John Wolff's Web Museum

Full-function Ten-key Calculators

Facit 10-07



Full-function ten-key calculators sought to combine the convenience of the ten-key input mechanism (from the well-established adding and listing machines) with the computational abilities of the fully-automatic rotary calculators. These machines first appeared in the late 1940s, and reached their peak of development in the mid-1960s, just in time to be superseded by the new electronic calculators. The machines seem to have survived longer in Europe, with manufacturers such as Olympia and Walther still filing patent applications into the early 1970s.

The full-function ten-key machines can be divided broadly into printing and non-printing designs, with reciprocating or rotary mechanisms. Some manufacturers (eg Olivetti, Precisa, Facit) were able to develop fully-automatic machines based on their existing mechanisms, while others (eg Diehl, Monroe) set out to develop (or purchase) completely new designs. Some of the new machines used multiple technologies, combining the established pin-box and reciprocating racks for addition and subtraction with a separate rotary actuator for rapid multiplication and division.

Some of the late-model machines were starting to be designed on a computer-like "functional block" model, with a mechanical "data bus" of toothed racks to transfer values between the various blocks, and a state-based micro-programming mechanism to control the sequence of internal operations. The racks and programming mechanisms of machines such as the Diehl Transmatic bear more than a passing resemblance to the "store" and "barrel" of Babbage's analytical engine of the 1830s.

The illustrations below show some typical examples of printing and non-printing machines using a variety of technologies. Click on the photos below for larger illustrations, or follow the brand-name links to see other machines from the same manufacturers.


Full-function ten-key calculators - printing.


Divisumma 24 (8kb) Olivetti Divisumma 24, S/N 1D-786832
Technology: pinbox with reciprocating racks
Dimensions: 250W x 430D x 240H
Weight: 14.38kg
Manufactured: Italy, 1956-1960s

The Olivetti Divisumma 24 (D24) is a large full-function printing calculator with fully automatic multiplication and division.

The calculating mechanism was designed by engineer Natale Capellaro, and the exterior by the noted architect and industrial designer Marcello Nizzoli. The machine first appeared in 1948 as the manually-operated Divisumma 14. It was extensively redesigned in 1956 to become the Divisumma 24, which continued in production in various forms well into the 1960s. An electronic Divisumma 18 appeared in 1973.

The D24 operates as an adding machine in the normal manner, with keys for add, subtract, total, and subtotal. To divide, the dividend is entered into the accumulator with the add key, and the divisor is set on the keyboard. When the division key is pressed the machine completes the calculation automatically and prints the quotient and the remainder.

Problems in multiplication are entered as written, eg "123 x 456 = ". The machine stores the first value, performs the calculation, and prints only the result. There are options for controlling the printing of totals and accumulated subtotals during repeated multiplications.

The Divisumma performs short-cut multiplication for numbers over 5. It takes 6 machine cycles to multiply 5 x 5, but only 3 cycles for 2 x 2 or 9 x 9.

The internal storage register which holds the first factor in a multiplication is directly accessible from the keyboard (via the M and IM keys), and can be used as a general-purpose memory register. Values can be entered directly or back-transferred from the accumulator, and can be returned to the accumulator or used in a subsequent multiplication.

Monroe 011K114 (8kb) Monroe "Mach 1", Model 011K114, S/N B410081
Technology: pinbox, reciprocating racks, pinwheel actuator
Digits: 10 input, 7 multiplier, 15 output
Dimensions: 250W x 395D x 170H
Weight: 10.9kg
Manufactured: Monroe, Holland, 1960s

This Monroe ten-key calculator is based on the Ultra 804, developed by Oerlikon-Bührle in Zurich in the late 1950s. Oerlikon was originally a machine-tool manufacturer which branched out into armaments and munitions, and took up calculators as a civilian enterprise after the 1939-45 war. The firm later returned to military work, and sold its final calculator design to Monroe.

The mechanism was designed by Gustav Schenk of Oerlikon, and is described in his US Patent 3082942 (filed in 1961). The patent is assigned to the Litton World Trade Corporation of Panama City. Schenk continued to develop the machine for Monroe during the 1960s.

The machine combines the total and sub-total functions of the printing calculators with the fully-automatic multiplication, division and back-transfer of the top-end rotary machines. The keyboard controls are clear and simple, and the machine operates quickly and quietly. The mechanism uses a combination of pin-carriage and racks for the entry and printing functions, with a rotary actuator and carry mechanism based on a miniature version of the Odhner-style pinwheel. The machine was manufactured in Monroe's European factory in Amsterdam.
Keyboard detail (29kb)

Diehl Transmatic S Diehl Transmatic S, S/N 22126632
Technology: pinbox, reciprocating racks, pinwheel actuator
Digits: 12 input, 8 multiplier, 16 output
Dimensions: 295W x 405D x 200H
Weight: 18.4kg
Manufactured: Diehl Rechenmaschinenfabrik, Nürnberg, Germany, 1965-67

Heinrich Diehl's foundry and press works was established in Nürnberg in 1902, but was not involved with calculating machines until the 1950s. In 1952 the firm produced a range of stepped-drum rotary calculators based on the long-established "Archimedes" line, followed by fully-automatic ten-key printing machines from 1963 until 1972.

The Transmatic S was the top-line machine in the Diehl range. Addition and subtraction operate in adding-machine fashion, with separate total and sub-total keys. Problems in multiplication and division are both entered in a consistent algebraic fashion: 2 x 3 =, or 2 : 3 =. There are two independent 16-digit accumulators selected by the I and II keys, a separate 16-digit constant register, an 8-digit multiplier register. and a back-transfer mechanism.

The Transmatic mechanism is based on reciprocating racks and rotary gear registers, with a rotary pinwheel actuator for high-speed multiplication and division. The machine contains a total of seven registers, interconnected by a mechanical data bus of 16 toothed racks. Sequencing of internal operations is controlled by a step-wise programming mechanism and an arrangement of cams. The printing mechanism has 16 numeric places, with a further three columns of symbols on the right-hand side. The paper roll is 100mm wide.

The mechanism is built on a pressed-metal frame, hinged to a substantial cast-aluminium baseplate, and surrounded by a heavy die-cast alloy casing.
Internal view (29kb)
Internal view with mechanism raised (29kb)
Keyboard detail (28kb)

Diehl Decima Diehl Decima, S/N 24152176
Technology: pinbox, reciprocating racks, pinwheel actuator
Digits: 10 input, 8 multiplier, 12 output
Dimensions: 310W x 410D x 200H
Weight: 13.6kg
Manufactured: Diehl Rechenmaschinenfabrik, Nürnberg, Germany, 1967-70

The Diehl Decima was introduced in 1967 as a lower-cost alternative to the Transmatic (above). The machine retains the fully-automatic multiplication and division, but with reduced numeric capacity. It eliminates the dual accumulators, constant register, and back transfer functions. The internal mechanism is similar but not identical to the Transmatic, and has a plastic rather than alloy casing.

Hermes-Precisa Model 167-12 Hermes-Precisa Model 167-12, S/N A865056
Electric, 12/13 columns, decimal
Dimensions: 260W x 310D x 175H
Weight: 9.3kg
Manufactured: Precisa AG, Zurich, 1968

The Precisa Model 167-12 is a relatively compact ten-key machine with fully automatic multiplication and division, memory, automatic back transfer, and constant storage. This machine is housed in a 3-part plastic casing finished in the Hermes green.

The Precisa 167 has a particularly clear and simple keyboard layout, with only 14 function keys and 2 control levers. One of the control levers locks the memory key to prevent automatic clearing of the contents, and the other selects negative multiplication. Both levers are located next to the keys that they modify, and operate in a consistent direction.
Keyboard detail (31kb)

Totalia S4-GT Lagomarsino "Totalia" Model S4-GT, S/N 2008415
14/15 columns, fully automatic, with grand total
Dimensions: 280W x 445D x 200H
Weight: 14.1 kg
Manufactured: Milan, Italy, 1970

The Totalia S4-GT is a late-model fully-automatic machine from around 1970. (The instruction card is dated November 1969). It is an attractive and well-built machine, with a pressed-metal frame and an all-plastic casing. There are 15 places in the printing mechanism, 14 in the keyboard, and 13 in the multiplier. The machine has a grand-total register, a constant-factor register, and a key for percentage calculations.
Keyboard detail (29kb)

Walther Diwa 32 Walther Diwa 32, S/N 2001934-3068042
Technology: pinbox, reciprocating racks
Digits: 11 input, 12 output
Dimensions: 260W x 425D x 160H
Weight: 11.2kg
Manufactured: Walther Buromaschinen GmbH, Gerstetten, Germany, 1970-72

The Walther Diwa 32 extends the successful three-function Multa 32 from 1959 to provide fully-automatic multiplication, division, and chain calculations.

Addition and subtraction operate in adding-machine fashion, with total and sub-total keys. Multiplication and division operate algebraically, but with separate "Equals" keys. Every item or result is immediately available for re-use in a subsequent calculation without needing a separate back-transfer operation. The keyboard is relatively simple, with only ten function keys and two sliding levers (for constant storage and accumulation of products).

The mechanism is based on Walther's established technology of pinbox and reciprocating racks, with rotary-gear registers for total, constant, and multiplier storage.

The Diwa 32 was one of the very last of the full-function mechanical calculators to be brought to the market. When it was introduced in mid-1970 Walther was already selling an electronic four-function printing calculator, but at several times the price. Walther literature from the period suggests that they expected both product lines to continue in parallel, with the speed and convenience of the electronic machines coming at a significant cost premium. However, by the end of 1972 the introduction of large-scale integration (LSI) had driven the prices to parity, and the sales of mechanical calculators came to an abrupt end. The Diwa 32 was discontinued after only two years.
Keyboard detail (29kb)


Full-function ten-key calculators - non-printing.


Facit 10-07 Facit Model 10-07, S/N 1571422
Technology: rotary pinwheels, pin-box register for multiplier
Digits: 11 keyboard, 9 counter, 16 accumulator
Dimensions: 275W x 350D x 190H
Weight: 15.0 kg
Manufactured: Sweden, 1967-1972

Facit of Sweden built ten-key pin-wheel calculators from the 1930s using a two-row keyboard layout adapted from the "Dalton" adding machine of 1902. Their first fully-automatic machine (the ESA-0 of 1949) and the later CA1-13 (1956-73) both used the Dalton keyboard. The first Facit machine to use the ten-key numeric keypad was the manually-operated CM2-16 of 1959, with the fully-automatic CA2-16 following in 1962. This Model 10-07 from the late 1960s is the culmination of more than thirty years of pinwheel calculator development.

The mechanism still uses the "inverted" pinwheel design, with the accumulator and counter registers fixed in position at the top of the machine. The keypad enters values directly into the 11-digit pinwheel rotor, and into an 8-place pinbox register which is used for multiplier or constant storage. The machine performs "short-cut" multiplication, and operates at 400 cycles per minute.

The rotor travels the full width of the machine, so that it can engage with either the accumulator or the counter register. The rotor can receive back-transferred values from either register, allowing on-going calculations involving the results of a division, and it can transfer values between the registers, allowing the counter to be used as a memory or for the accumulation of products. The machine has a total of 24 function keys (in addition to the numeric keypad), but the keyboard arrangement is clear and easy to use.
Keyboard detail (29kb)

Hamann 505 SCM Hamann 505 "Tenkeymaster", S/N 517888
Technology: ratchet wheel
Digits: 9 keyboard, 8 counter, 16 accumulator
Dimensions: 370W x 410D x 220H
Weight: 17.8kg
Manufactured: Hamann-Rechenmaschinen GmbH, Berlin, 1965

Engineer Christel Hamann (1870-1948) had produced several original calculating mechanisms (including the Gauss and Mercedes-Euklid) before taking charge of calculator design at the German Telephone and Cable Works (DTW) in 1922. The Hamann Manus of 1925 was outwardly similar to the Odhner pinwheel machines, but used an entirely new actuator mechanism based on a uni-directional ratchet wheel. Subtraction was accomplished by a reversing mechanism in the carriage which was driven through a second set of star wheels. The carriage was displaced a short distance sideways to select the appropriate set. The Hamann Manus continued in production in various forms into the 1950s.

The Hamann Delta and Selecta machines of 1934 used the same basic actuator and carriage with a full-keyboard setting mechanism, and a pair of Plus and Minus keys to control the carriage-based reversing mechanism. The full keyboard was later replaced with a ten-key setting mechanism, first introduced on the Hamann 300 in the early 1950s. This machine progressed through several versions to the final fully-automatic Hamann 505 from 1962. The machine illustrated was built in 1965.

In 1958 DTW's calculator business was restructured as Hamann-Rechenmaschinen GmbH, and was sold to SCM in America.

The internal view of the Hamann 505 shows the moving carriage with the counter and accumulator registers mounted above the keyboard, with the bank of 16 ratchet wheels behind and a setting register at the top. Only 9 of the actuator wheels are settable from the keyboard - the leftmost 7 are only for carry propagation. The carriage moves only a relatively short distance, and is fully enclosed within the external casing.
Keyboard detail (27kb)

Olympia RA-20 Olympia Model RA-20, S/N 03366
Technology: reciprocating racks, travelling carriage
Digits: 10 keyboard, 11 counter, 20 accumulator
Dimensions: 400W x 340D x 195H
Weight: 17.9 kg
Manufactured: Germany, 1965

The Olympia RA-20 is a full-function ten-key calculator with an external travelling carriage. The mechanism is a development of a calculator design that first appeared in the late 1950s (US patents 3116873 and 4, filed by Ernst Trümpelmann et al in 1958). The mechanism is based on a pinbox and reciprocating racks, with rotary-gear registers for multiplier and constant storage. The accumulator and counter registers are mounted in the travelling carriage, with a rotary carry mechanism in the body of the machine. Subtraction is accomplished with a second set of reversing star wheels in the carriage, in the same manner as in the Hamann machines (above).
Keyboard detail (29kb)

Contex 55 Contex Model 55, S/N 493011463
Technology: reciprocating racks (rotary movement)
Digits: 10 keyboard, 11 accumulator, 10 quotient
Dimensions: 205W x 290D x 120H
Weight: 4.30kg
Manufactured: Carlsen Bros, Denmark, 1968-1970s.

The Contex 55 from 1968 is a relatively simple ten-key machine which provides fully-automatic division and "on-the-fly" multiplication. There is no provision for back-transfer, constant storage, or any of the more advanced features of the machines above. The mechanism is a development of the successful Contex 10, 20, and 30 machines that were first introduced in 1957. Please refer to the Contex page for further details.

Resources for further information:

Original text and images Copyright © John Wolff 2007-14.
Last Updated: 13 January 2014

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