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Calculators by Hans W. Egli, Zurich



MADAS Model 20ATG, 1950s


Egli nameplate (8kb)

Engineer Hans W Egli of Zurich first became involved with calculating machines in 1891, when he began to develop Otto Steiger's patent for a multiplying machine into a form suitable for commercial production. The first "Millionaire" was sold in 1893, with more than 5000 machines following over a period of almost forty years.

In 1913 Egli produced the first fully-automatic dividing machine, which was sold under the name MADAS (from Multiplication, Automatic Division, Addition, and Subtraction). The MADAS was a based on the slide-set Thomas Arithmometer, with an internal programming mechanism to perform the division algorithm.

Both the Millionaire and the MADAS continued to develop during the 1920s, with the addition of various keyboard setting mechanisms and (external) electric motor drives. A multiplier setting keyboard was added to the Millionaire as late as 1927.

In 1931 the MADAS was re-designed into a more modern form in the style of the American Monroe machines. The "MADAS Portable" was the first of a line of full-keyboard rotary calculators which continued in production well into the 1960s. The top models included fully-automatic multiplication and division, automatic division setup, single-cycle back-transfer, and a triplex carriage with two accumulators.

The Egli mechanisms maintained a consistent style and quality over their 70-year development, with design concepts from the original Millionaire still clearly visible in the MADAS of the 1960s. Follow the links above for detailed technical descriptions.

The Millionaire

The "Millionaire" was the first commercially-succesful machine to perform multiplication directly rather than by repeated addition. Over 5000 machines were built by engineer Hans W Egli in Zurich, from the 1890s to the 1930s.

The "Millionaire" contained a representation of the multiplication table from 1 x 1 to 9 x 9, in the form of pins of varying length set into a block of brass (what we would now call a "read-only memory"). The table allowed the machine to perform a multiplication with just a single turn of the crank for each digit of the multiplier.

The machines were unsurpassed for rapid and reliable multiplication, and were widely used in the banking, insurance, transport, and mining industries. They were eventually overtaken by the development of fully-automatic rotary calculators in the early 1930s.

Please refer to the Technical Section for a detailed description of the Millionaire mechanism, and a Register showing the extensive range of still-extant machines.

Millionaire (9kb) "Millionaire" Calculating Machine, S/N 2789
Technology: Rack and pinion, direct multiplication, slide-set, manual
Digits: 8 setting, 8 counter, 16 accumulator
Dimensions: 470W x 310D x 195H
Weight: 33 kg
Manufactured: Zurich, Switzerland, 1893-1930s

The most common version of the Millionaire is a manually-operated slide-set machine in a wooden case. The brass top panels of the machine were originally finished with a chemical blackening, which has usually worn through in the areas of greatest contact (although in this machine it has disappeared entirely).

To perform a multiplication, the first factor is set up on the sliders at the top centre of the machine. The most significant digit of the second factor is set on the multiplier lever at the left, and the crank at the right is given one full turn. The carriage moves automatically to the next position, the operator sets the second digit on the multiplier lever, and the process is repeated as required. The result appears on the register across the centre of the machine.

Millionaire with keyboard (9kb) "Millionaire" Calculating Machine, S/N 2968
Technology: Rack and pinion, direct multiplication, key-set, motor drive
Digits: 8 keyboard, 8 counter, 16 accumulator
Dimensions: 470W x 310D x 195H
Weight: 33 kg
Manufactured: Switzerland, 1913-1930s

Although excelling in its primary task of multiplication, the Millionaire's slider setting mechanism was too slow to be useful in adding long columns of figures. The provision of an optional keyboard (1913) and an electric motor drive (1911) attempted to make the machine more practical for other types of calculations.

The machine illustrated has an 8-column keyboard with manual or automatic clearing. The heavy-duty motor and gearbox are mounted externally under the baseplate, requiring the machine to be mounted on a tubular metal frame with an open top. The enclosed wooden case was replaced with a set of aluminium side panels and a painted sheet-metal cover.


The MADAS of 1913 was the first calculating machine with fully automatic division. The stepped-drum mechanism follows the general style of the Thomas Arithmometer, with extensions developed by engineer Erwin Jahnz of Zurich. Jahnz had previously worked on pinwheel machines at Brunsviga.

The machine improves on the Arithmometer by providing a quick-clearing mechanism for the setting slides, and separate controls for single-step and continuous carriage movement. The registers have a "neutral" position so that the carriage can be moved without lifting. However the main feature of the Madas is the division programming mechanism, which controls the sequence of subtractions, additions, and carriage shifts to complete a fully-automatic division.

The top panel of the machine lists a single US Patent issued to Jahnz on December 16, 1913 (No 1081310), which relates only to the register drive mechanism. The division mechanism is described in his German patent (DE277829) of 20 September 1912.

MADAS No 3527 (8kb) MADAS, S/N 3527
Technology: Stepped drum, slide set.
Digits: 7 setting, 7 counter, 12 accumulator
Dimensions: 490W x 195D x 150H
Weight: 12.5 kg
Manufactured: Zurich, Switzerland, 1913-1930s

This 7x7x12 machine is the smallest of the MADAS range. The casing is of cast iron, with legs at the back to raise the control panel to a convenient angle, and a clip-on sheet-metal cover. The carriage with the accumulator and counter registers is mounted at the top of the machine, with clearing sliders at the right-hand end. Two levers at the top left allow the carriage to be moved continuously or one step at a time. A lever at the front left reverses the registers for subtraction, and another at front centre returns the sliders to zero. The winding handle at the front right must be pressed down to engage the registers before turning.

The machine can be used for addition, subtraction, and multiplication in the same manner as with the Arithmometer. Division is set up manually with the carriage at the far right. The division control (below the bell) is then set to the left, and the crank is pressed down and turned continuously until the bell rings twice. The sequence of subtractions, additions, and carriage shifts is completed automatically, leaving the result in the counter register.

MADAS No 3775 (8kb) MADAS, S/N 3775
Technology: Stepped drum, slide set.
Digits: 8 setting, 9 counter, 16 accumulator
Dimensions: 605W x 195D x 150H
Weight: 16.8 kg
Manufactured: Zurich, Switzerland, 1913-1930s

A larger MADAS in 8 x 9 x 16 format, but otherwise identical to the previous model. Several different configurations were available, including a machine for Sterling currency. Later models provided optional keyboards, motor drives, and automatic multiplier mechanisms.

The MADAS Portable

MADAS shield The MADAS Portable from 1931 was designed from the outset as a full-keyboard fully-automatic machine, building on Egli's previous experience with the Millionaire and the "long" MADAS.

The A and (later) B series Portables were 10-column machines with fully-automatic multiplication and division, including automatic carriage positioning and register clearing. A semi-automatic L series provided automatic division but deleted the automatic multiplier. Simpler non-automatic models were available in both hand-cranked and motor-driven versions. All of the Portable machines used the same basic calculating mechanism, with the addition of various combinations of features and optional extras.

The Madas mechanism was very solidly built, with the motor-driven machines operating at 440 cycles per minute (over 7 cycles per second). The basic design continued in production, with only gradual changes, from the Portable of 1931 to the BTG of the late 1960s. An illustrated description of the Portable mechanism is available in the Technical Section.

The Madas shield (above) shows a device which is often taken to be a knight's helmet or some similar item of mediaeval equipment. It is actually an engineering drawing of a stepped-drum assembly from the new actuator mechanism. The shield logo was used in various forms until the end of production.

Fully-automatic Portables

Madas Model 20AZV (8kb) MADAS Model 20AZV, S/N 35888
Technology: Stepped drum, fully automatic
Digits: 10 keyboard, 10 counter, 20 accumulator
Dimensions: Body 250W x 320D x 220H, carriage width 360mm
Weight: 14.8 kg
Manufactured: Zurich, Switzerland, 1930s-40s

The Madas Portables are full-keyboard machines based on a very compact version of the stepped-drum mechanism from the earlier Madas. The main mechanism is contained in the upper section of the body, which is only about 90mm high. This section sits on a sloping cast-aluminium base, with two legs at the rear to raise the keyboard to about 30°. The base is mostly open at the sides and the rear, with the motor mounted underneath. The carriage travels across the top rear of the machine.

The A-series machines have powered carriage shifts and powered register clearing. The keyboard has a setting check dial, with Repeat and clearing keys on the left-hand side. The main accumulator has "twirlers" to allow values (such as dividends) to be set directly, and some models have a split clearing mechanism. The accumulator tens carry normally extends to 12 places, but the Z in the model number indicates that this machine is fitted with an extended carry mechanism which operates across all 20 places. The 10-digit counter register has full tens carry, with automatic and manual reversing.

Addition and subtraction operate in the normal manner. To perform a division, the operator sets the dividend on the keyboard and presses the "Division Set-up" key at the upper left. This automatically clears the accumulator, positions the carriage, transfers the dividend from the keyboard, and clears the keyboard and counter. The operator then enters the divisor on the keyboard and presses the Divide key at the upper right. The division proceeds automatically to completion, or until the Stop key is pressed.

The A-series machines all include a fully-automatic multiplier mechanism, accessed through a special 10-digit multiplier register at the front of the machine. Values can be entered into the multiplier from the keyboard or from the back-transfer mechanism, or directly from the twirler knobs at the front. Controls are provided to either clear or retain the multiplier setting after use, or to subtract the product from a value already in the accumulator ("negative multiplication").

To perform a normal multiplication, the operator enters the first factor on the keyboard. A press of the wide "multiplier bar" at the front of the machine transfers the number to the multiplier register in a single machine cycle. The second factor is entered on the keyboard, and the same multiplier bar is pressed again. The mechanism performs the necessary additions and carriage shifts, then (optionally) clears the multiplier and returns the carriage to its home position. A back-transfer key at the left of the keyboard can transfer the result back to the multiplier register in a single machine cycle for re-use in a further calculation.

The use of the same keyboard and control bar for both factors provides an efficient "short-cut" method for calculating squares - enter the number, hold the Repeat key to retain the keyboard setting, and press the multiplier bar twice.

The knob on the right of the machine can be replaced by a crank so that the machine can be operated by hand when necessary. The motor is automatically disconnected by a centrifugal clutch when it is stationary.
Early "Madas Portable" rear panel label
Madas 20AZV rear panel label
Madas 20AV "Toplodiv" flier (late 1940s)
Madas 20AT "Tripolo" flier (late 1940s)

Madas 20ATG (8kb) MADAS Model 20ATG, S/N 70052
Technology: Stepped drum, fully automatic.
Digits: 10 keyboard, 2x10 counter, 2x20 accumulator
Dimensions: Body 240W x 305D x 230H, carriage width 380mm
Weight: 17.2 kg
Manufactured: Zurich, Switzerland, 1940s-50s

The Madas styling was updated in around 1950 with new moulded keytops and a grey-and-green colour scheme. The lower section of the case has been enclosed at the sides and the back, so that the motor and electricals are fully protected. There were only minor changes to the mechanism.

This Model 20ATG from the 1950s is a fully-automatic machine fitted with a very elaborate "triplex" carriage.

The carriage adds a second counter register with selective clearing (but no tens transmission), and a second 20-digit accumulator register. The tens-carry mechanism for the second accumulator is contained entirely within the carriage, and is driven by a full-width camshaft and a long "drum gear" at the back of the machine. The second accumulator can be engaged or disengaged independently, in either direct or complement mode, to accumulate running totals and intermediate results. The register is cleared manually via the thumb lever at the upper right.

The machine as a whole displays a total of eighty numerals - 20+20+10+10 on the carriage, 10 on the keyboard register, and 10 on the multiplier.

Madas 20BTG MADAS Model 20BTG, S/N 94046
Technology: Stepped drum, fully automatic.
Digits: 10 keyboard, 2x10 counter, 2x20 accumulator
Dimensions: Body 240W x 305D x 230H, carriage width 380mm
Weight: 17.6 kg
Manufactured: Zurich, Switzerland, 1950s-60s

The only external difference between the fully-automatic A and B-series machines is in the "negative multiplication" control. The small "+/-" multiplication lever at the bottom left of the A-series keyboard has been promoted to become an extension at the left of the multiplier bar, so that both can be pressed together.

There were more significant changes internally, with the addition of power-assisted mechanisms to provide a lighter touch for the multiplier bar and the division setup key. The B series also included a number of new interlocks between the function keys to prevent mis-operation.

The machine illustrated 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 performing a series of squares (as in statistical calculations). On the right is a similar lever marked with a square root symbol. This does not perform a full automatic square root, but simply modifies the operation of the Division key to assist in performing the manual square root algorithm.

Madas 20BTG MADAS Model 20BTG, S/N 96214
Technology: Stepped drum, fully automatic.
Digits: 10 keyboard, 2x10 counter, 2x20 accumulator
Dimensions: Body 240W x 305D x 230H, carriage width 380mm
Weight: 17.6 kg
Manufactured: Zurich, Switzerland, 1950s-60s

This late-model BTG is identical to the previous example, except that the Negative Multiplication bar is finished in red. (The multilier bars are not just painted, but are coated in vitreous enamel).

The small 4-digit counter at the front left-hand corner is another optional extra which records the number of multiplications performed (again useful in statistical work). The counter is reset manually by the knob at its left.

Madas Model 20BS (8kb) MADAS Model 20BS, S/N 85531
Technology: Stepped drum, fully automatic
Digits: 10 keyboard, 10 counter, 20 accumulator
Dimensions: Body 250W x 320D x 215H, carriage width 360mm
Weight: 16.5 kg
Manufactured: Zurich, Switzerland, 1950s-60s

Model 20BS is another fully-automatic B-series machine with power-assisted setup controls. The carriage has only a single counter and accumulator, but includes a push-button tabulator mechanism.

The special feature of this machine is a simple and ingenious mechanism to assist in ongoing calculations involving division.

The normal division algorithm requires the result to be copied manually from the counter register in order to be re-used in an ongoing calculation. Model 20BS has a small lever at the left of the carriage, which allows a pawl on the left of the counter drive mechanism to engage with the main accumulator. The count is replicated at the left of the accumulator as the dividend is reduced at the right. The result can be re-used immediately in a following division, or it can be back-transferred to the front register for a multiplication.

Semi-automatic Portables

Madas Portable 1930s (8kb) MADAS "Portable" Model 20L, S/N 31829
Technology: Stepped drum, automatic division.
Digits: 10 keyboard, 10 counter, 20 accumulator
Dimensions: Body 250W x 300D x 210H, carriage width 355mm
Weight: 11.8 kg
Manufactured: Zurich, Switzerland, 1930s

This early L-series Portable from the 1930s provides "semi-automatic" division but no automatic multiplication. Division must be set up manually, but then proceeds automatically to completion on depression of the red Division key at the upper right. The 20L has an electric motor drive with powered carriage shifts and register clearing, but can be operated manually when necessary by fitting a crank to the angled drive shaft on the right of the machine. The motor is automatically disconnected by a centrifugal clutch when stationary. The extended drive shaft was deleted on later machines, but the interchangeable knob and crank remained.
Early "Madas Portable" rear panel label

Madas Model 20LZS (8kb) MADAS Model 20LZS, S/N 97841
Technology: Stepped drum, automatic division
Digits: 10 keyboard, 10 counter, 20 accumulator
Dimensions: Body 250W x 300D x 215H, carriage width 360mm
Weight: 13.9 kg
Manufactured: Zurich, Switzerland, 1950s-60s

This Model 20LZS from the 1960s is generally similar to the 20L above, but with the addition of a push-button carriage tabulator, an extended carry mechanism on the main accumulator, and the automatic division setup function from the fully-automatic A series.

Basic Portables

Madas Model 16eN MADAS Model 16eN, S/N 91144
Technology: Stepped drum, power-assisted division
Digits: 8 keyboard, 8 counter, 16 accumulator
Dimensions: Body 215W x 290D x 200H, carriage width 300mm
Weight: 9.2 kg
Manufactured: Zurich, Switzerland, 1950s-60s

The Madas range included several basic models in both hand-cranked and motor-driven varieties. This Model 16eN is an 8-column electric machine, but the motor only drives the adding mechanism. Register clearing is done manually by the two sliders at the right of the carriage, using the same mechanism as in the Millionaire and the long Madas. The carriage is spring-loaded towards the left by a typewriter-style spring barrel, and can be moved one step at a time by the Left Shift key at the right front. It can be returned in steps by the lever to the right of the Add key, or fully by hand pressure. The keyboard setting check is provided by means of numbers painted on the front faces of the keys, which only become visible when the key in front is depressed. The illustration shows "123" set at the left of the keyboard.

The 16eN has a peculiar method of power-assisted division. After setting up a division in the normal manner, the operator switches the small Add/Sub and Div levers at the upper right, and then presses the Plus key. The machine subtracts until underflow and then stops. Pressing the Minus key restores the underflow and releases the carriage, which steps to the left by spring power. The operator then repeats the Plus and Minus keystokes until the division is completed. The use of the Plus key to subtract is a carry-over from earlier models, which had only a single Plus/Minus key and the Add/Sub reversing lever. It is still necessary in the 16eN because the counter register can not be reversed independently.

Resources for further information

Original text and images Copyright © John Wolff 2002-15.
Last Updated: 14 March 2016

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