Filotecnica Model 201 Back-Light Screen Projection Slide Rule, Italy c. 1955In the early 1950s thepany Filotecnica Salmoiraghi, well known for its precision equipment, developed a slide rule that projected the scales onto a backlit screen from the patents of Abeille and Aquilecchia. This solution allowed a verypact device to have the same precision as a traditional slide rule of 2.5 meters. With logarithmic calculators, precision is in fact proportional to length. - The goal was to market a logarithmic calculator cheaper than an electro-mechanical calculator. This aim was only partially achieved: the device is in fact very precise but was still too expensive. At the time of production, it sold for around the same price as a good motorcycle, and was the equivalent of two months’ average salary. It proved too expensive for individual professionals, whilepanies preferred to buy the more expensive, but tried and tested, Olivetti Tetractys. According to an article published in the journal of the Oughtred Society, the project was discontinued and only five units were built. - This example is one of the three known survivors, a fourth is in irreparable condition and nothing is known about the fifth. This unit is in excellent condition,plete with instructions in Italian and a probably non-factory leather case. The serial no. 45605 is typical of the factory, which numbered products in order of exit from the production line and not according to the series or model. No. 45605 appears among the four reported surviving instruments on the municationspany Telettra (one of the most important at the time) in 1955 but shows virtually no signs of use. Advertising for this calculator appears in the Filotecnica catalogs only in the years 1954 and 1955. Filotenica Salmoiraghi, founded in 1865 by lgnazio Porro - the inventor of prismatic binoculars, was the main Italian factory of optical, nautical, measurement and precision instruments for the best part of a century.Logarithmischer Projektions-Rechenschieber Filotecnica Modell 201, Italien, um 1955Anfang der 1950er Jahre entwickelte das für seine Präzisionsgeräte bekannte Unternehmen Filotecnica Salmoiraghi auf der Grundlage der Patente von Abeille und Aquilecchia einen Rechenschieber, der die Skalen auf einen hinterleuchteten Bildschirm projizierte. Diese Lösung ermöglichte, dass ein sehr kompaktes Gerät die gleiche Genauigkeit wie ein traditioneller Rechenschieber von 2,5 Metern Länge erreichte. Bei logarithmischen Taschenrechnern ist die Genauigkeit in der Tat proportional zur Länge. Ziel war es, eine logarithmische Rechenmaschine auf den Markt zu bringen, die billiger ist als eine elektromechanische Rechenmaschine. Dieses Ziel wurde nur teilweise erreicht: Das Gerät ist zwar sehr genau, war aber dennoch zu teuer, da es zum gleichen Preis wie ein gutes Motorrad verkauft wurde, was einem durchschnittlichen Gehalt von zwei Monaten entsprach. Zu teuer also für einzelne Kund