The meaning of ‘right time’ varies with geographic position and with season of the year. The globe is divided into time zones and in many places the time scale is adjusted to summer and winter time. The ‘right time’ for a specific geographic position is called Local Time. However there is a universal time scale to which local time are related –the UTC (Coordinated Universal Time). The UTC scale is important to all general purpose time equipment. The UTC time zone is GMT (Greenwich Meridian Time).

To keep track of ‘the right time’ whatever time zone position actual, we need to measure time. In modern time technology two concepts are used to measure time; quartz crystal oscillators and radio signal synchronization and usually in combination.

A time base - which can be a stand alone clock, a master clock or timecentral - can measure time from a built in quartz crystal oscillator. The quartz crystal as such has no information on time but it provides a reliable frequency source in form of electrical potential which can be used to measure time with high accuracy. Quartz crystals are used in clocks because they are stable to variations in temperature and provide stabile impulses.

A time base can also be synchronized by radio signals. The general principle is that time signals for radio synchronization are sent every minute when the second scale is 00. The receiving unit controls and compares the time message with its internal time. If there is a difference it automatically corrects in accordance with the received time. If time messages are unclear or missing the unit continue to measure time with its built in quartz crystal. This concept means that it is sufficient to receive clear signals only a few times during a day to still keep high accuracy in time measuring. Various signal systems for the synchronization of time are available. Some of the most common systems are described below.

GPS is a world-wide satellite system that operates a time scale and transmits information for synchronizing to UTS with extreme high accuracy.

DCF 77 signals transmitted from Germany is the most frequently used signal in Europe. The signal is sent every minute and comprise minute, hour, year and date.

In France the national TDF transmits signals for time synchronization and in Great Britain the MSF-Rugby sends similar signals for synchronization. RDS is a signal transmitted over the FM band in Scandinavia.

Many other European countries have national signal system which includes time data and which can be used for time synchronization.