How Time & Frequency Systems work
Since not everyone is technical, we thought we’d explain how time & frequency systems work. The Time & Frequency System receives a signal 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 timecode signal inputs, e.g. RS232, RS422, IRIG, AFNOR and NASA timecodes.
The signal then disciplines the internal clock in the master timing system. 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.
Diagram: example of how an airport timing system interfaces with different legacy 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.
This requirement is especially evident with legacy systems. We have overcome this by producing our M211 and M210 Modular Timing Systems together with a wide range of output modules to interface with whatever systems the customer requires.
Time & Frequency Solutions recommend the use of a ‘dual-redundant system’ whereby a changeover unit links two timing systems with the ability to switch the signal from one to the other if a failure occurs. Sometimes a triple-redundant system is more appropriate, linking three timing systems.