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.
The PTB is entrusted by the Time Act to realise and disseminate legal time to the public. The most popular means is the transmission of standard frequency and time signals by the longwave time signal DCF77. It is responsible for four German caesium atomic clocks, CS1, CS2, CSF1 and CSF2 . These atomic clocks have an important role in maintaining accurate worldwide time of day as they provide the German UTC(PTB) legal time standard which - combined with other official atomic time standards - is used by the Bureau International des Poids et Mesures to create a single, official Coordinated Universal Time (UTC). In addition, the PTB operates the "stratum 1" ptbtime1.ptb.de, ptbtime2.ptb.de and ptbtime3.ptb.de public Network Time Protocol 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, and electroshock weapons.