on this page are courtesy of Hans Bloemen. Hans has his own Calculator Museum site at http://www.calculatormuseum.nl/


The arrangement of the electronics inside shows similarities to the earlier models, with each display tube being mounted on its own plug-in board.

Rear board

The circuit board at the rear of the calculator carries two vacuum tubes.

Display board

One of the display boards removed from the calculator. This uses transistors and carries the display tube on the right. Compare this with the display board from the Mk 8 calculator, below, which uses cold-cathode tubes.

Display board from Mk 8

Display board from an earlier ANITA Mk 8, shown for comparison with the one from the ANITA Mk 12, above.


  1. "NOW - ANITA MK 12", advertisement, Office Methods and Machines, October 1966.

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Text & photographs copyright © 2002 - 2017 Nigel Tout, except where noted otherwise.