High-tech also plays a significant role at other Wiesbaden firms. The head office of SGL Carbon, the world's largest manufacturer of carbon fibre and graphite products, is to be found here. Vitronic Dr.-Ing. Stein Bildverarbeitungssysteme GmbH is an international leader in image-processing and a pioneer in toll systems components. Thus, high-tech from Wiesbaden is integrated into a modern German truck toll system throughout Germany and used daily at more than 1,000 sites. Wiesbaden is also the home of the German subsidiary of Abbott, a US pharmaceuticals company. This manufacturer of drugs, diagnostic and clinical products employs about 1,700 workers in the city borough of Delkenheim. Several companies have discovered Wiesbaden’s advantages in the logistics sector: The Dutch express services company TNT has built one of its largest distribution centres worldwide here and another company with an international reputation: Dow Corning. This company, which was founded in the USA in 1943, develops products and does research in the field of silicon technology and is now setting standards worldwide with currently more than 7,000 products and more than 5,000 active patents. A significant share of the investments made in Europe is allotted to Dow Corning GmbH in Wiesbaden.