Early Anita Desktop Calculators

Anita Mk 12


Display: 12-digits using 'Nixie'-type tubes.

Function: 4-function, square root.

Technology: Dektatron counter tube, cold cathode tubes, vacuum tubes, discrete transistors and other components.

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 Dekatron and cold-cathode tubes.

The Lamson Industries (the parent company) annual report for 1967[1] mentions the Mk 12:
"Several of the research achievements of 1966 are illustrated in the report.  Foremost was the introduction of Anita Mark 12, a simplified keyboard electronic calculator designed in the first instance for the continental market, and now coming into production."
This suggests that the 10-key machine was favoured in continental Europe but the full-keyboard machines (the Mk 8 and Mk 9) were more popular in Britain.

Price in 1968: £480[2] (about US$1,150).

An advertisement from October 1966 says[3]:
"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."

Click here to see an advertising brochure for the ANITA Mk 12 (pdf format).


Photograph of the ANITA Mk 12 from an advertising leaflet.

ANITA Mk12 inside

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

Anita Mk12 inside

Looking down on the top shows the array of display boards, each carrying a 'Nixie'-type display tube.

ANITA Mk12 power supply

The power supply at the rear of the calculator has a circuit board which carries a pair of ECC81 (12AT7) double-triode vacuum tubes just above AC plug.

ANITA Mk12 display board

One of the display boards removed from the ANITA Mk 12. This caries the 'Nixie'-type display tube on the right, driven by the row of discrete transistors along the bottom.  Compare this with the display board from the Mk 8 calculator, below, which drives display tube with cold-cathode tubes.

Display board from Mk 8

Display board from an earlier ANITA Mk 8 where the display tube is driven by cold-cathode tubes, shown for comparison with the one from the ANITA Mk 12, above.

All of the photographs of the actual ANITA Mk 12 on this page are courtesy of Hans Bloemen. Hans has his own Calculator Museum site at http://www.calculatormuseum.nl/

Roland Huisman has posted a fascinating video on Youtube with a demonstration of the internal workings of his restored ANITA Mk 12 at https://www.youtube.com/watch?v=dKAyLnBjS3Q&feature=youtu.be.  This is recommended viewing to see how this machine which is intermediate between tube and transistor technology worked.


  1. The Times, April 6, 1967.
  2. "Focus on ANITA", advertisement, Office Methods and Machines, June 1968, p41.
  3. "NOW - ANITA MK 12", advertisement, Office Methods and Machines, October 1966.

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Text & photographs copyright © 2002 - 2023 Nigel Tout, except where noted otherwise.