Soemtron History

Sömmerda coat of arms

The German "Rheinmetall" heavy engineering works was established by Heinrich Ehrhardt in Düsseldorf in 1889 as the "Rheinische Metallwaren und Maschinenfabrik Aktiengesellschaft" (Rhein Metalwares and Engine Works Corporation) and registered on May 7th 1889.  In the same year production started in rented accommodation in Dusseldorf's Talstrasse, and almost within a year they are employing 1,400 people producing 800,000 bullets a day.  In 1901 a munitions factory was then acquired in Sömmerda, a small town near Erfurt in Thuringia, Germany, on the Unstrut river.  Following the First World War the Sömmerda factory started producing office machines, typewriters, mechanical calculators, adding and listing machines, they continued to further develop their range of machines up to the Second World War in 1939-45.

Following the Second World War, the Sömmerda factory then found itself in the newly formed East Germany, with development and production now continuing as a state-run enterprise, but using the pre-war Rheinmetall name and logo.  In 1957, a group of young electronics engineers under the collective direction of Heinz Skolaude brought V.E.B.[1] Büromaschinenwerk[2] Sömmerda into the age of electronics.  In 1960 the name was changed to "Supermetall" and then later to "Soemtron" in 1962, when they exhibited at the Leipzig Fair of that year an electronic Fakturierautomaten[3] - the model EFA 380.  1963 saw the next model the EFA 381 with magnetic core memory.

The East German flag, no longer used

When the new brand name "Soemtron", composed from the words "SOEM"merda and Elek"TRON"ik, appeared, the long running legal dispute with the Düsseldorf Rheinmetall Group to the trademark "Rheinmetall" was resolved, along with use of the company logo and patent rights.  Previously to this, machines were sold under the trade name Supermetall.  In 1966 V.E.B. Büromaschinenwerk Sömmerda then released the first of three electronic calculators.  These models, with germanium transistors and Ferritkernspeichern[4], were produced in several versions - the ETR 220, the ETR 222 (which entered production in 1968), and the ETR 224 (also in 1968).  From 1968 onwards electronic invoicing and accounting systems were introduced including the EAA 382 and EAA 385 systems, and in 1971 they began production of printers.  All production of mechanical calculators ceased at the factory in 1967 with the firm moving over to full production of electronic calculators, mainframe and personal computers like the 8-bit computer model 1715 and latterly the Soemtron 286 and 486 PC's right up until they finally ceased all production in December 1991 having failed for many years to keep up with the western world's dramatic advancements in electronics and computing.

With production of around one million computers, calculators and office machines, V.E.B. Büromaschinenwerk Sömmerda was probably the largest manufacturer of mechanical and electronic computing technology in the eastern Bloc.  Much of the information summarized here originates from a book by Annegret Schule, "BWS Sömmerda" (Desotron Erfurt 1995 ISBN 39-8039-311-9), which describes the history of the enterprise in some detail.  Further information and numerous photos of the different Rheinmetall-Soemtron models can be found in a book by Alfred Waize, "Die Welt der Rechenmaschinen" - "The world of the Calculating Machines" (Desotron Erfurt 1999 ISBN 39-3287-509-5).

Manufactured from 1966 to 1977 by V.E.B. Büromaschinenwerk Sömmerda, the Soemtron ETR series of calculators are by modern standards very basic six and seven function calculators with a 15 digit Nixie tube display or mechanical print mechanism.  Three different units (possibly four) were produced in the eleven year production run of these increasingly rare early electronic calculators from the Eastern Bloc.

  • The ETR 220 - with six functions and three temporary registers, it is the most common machine in the range even today, with over 155,000 produced by V.E.B. Büromaschinenwerk Sömmerda in the 11 years of production between 1966 and 1977.  Technical information for the 220 is rare but manuals, circuits and information in several languages do turn up from time to time, as do a number of 220's in various conditions from our fist unit that was missing a power supply and its case, to fully functioning units.  Recent 220 units on a well known auction site (2015) have been appearing for very high, almost ludicrous amounts (£1500 - €1800).
  • The ETR 222 - with six functions and again three temporary registers, just over 3,203 type 222 calculators were manufactured between 1970 and 1972, this machine is rarely seen on the open market, and to date no documentation for the 222 has been found.  Like the 224 (below) only four 222's are known to exist, and only one has come up for sale in recent years, and we bought it ! (€130).
  • The ETR 224 - a very, very rare machine with only 526 units manufactured in the six year production run from 1968-1974.  The 15 digit nixie display of the 220 and 222 is replaced with an 18 coloumn 16 digit mechanical printer mechanism (15 digits + decimal point + 2 signs).  The Soemtron 224 electronics appears to be based on a heavily modified version of the 222 calculator, with additional control electronics for the printer.  It would seem that no technical information now exists for the 224 at all, and only four machines are known to exist in the wild, including the partially working example in the Sömmerda Historisch-technisches Museum im Dreyse-Haus Weißenseer, Sömmerda.

Rumours continue to surface about the existence of a fourth ETR type, an ETR 221 which was another printing variant like the 224 but split into two housings with a long umbilical cable, this machine was a predecessor to the 224 and ended up being the 224 prototype.  One of these 221 machines apparently existed in London at the offices of the UK importers Office and Electronic Machines Ltd. (OEM Ltd.)[5].  Further information about the 221 can be found on the 221 page from the menu links above.

Logo from a Soemtron ETR 220

The Soemtron series of calculators were imported into the U.K. from the D.D.R. by "Office and Electronic Machines Ltd. (OEM Ltd.)", but with the advent of small calculators using logic chips or basic processors during the eleven year production run of the Soemtrons, their sales market and use was restricted mainly to Eastern Bloc countries.

In Film -
Several Soemtron ETR 220 calculators appeared in a 1977 Russian film - "Office Romance" directed by Eldar Ryazanov.  Stills from the film showing the Soemtron's can be viewed at Sergei Frolov's website, there is also a Wikipedia entry for the film.

Legal -
We have a copy of an export permit that Bernard Green of Office and Electronic Machines Ltd. (OEM Ltd.) used in 1967 to export various manuals and documentation from East Germany.

In 1959 and 1960 Walter Kasper of VEB Elektronische Rechenmaschinen Wissenschaftlicher Industriebetrieb Karl-Marx-Stadt, as the inventor, applied for patents in Germany, France, England and Holland for a "Calculating Device" for the serial addition or subtraction of two binary numbers with BCD correction.  The patents are - (with date filed / date granted) -

1 Germany DE1099767B (January 1959 / February 1961) - Rechenwerk - a calculating device.
2 France FR1251613A (May 1960 / December 1960) - Mècanisme de calcul pour l'addition et la soustraction de deux nombres dècimaux - Calculation mechanism for the addition and the subtraction of two decimal numbers.
3 England GB924164A (November 1959 / April 1963) - A Calculating Device.
4 Holland NL235929A (February 1959 / March 1964) - Rekeninrichting - Computing apparatus, documents not available.
5 Holland NL244711A (October 1959 / April 1964) - Rekeninrichting - Computing apparatus, documents not available.

Advertising -
Bernard Green has sent in a copy of an advert that appeared in "Office Methods and Machines" July 1967, as a "New desk calculator with 15 digit capacity and three independent accumulators".

Soemtron logo of unknown origin

The Soemtron 220 range also appeared in the "Büromaschinen Lexikon", a German technical publication covering office machinery and related products.  Soemtron branded products appeared in all the issues between 1962 and 1969 but only three entries are available online below -

1 The index page for the Büromaschinen Lexikon
2 A Soemtron 220, and a 221 with integral printer 1966-67 (Click "Soemtron")
3 A Soemtron 220, and a version with printer 1967-68 (Click "Soemtron")
4 Description for the Soemtron 220 and a "fast printer, click
the "Sumlock" link to see photos and pricing for the 220
and 224
1968-69 ("Soemtron" & "Sumlock")

Personal -
We have started a small section here for personal thoughts and recollections of Sömmerda, the Soemtron brand and its people.  To kick this section off the first is from Bernard Green who was Senior Engineer at Office and Electronic Machines Ltd. (OEM Ltd.) in London UK, importers / exporters of the Soemtron series calculators.  Has sent us his recollections of his time at the factory and its influence.

Alternative Soemtron logo

If you have any further historical information, circuits, drawings, photographs, data or manuals about the Soemtron ETR 220, 221, 222, 224 or their manufacture, test equipment (Prüfgeräte) or you just know more about the Soemtron companies in general then please let us know, contact us.

Some of the information on this page has been derived from www.robotrontechnik.de with grateful thanks.


1 Wikipedia entry for V.E.B. = Volks Eigener Betrieb, or Peoples Owned Company V.E.B.
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2 Büromaschinenwerk. Office Machine Works.
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3 Fakturierautomaten Automatic Invoicing.
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4 Ferritkernspeichern Ferrite Core Memory.
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5 OEM Ltd. Office and Electronic Machines Ltd., 140-154, Borough High Street, London, SE1 1LH.  Marketing company for mechanical desk calculators.  "Distributors for the United Kingdom and Republic of Ireland of Adler, Triumph, and Imperial typewriters, calculators, invoicing, accounting, word processing machines, and other office equipment and machines."  (Text from an advert placed by OEM Ltd, in the Glasgow Herald of the 11th June 1973

They were also known at various times as - O.E.M. (Systems Furniture) Ltd. (#01396792), O.E.M. Orion Ltd. (#01666907), O.E.M. Orion (#1179756).  They appeared to have petitioned for the winding up of several other companies as their creditors in 1979 and 1982[back] [top]

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