The Physikalisch-Technische Bundesanstalt (PTB) is based in Braunschweig (Brunswick) and Berlin. It is the national institute for natural and engineering sciences and the highest technical authority for metrology and physical safety engineering in Germany. Part of its brief is the accurate measurement of time. It is responsible for four German caesium atomic clocks, CS1, CS2, CSF1 and CSF2, and the longwave time signal DCF77. In addition, the PTB operates time servers for the distribution of time on the internet. They are also responsible for the certification of voting machines for the German federal and European elections. The PTB was originally founded in 1887 as the Physikalisch-Technische Reichsanstalt (PTR) (the Physical and Technical Institute of the German Reich). The goal of the organization was supervising and directing calibration and establishing metrological standards. Research areas included spectroscopy, photometry, electrical engineering, and cryogenics. Werner von Siemens was instrumental in its establishment. Until 1934 the PTR was part of the Reichsinnenministerium (the Reich's Ministry of Interior Affairs).