CURTA

The universal pocket
calculating machine.
System C. Herzstark
Weight 230 gr.
CONTINA S.A. Mauren/Liechtenstein
For the exact time:
the pocket watch ...
For taking pictures:
the miniature camera...
FOR CALCULATIONS:
THE CURTA
high precision pocket calculating machine,
performing the four arithmetic operations.

Contina S.A. launches a novelty: the universal pocket calculating machine, robust and efficient. It is a high precision item, constructed according to the principles of fine-mechanical mass production and with the experience of several decades provided by the designer C. Herzstark specializing in the construction of calculating machines.

The picture above shows that the dimensions of this machine are extremely small. One can easily hold it in one hand or put it in ones pocket without any inconvenience. It answers to the long term demand by calculators who wished a less cumbersome machine that could be used anywhere, and it therefore fills a niche that has always existed for calculating machines.

The Curta is the indispensable aid for traveling merchants, the building contractor on the construction site, the technician in his workshop, the designer at his drawing board, the scientist in his lab, and the student. Every place where the use of a noisy machine would be intolerable and where it isn't possible or practical to bring a heavy and cumbersome machine, like during surveying, the eminent qualities of the CURTA render it indispensable. In commercial or technical offices, in banks and administrative offices as well as behind the counter, the CURTA is especially appreciated for its easy handling. In fact, until now it was not possible for an operator to use his machine directly on his writing pad. Therefore he paid the extra effort of numerous movements of his body, his hands, his head and his eyes, to and from his writing pad and the calculating machine. The advantages of the Curta have gained it the approval without reserve of professionals, and a considerable demand for it from all over the world.
With the Curta a high precision calculating machine has been realized that equals the universal hand driven machines, millions of which are spread all over the world. According to more than one report the Curta is superior to many of them, most notably by its simplicity and convenient operation.

The Curta equals
the universal machines described above in:

Its calculation functionalities
Curta adds, subtracts, multiplies, divides, calculates squares, cubes, square roots. It enables the calculation of invoices, cubatures, percentages, interests, etc. ...
Its reliability
Curta posses mechanisms to prevent invalid operations and special mechanisms to avoid inertia-induced overshooting.
Its speed of calculation
Curta is a small machine. Its easy movement, the continuous carrying of tens on both counters and the single direction of rotation of the crank give it an exceptionally high operating speed.
Its good general layout
Curta has a horizontal line of windows for reading the setting The numbers on the counters are very clear because they are engraved and placed close to the surface.
Its quality
Curta is exclusively manufactured in mass production from selected metals and its high precision assures a complete interchangeability of parts.
Its longevity
Curta doesn't show any perceptible wear after years of use; thanks to the extremely reduced mass of the moving parts, it can endure millions of rotations.
The Curta is superior
over other machines in:

Its reduced size
Diameter max. 35 mm., height 85 mm.
Its low weight
About 230 gr., just a tiny fraction of the weight of the lightest machines with the same capacity produced nowadays.
Its capacity
8 setting digits, 6 digits in the counter, 11 digits in the result register, despite its small size.
Its elegance
due to its harmonic design and pleasing assembly of all its elements.
Its moderate price
enabled by high precision machining and a novel economical construction.
Its resistance against corrosion
Its silent operation
due to the small mass of the moving parts.
Its practical handling
Thanks to its insignificant weight, the smooth operating mechanism, the nicely rounded and well spaced setting knobs, the well legible digits on a matte background. It is important to note that for desk use, the Curta offers the very particular advantage of not forcing the operator to turn away from his writing to perform his calculations, as we will show now.
Fig. 1: Writing space = calculating space
Writing space and calculating space are in the same area. The picture above shows that during the calculation the Curta is held in the left hand, the machine is therefore directly above the writing space of the operator, i.e. in his field of view. The machine doesn't occupy any space on the desk because it is not placed on it, the left hand doesn't have to change its position during the recording of the result. So calculating and writing take place in the same working space.
The Curta is a four-function machine that an operator uses in one single working space.
Fig. 2: Writing space | calculating space
The writing space differs from the calculating space. The picture above illustrates the usual way of calculating with a fixed machine. In that case the writing space and the machine occupy distinct locations on the desk. Therefore writing and calculating take place in two different positions. Thus, the operator has to continuously move his body, his head, his eyes and hands from one working place to the other, which is clearly shown in the picture.
The Curta avoids that situation, and satisfies therefore in all respects the modern urge for control of strains and nervous stress at work.

Short description of the Curta
Fig. 3
The machine exists of a cylindrical body with a carriage containing the counter mechanisms mounted on top of it (see fig. 3).
On the body of the machine one finds the sliding knobs for setting of numbers. On the bottom are the movable decimal point indicators. The control digits of the setting register appear above each sliding knob. The operation is controlled by the crank. The carriage (see fig. 4) contains the mechanism of the revolution counter (set of digits in the clear segment) and of the totalisator (also called result register, set of digits in the black segment), movable decimal point indicators as well as the zero-setting mechanism with the retractable handle.

Fig. 4
The operation of the Curta resembles the operation of ordinary machines, except for the fact that the Curta doesn't have to be placed on a desk. To calculate one takes the machine in the left hand, placing the thumb and index finger on the grooved part of the carriage. This way one can lift the carriage and turn it in one direction or the other within the limits imposed by the revolution counter. Those limits are indicated by the arrow - the white one at the front of the body of the machine - that points to one of the numbers engraved at the lower edge of the carriage. If that arrow corresponds exactly with one of the numbers, the carriage rests in a notch and the machine is ready to operate.

The numbers (for example the numbers to be added, one of the two factors of the multiplication, or the divisor of the division) are set by means of the sliding knobs. It suffices to displace the knob corresponding to the unit of the digit desired (tens, hundreds, thousands) until that digit appears in the corresponding setting window.

Control of the number set is simple because all digits remain visible in a horizontal line in the setting windows.

The crank that drives the mechanism of the machine has a stop that can be felt easily, and helps in counting the number of revolutions during the calculation. When the crank is pulled or pushed along its axis, the mechanism moves between two positions, the lower one for augmentative calculations (adding, multiplication) and the upper one for diminutive calculations (subtraction, division). In both cases the crank has to be turned clockwise, a special stop preventing it from being turned in the opposite direction.

The revolution counter (digits in the clear segment) counts the number of revolutions made by the crank and indicates for addition the number of terms; for multiplication, the multiplier; for division, the quotient; for calculation of a root, the root. The revolution counter is operated on at the window corresponding to the position of the carriage indicated by the arrow.

The totalisator (digits in the black segment) indicates for addition, subtraction and multiplication, the result. For division, it indicates, depending on the calculation method used, the remainder or the dividend.

The continuous carrying of tens on both counters enables a considerable speed-up for many operations and reduces the number of revolutions of the crank (e.g. for multiplication using the 'simplified method'). It also enables the addition of multipliers (important for instance for cubatures, the calculation of interests etc. ...).

Setting the counters to zero is done by the handle with a ring (see fig. 3 and 4). It can be rotated in two directions. It has two, clearly indicated, stop positions where the clear segment borders the black one. Both counters can be set to zero in one movement, or each separately.

Fig. 5
The machine viewed
from the back
Reversing lever. When the reversing lever at the back of the machine (see fig. 5) is moved the direction of rotation of the revolution counter is reversed. When the lever is in its upper position (indicated by two arrow pointing in the same direction) both counters register numbers the same way. In the lower position (indicated by two arrow pointing in the opposite directions) the counters register numbers in two opposite ways.

Sample calculation. The numbers shown in figures 3 and 4 are those of the following multiplication: 645 432 x 63 992. The multiplicand can be seen in the control windows (fig. 3), the multiplier on the revolution counter and the product on the totalisator (fig. 4).

The time required for this calculation, including setting the numbers, is about 15 seconds with 29 revolutions of the crank. But if the simplified method of multiplication is used, made possible by the continuous carrying of tens, the time required is about 10 seconds, with only 13 revolution of the crank.

A division with a 6 digit quotient takes 30 seconds on average, including setting the numbers.

All other operations can be done in a minimum amount of time, using methods already known for ordinary machines.

The protective anti-shock case
of the Curta
View of the precision mechanism of the Curta
Fig. 6
View of the Curta without its hull
and with detached carriage.
Fig. 7
Schematic view of
the operation
of the Curta.
Fig. 7 shows that by means of the sliding knobs the setting gears are set in front of the toothed segment of the main drum of which the number of teeth corresponds to the input number. When the crank makes one revolution, the drum engages all setting gears successively. The rotation thus enforced on the setting gears is transmitted directly by the crown gears to the gears of the counters. For clarity, only one setting gear and transmission shaft is shown in fig. 7.

In the Curta subtraction is reduced to an addition by means of a vertical displacement of the stepped drum, that, when in its upper position, lets a complementary number of teeth engage with the setting gears. These simple operating principles enable a rational and robust construction, which ensures the reliability of the Curta.

Manufacturer:
CONTINA S.A.
Manufacturer of office and calculating machines
Mauren / Liechtenstein

Building I, Mauren
Building II, Eschen
For sale at:

Reproduction of texts and illustrations, even partial, is prohibited without our permission and without indication of the source.
Illustrations and descriptions can be subject to minor modifications.

34 51 6 f

Note: This should be 53 mm, see other brochure. (back)
This Curta brochure has been translated from the French version and converted to HTML by Andries de Man using a copy provided by Skip Godfrey, courtesy of Daniel Lewin. Thanks to Christophe Mery for assistance with the translation. See also an earlier version.

Andries de Man