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 and remains constant throughout the calculation. The first digit of the multiplier is set on the lever at the left, and the crank at the right is given one full turn. The process is repeated for the remaining digits. The result appears on the register across the centre of the machine.

Although excelling in multiplication and division calculations, 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) made the machine equally practical for all types of calculations.

The motor-driven machine was supplied on a tubular metal stand with the motor and gearbox mounted underneath. The wooden case was replaced with aluminium side panels and a painted sheet-metal cover.

This 7x7x12 machine is the smallest of the MADAS range. The casing is of cast iron, with legs at the back to raise the keyboard 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 slides 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 normal manner. 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.

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.

This machine is an early "L" series semi-automatic, with both an electric motor drive and provision for manual cranking.

The main mechanism of the Madas Portable is contained in the upper section of the case, 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. There is a manual drive shaft on a 45° bevel on the right of the machine, with a knob that can be replaced by a crank. The motor is disconnected by a centrifugal clutch when it is stationary, so that the machine can be cranked easily by hand.

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 has a split clearing mechanism. The accumulator tens carry extends to 12 places. The 10-digit counter register has full tens carry, with automatic and manual reversing. There is a (red) division setup key on the left of the machine, with the Divide and Stop keys on the right. The machine has powered carriage shifts and register clearing.
"Madas Portable" rear panel transfer (26kb)

The Madas A series includes a fully-automatic multiplier mechanism, accessed through an additional 10-digit register at the front of the machine. The multiplier register can be set from the keyboard or from the back-transfer mechanism, or directly from the twirlers. Controls are provided to clear or retain the 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 below. 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.

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 A-series machines have a back transfer key on the left-hand side, which moves a result from the accumulator back to the multiplier for re-use in a further calculation. The Z in the model number indicates that this machine is fitted with an extended tens-transfer mechanism in the main accumulator, which operates across all 20 places. A similar Model 20AT was fitted with a "triplex" carriage containing two ten-digit counters and two 20-digit accumulators.
Madas 20AZV rear panel label (16kb)
Madas 20AV "Toplodiv" flier (late 1940s) (30kb)
Madas 20AT "Tripolo" flier (late 1940s) (30kb)

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 is fully protected. There were only minor changes to the mechanism.

This Model 20LZS from the 1960s is similar to the 20L above, with the addition of a push-button carriage tabulator and an extended carry on the main accumulator.

The Model 20ATG from the 1950s is a fully-automatic machine fitted with the 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 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.

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

There were more significant changes internally, with the addition of a power-assisted mechanism to provide a lighter touch for the multiplier bar and the division setup key. The changes were mainly in the control mechanisms around the multiplier, and did not affect the calculating mechanism.

The B series also provided 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 calculating squares. On the right is a similar lever marked with a square root symbol. This does not perform an automatic square root calculation, but simply modifies the operation of the Division key to assist in performing the manual square root algorithm.

This late-model BTG is identical to the previous example, except that the Negative Multiplication bar is finished in red. (The 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. The counter is reset manually by the knob at the left.

Model 20BS is a fully-automatic B-series machine with power-assisted setup controls. The carriage has only a single counter and accumulator, and 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.