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AFNOR |
A timecode developed by Association Francaise de Normalisation. |
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Atomic clock |
A clock using the natural resonance frequency of atoms as a time counter source. Caesium is the most accurate (and very expensive); rubidium is next accurate and is less cost-prohibitive and so is more widely used in commercial applications. |
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Board- Level /
Bus-Level Timing |
Refers to timing boards used with computers to provide accurate local time information. Various categories available including PC, PCI, VME/VXE |
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Caesium, cesium |
Element used in highly accurate atomic clocks |
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COTS |
Commercial Off-the-Shelf. |
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DCF, DCF-77 |
Low frequency terrestrial radio signal from Frankfurt, Germany |
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Disciplined
oscillator |
An oscillator that has been 'disciplined' or pre-calibrated to a time signal, e.g GPS |
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Frequency
Standard |
Stable oscillator frequency used for calibration or reference |
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GALILEO |
European Satellite Navigation System. It is currently in the process of being developed by the European Space Agency, and is intended to be fully operational by 2008. |
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GLONASS |
Global Satellite Navigation System launched by the Russian Federation in 1999. |
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GMT |
Greenwich Mean Time, local legal time in Britain |
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GPS |
Global Positioning System |
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HaveQuick |
Type of timecode that enables synchronous frequency hopping. It matches a Word of the Day code with Time of the Day code and a net number code, which is the table of frequencies to be used for that transmission. |
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IRIG |
Inter Range Instrumentation Group. Developers of a set of timecodes which are widely used. |
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LCD |
Liquid Crystal Display; Liquid crystals are suspended in small amount of liquid and then sandwiched between two glass plates. When an electrical current is passed though, the crystals align so that light cannot pass through them. |
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LED |
Light Emitting Diode; A display technology that uses a semiconductor diode that emits light when charged. |
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Master clock, masterclock |
A clock used as a primary reference for other sub-master (slave) clocks |
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MSF, MSF-60 |
Low frequency terrestrial radio signal from Anthorn, Cumbria, England, broadcasting the national time standard |
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Nanosecond |
One billionth of a second (10-9) |
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NIST |
National Institute of Standards and Technology, the National Measurement Institute in the United States |
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NPL |
National Physical Laboratory - the UK's national measurement laboratory |
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NTP |
Network Time Protocol, a method of transmitting time data across a computer network in order to synchronise internal clocks to a common time source. |
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Oscillator |
An electronic device which generates a recurring waveform (the resonance frequency). This frequency is a counter to measure time and so is used extensively in clocks as a frequency reference source. |
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Picosecond |
One trillionth of a second (10-12) |
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PRC |
Primary Reference Clock |
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SDH |
Synchronous Digital Hierarchy - the standard for transmitting digital information over optical networks such as SONET. |
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SMPTE |
Time code developed by the Society for Motion Picture and Television Engineers. Adds a unique number onto each frame on a videotape denoting hours, minutes, seconds & frames in order to assist logging and editing of film, video and audio recordings. |
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SNMP |
Simple Network Management Protocol, the internet protocol for network management software systems |
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SONET |
Synchronus Optical Network |
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Stratum 1 Timeserver |
Device with a direct connection (not via a network) to a Stratum 0 time reference source |
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TAI |
International Atomic Time. Time standard based on the vibrations of caesium atom. |
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Time server |
Device that distributes time over a computer network in order to synchronise all the internal computer clocks. |
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Timecode |
Time information in a coded signal format which facilitates synchronisation of any combination of message output, e.g. pictures with sound. |
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USNO |
United States Naval Observatory, home to the atomic clock which is the source of national time in America |
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UT1 |
Time as defined by the Earth's rotation |
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UTC |
Co-ordinated Universal Time. The time calculated as a weighted average of about 200 atomic clocks around the world. |
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