Sumlock ANITA Calculator - Further Information About The Early ANITA Calculators

Further Information About The Early ANITA Calculators

• The first of the ANITA models was called the Mk VII (i.e. Mark VII) because the development of the mechanism of the Sumlock mechanical calculators made by the company had already gone through design numbers Mk I to Mk VI. So the next number in the series was used for the first electronic design.
• The moulded plastic casing of the first ANITA calculators was particularly complicated for the time, and required development of new techniques by the moulding company. Originally moulded in ABS the material was later changed to polycarbonate for improved fire resistance.
• Operators converting from mechanical machines to the new electronic ANITA calculators often complained initially that the key stroke was too light and did not give the feel of the mechanical machine. Also, they missed the noise of the mechanism which indicated that the calculation was taking place and went quiet when the calculation was completed.
• An article of 1965 on cold cathode tubes from Mullard Ltd. (a British manufacturer of these devices, which also produced a prototype calculator using them) gives an insight into why they were used in these calculators at the time - "... They are an accountant's dream; a typical modern tube has a life expectancy several thousand times better than the conventional thermionic tube, although they employ voltages of the same order. They are much cheaper than either semiconductor devices or vacuum tubes; they do not require costly materials with a high degree of purity in their manufacture, nor do they need transformers or cooling systems to operate. The tubes require no warm-up period and they can take severe overload."