Physikalisch-Technische Bundesanstalt (PTB)

 Physikalisch-Technische Bundesanstalt (PTB) is the German National Metrology Institute (PTB) - a higher federal authority and research institute for science and technology based in Braunschweig and Berlin. The Institute is responsible for the definition, retention, and adoption of international units of measurements and for supplying national standards. This includes providing the exact time using atomic clocks, which is then transmitted via internet and radio wave transmitters.