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Precision GPS/GNSS based NTP Network Time Servers


GPS / GNSS Time and Frequency Systems

An overview on the broad conceptual aspects of a typical timing system.  Almost every timing system is different, so it is important to consider and discuss the overall requirements well in advance of equipment acquisition.

Time and Frequency Systems

Time & Frequency Systems generally receive one more timing signals from a Trusted Time Source such as GPS. Other time sources could be terrestrial signals such as MSF (transmitted from Anthorn, England) and DCF (transmitted from Frankfurt, Germany), or even Time code signal inputs, e.g. RS232, RS422, IRIG, AFNOR and NASA timecodes, which may be distributed from another Master Clock elsewhere.

The timing signal is used to discipline the internal clock in the master timing system such that the oscillator becomes exactly synchronised to the Trusted Time Source.  This means that if the TTS is removed, the Master Clock will continue to keep accurate time based upon the characteristics of the oscillator.

The internal clock (frequency standard or oscillator ), provides stability to the overall system if the GPS signal (or other synchronisation source) is interrupted for any reason. Many grades of oscillator are available, according to the stability grade required.

In general and in order to overcome multiple time code format requirements, Modular Timing Systems are used in conjunction with a wide range of optional modules to interface with whatever systems the customer requires.

For high availability , safety or security critical applications, we recommend the use of dual redundant systems, whereby the core elements of the system are duplicated and able to take over at any time should one aspect of the system fail.  Occasionally, there maybe a requirement for triple redundancy for very high integrity systems.  

The time signal is then converted into outputs, which can be in many different formats, such as serial, parallel, NTP and industry-standard time codes such as IRIG, and AFNOR.

Many standard systems are unable to cope with a multi-vendor requirement, where many different output interfaces are required, which is especially evident with legacy systems.

Diagram: An example of how an airport timing system interfaces with different legacy systems.