Brief chronology of the atomic clock era at PTB
Jan. 1, 1959
Official start of the emission of standard frequency and time signals via the transmitter DCF77 of the Deutsche Bundespost near Frankfurt.
Signal generation based on highly precise quartz clocks, steered according to astronomical observations.
Late 60ies quartz clocks steered towards atomic clocks operated in Braunschweig.
On June 5, 1973, introduction of a time code for the signals emitted (still valid today).
1961
Application for the construction of an "atomic clock house" at PTB.
1963
Start of construction work.
March 1967
Move of the PTB "Laboratory for the Unit of Time" to the new Atomic Clock House.
October 1967
International redefinition of the second by the 13th General Conference for Weights and Measures.
Definition of the atomic second: "The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom."
1969
The atomic clock CS1 (caesium-one) becomes operational.
1978
With the Time Act of July 25, 1978, PTB becomes responsible for legal time.
1980
First introduction of Daylight Saving Time after World War II.
1985
The atomic clock CS2 becomes operational. From 1991 onward, it furnishes the seconds of legal time.
1988-1992
Two more atomic clocks (CS3 and CS4) become operational.
1999
With CSF1, an atomic clock of the most recent generation (caesium fountain clock) starts ticking at the PTB. It is immediately by far the best clock in Germany, initially with a rate uncertainty of one second in thirty million years
June 2005
The CS4 atomic clock (the "twin sister" quasi of the CS3, which is still "ticking") is being sorted out and is moving on to the Braunschweigisches Landesmuseum at the Burgplatz. There it will be placed in the midst of an exhibition on the subject of "time" (open daily, except Mondays, admission free.)
Today
All these atomic clocks except CS4 are still operating. They contribute substantially to the making of International Atomic Time.