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Atomic time by mouse click

The PTB's new time service for the synchronization of computer clocks


[es] The Physikalisch-Technische Bundesanstalt (PTB) now sends its time signals also through the Internet. Via two time servers accessible to the general public (ptbtime1.ptb.de and ptbtime2.ptb.de), the signals coming from the Braunschweig atomic clock directly reach the web. Whoever has the software required to make use of the Network Time Protocol (NTP) – a list of suitable programs can be found at www.eecis.udel.edu/~ntp/software.html – can have the clock of his computer set to Universal Time Coordinated. Among those to which the new PTB time service is of interest are trade and industry and the banks: it allows easy access to the exact PTB time, for example, when precise time data are required for the control of production processes or for money transactions. More detailed information is available at the PTB's stand at the Hannover Fair (March 20 to 25).

Wherever several computers work together, for example in computer-controlled production plants or processes, the computer clocks must have been synchronized (set to the same time) so that no disturbances occur. Time also plays an important part in money transactions - to prevent that the same shares are suddenly held by two persons. The examples show that many institutions are interested to provide their computers with the exact time. This time can now be directly obtained from the national atomic clock in Braunschweig, where the time information is fed into two time servers via so-called time code generators.

The offer supplements the PTB's telephone time service which for some time now has provided computer clocks with the exact time via telephone modem and the public telephone network. "However, the new path is the most elegant method, in particular since the Internet connection is usually available anyhow", says Dr. Peter Hetzel, one of the persons responsible for the project. Some of the clients are even interested in using both possibilities offered - as a check.

And yet, not much can actually go wrong. The procedure is simple: load the software required for using the Network Time Protocol (NTP) from the web (www.eecis.udel.edu/~ntp/software.htlm), add the addresses of the two PTB time servers to the program (ptbtime1.ptb.de and ptbtime2.ptb.de) and the rest will take its course automatically. The only uncertainty factor is possible time delays on the path through the web, for which PTB cannot be held responsible. But Dr. Sibold, responsible for server operation, is convinced that "the resulting deviations will normally always be smaller than 1/10 of a second".

The Internet time service is the latest component of the PTB's comprehensive offer concerning time. The PTB's task (under the Time Act of 1978) to indicate and distribute the time governing "official and legal transactions" is fulfilled by it in different ways: by means of the time signals of the Braunschweig atomic clock, emitted by the DCF77 long-wave transmitter at Mainflingen near Frankfurt, the PTB controls radio clocks all over Europe - from the watch to the radio alarm clock to the station clock. In addition, it publishes the results of time comparisons between its atomic clocks and other time systems. One can learn, for example, how exactly the signals of the Global Positioning System (GPS) agree with the Universal Time Coordinated distributed by PTB. An offer which is intended only for professionals - in contrast to the new Internet time service. "We receive many enquiries from normal PC users who call the exact time from us once a day," says Hetzel.

Additional information:
At the Hannover Fair (March 20 to 25, 2000):
PTB stand (Hall 18, Stand B 020, telephone at Fair: +49 (0)511 89-438 04)

Dr. Andreas Bauch, telephone:+49 (0)531 592-4320, e-mail: andreas.bauch(at)ptb.de
"Unit of Time" section
Dr. Peter Hetzel, telephone:+49 (0)531 592-4330, e-mail: peter.hetzel(at)ptb.de
"Time and Frequency Distribution" section
Dr. Dieter Sibold, telephone: +49 (0)531 592-8410, e-mail: dieter.sibold(at)ptb.de
"Server Administration" section