# Unitas

My Unitas
Video
Stepped drum
The TIM calculator
The Unitas Calculator
Model variations
Books and Manuals
Patents

## My Unitas

It has an 8-digit input register at the front which uses sliders for each digit. The two carriages have 12-digit output registers, and there is a 7-digit revolution counter in the bottom carriage.

There are several serial numbers. The inner frame is stamped at the front-right with the number 03117. The top carriage has the number 03110 stamped in its side at the front-right, and similarly the top carriage has 03096. However they all also have a shared serial number 2014. This number is stamped underneath each carriage, at the far left of the inner frame, and also on the inside of the front cover of the case. I suspect that this machine was made somewhere between 1910 and 1914.

It came with the metal protective cover. This cover is in poor condition, because it has a small lock but no key, and it has at one time been forced open. This has also caused the seams on the left side of the cover to come apart.

The carriages can be easily detached. On the right hand side the rail under the carriage ends with a small crosswise stopper that can be rotated parallel to the rail, after which the whole carriage can slide off to the left. The front cover is held in place by four knobs that can be twisted to release it.

## Video

Here is a video where I demonstrate the Unitas.

## Stepped drum

As long ago as 1672, Gottfried Wilhelm Leibniz invented the stepped drum mechanism for use in a calculating machine. At the time this was very hard to manufacture as everything was made by hand, but a working machine was completed in 1694. A stepped drum is a rotating cylinder that has long gear teeth like ridges of varying size along its length. There is a gear that engages with it, and it can be moved to ten different positions along the length of the drum. Depending on the position of this gear, it will engage with any number of the drum's teeth from 0 to 9. In this way the 1-digit input of a slider is converted to a rotation by the required amount.

Thomas de Colmar designed a better machine based on this mechanism, getting patents in 1820, 1850, and 1865, and began to commercially produce his Arithmometer in relatively low numbers in 1851. These early Arithmometers are still exceptionally rare and expensive. His son developed them further in an 1880 patent, and with improvements in production methods these were made in much larger numbers. In germany, Arthur Burkhardt produced an Arithmometer clone from 1878, and many other companies followed.

The Arithmometer-type stepped drum calculators are relatively large, heavy, and cumbersome to use compared to Odhner-type pinwheel machines so they eventually began to fall out of favour. Despite the stepped drum's reputation for being bulky, the smallest mechanical calculator, the Curta, is also a kind of stepped drum machine but it can be small because it manages to use only one drum shared by all the digits instead of each digit having its own drum.

## The TIM calculator

The TIM ("Time Is Money") calculator is a stepped drum calculator based on the Thomas Arithmometer. It was made by Ludwig Spitz & Co. in Germany from 1907 until about 1940.

It has an input register at the front which uses sliders for each digit. It has a carriage containing an output register and a revolution counter. There is a crank to the right of the input sliders, and each turn of that crank will normally add the input to the registers, and increment one digit of the revolution counter. The carriage can be moved by hand directly, through using the large knob on the left hand side to tilt the carriage up, slide it, and drop it into a new position. This allows you to add the input to higher order digits of the output register, which is part of multiplication. To the left of the input sliders is a lever that switches between addition and subtraction. In subtraction mode a turn of the crank subtracts the input from the register and decreases a digit of the revolution counter.

Note that the output register in the carriage does not have a built-in carry mechanism. Instead, the carries are performed by the mechanism in the body of the machine. This means that when the carriage sticks out to the left of the machine, those leftmost digits of the register cannot be affected by a turn of the crank. This is usually not a problem. If a carry occurs from the leftmost place of the mechanism, a warning bell rings. The revolution counter has no carry mechanism at all. Each digit wheel can move forward from zero to show the black digits 1 to 9, or move backward by subtraction to show the red digits 1 to 9.

There are two sliders on the right hand end of the carriage which are used to clear the output register and revolution counter. You have to tilt the carriage to disengage it from the mechanism, and then push one or both of the sliders to the right. There is a clearing lever below each digit of the input register. If you push one of those levers down, the corresponding digit and all the digits to its left are cleared. If you push a clearing lever up, then the corresponding digit and all the digits to its right are cleared.

## The Unitas Calculator

The Unitas is the bigger brother of the TIM, in that it has an additional carriage above the first which provides a second output register. This carriage is the same length as the first carriage but narrower because it has no revolution counter. The knob that you use to move the first carriage is attached to a rod that can connect the two carriages together so that they can both be moved at the same time by the same amount.

The switch lever for selecting addition/subtraction is split in two. Usually they are connected together so that both registers behave in the same way, adding to both or subtracting from both. The most obvious reason to use the extra register in this way is to keep track of subtotals. If you disconnect the smaller lever and put it in the middle position, then the two registers behave in opposite ways - adding to one and subtracting from the other.

## Model variations

At first the TIM and Unitas calculators were mounted inside a wooden case, just like almost all Arithmometers had been before it. In 1909 they switched to a metal case (and incidentally, so did Burkhardt). A year later they added the input clearing levers, and changed to a more rounded metal case with an easily removable front cover.

From 1914 there were versions with a full keyboard input instead of sliders. By that time electrically driven versions were produced as well, which were very large and heavy, and almost twice as expensive. The electric machines no longer needed a crank, but they still had the crank axle to which a handle could be attached in case the motor broke. These detachable handles also began to be used on the manual machines, even though they don't really need the handles to be so easily detachable.

Production continued probably until the second world war, and there seem to be no further major changes to the TIM and Unitas mechanisms during that time. There was a little variation in the casing, and in the 1930s a travel version was made that had a smaller case and fold-out legs.

Each of the above versions were produced with various sizes of the input and output registers. These size variations were denoted by the Roman numerals I to V.

ModelInputCounterOutput
I 6 5 8
6 7 10
7 7 10
7 7 12
II 8 7 12
III8 9 16
IV 109 16
V 101120

Ludwig Spitz also produced a listing-adding machine called the TIM-Add. It seems it was not commercially successful.

## Books and Manuals

Manual Of Mechanical Calculation By Means Of the Calculating Machine "UNITAS"     (PDF, 25.1 MB or archive.org)
1915?
Ludwig Spitz & Co. G.m.b.H.
69 page booklet
160mm × 239mm × 4mm

This is the English language manual for the Unitas calculator. There is no copyright year. A small piece of paper has been glued in to explain the use of the keyboard. As keyboards were introduced in about 1914, I assume this manual is from around that time. It also contains a section with various useful lookup tables, and a section with exercises.

Here are some advertisements that I found in online archives of newspapers and magazines. In the USA it appears that the sole importer was Oscar Müller.

There were also many wanted ads, for personnel to work in the facatory and its offices, but also for materials.

Here are various notices about the company and changes to its personnel.

Here are a few articles about the company or its calculators. The last item is a Dutch article describing a lecture given by Ludwig Spitz in Austria about the importance of salesmanship.

Here is the entry for the TIM and Unitas machines in Illustriertes Orga-Handbuch erprobter Büromaschinen by Ludwig Brauner and Victor Vogt from 1921.

There are entries for the TIM and Unitas machines in Ernst Martin's book, Die Rechenmaschinen. Also included is the entry for the Tim-Add, a short-lived listing-adding machine.

Lastly, here are the entries for the TIM, Unitas, and Tim-Add machines in Organisations-Lexikon by Walter le Coutre and Walter Thoms from 1930.

## Patents

Ludwig Spitz & Co filed many patents for calculating machines, of which several seem to be for machines that were never brought into production. Here are the patents I found that apply to the TIM and Unitas. While all the German and Austrian patents are assigned to Spitz or his company, in other countries they were often assigned to Robert Rein.

PatentFiling datePublish dateNameDescription
DE 216,56102-06-190624-11-1909Ludwig SpitzUnitas calculator
DE 184,98416-06-190615-05-1907Ludwig SpitzInput slider clicking mechanism
DE 219,55710-08-190602-03-1910Ludwig SpitzUnitas carriage knob
AT 42,653B03-10-190625-06-1910Ludwig Spitz & CoUnitas calculator
DE 229,56926-01-190729-12-1910Ludwig SpitzUnitas add/sub switch mechanism
DE 202,13729-08-190729-09-1908Ludwig Spitz & CoGear lock/release mechanism
DE 202,138 & DE 203,15109-11-190729-09-1908 / 15-10-1908Ludwig SpitzCarry mechanism
DE 208,16828-02-190818-03-1909Ludwig Spitz & CoRemovable carriage
AT 38,474B24-08-190825-08-1909Ludwig Spitz & CoDecimal point indicator
DE 218,14621-10-190822-01-1910Ludwig Spitz & CoInput clearing mechanism
DE 217,04707-02-190917-12-1909Ludwig Spitz & CoCarry mechanism
DE 227,71519-08-190927-10-1910Ludwig Spitz & CoElectric motor drive mechanism
AT 45,081B13-10-190925-11-1910Ludwig Spitz & CoRemovable front plate
AT 45,082B13-10-190925-11-1910Ludwig Spitz & CoCrank drive mechanism
AT 45,080B13-10-190925-11-1910Ludwig Spitz & CoAdd/sub switch mechanism
DE 247,42325-01-191129-05-1912Ludwig Spitz & CoUnitas add/sub switch improvement
AT 66,783B19-08-191210-08-1914Ludwig Spitz & CoOverflow warning bell
AT 75,609B30-06-191325-02-1919Ludwig Spitz & CoKeyboard input