Integrated Timing Systems

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Integrated Timing Systems Powered By Docstoc
					         Are Your Systems In Sync?
     How to Integrate Precision Timing Systems in
       Airports and Air Traffic Control Services
      By Angie Tiller, Marketing Co-ordinator, Time & Frequency Solutions

                                      TIME is an essential element in Airport
                                      Systems such as flight scheduling, baggage
                                      handling, FIDS & PIDS, CCTV, telephone
                                      systems, and so on, but particularly in
                                      mission critical applications such as Air
                                      Traffic Control. Time & Frequency Solutions
                                      have worked with the individual systems
                                      suppliers over the past thirty years to
                                      develop a centralised timing concept
                                      particularly suited to airports and ATC

                                       A Synchronised Approach
                                       During the planning stages of a project it is
all too easy to neglect the procurement of a centralised timing system that could
be integrated to all elements within a modern airport or ATC system.

In most cases the control and display of time is left to individual system suppliers.
Although each piece of equipment can be set to a standard reference and
modern computers are supplied with fairly accurate clocks, every system will
have its own tolerances and will drift at different rates.

Typically, individual departments often supply their own timing solutions leading
to a multitude of diverse ‘standards’. Although each standard can then be
synchronised to an agreed time reference this process must be repeated at
regular intervals to ensure that a constant time-of-day indication is maintained
throughout the entire system. When a large number of facilities and possible
‘standards’ exist within system, major synchronisation problems are likely.

Common Time Source for All Airport Systems
Modern processing and working techniques have also brought many clocks and
digital time displays directly to operators’ workstations. Although the displays are
normally synchronised with their associated system servers, the lack of common
time source results in minor discrepancies, which are immediately apparent to the

In addition to the obvious visual discrepancies many current processing
techniques rely on precise timing for both internal and external functions.
Attempts to correct time within these systems can lead to major problems as the
processing cannot tolerate an abrupt, significant change in time. This problem is
aggravated when different systems are integrated together and attempts to
change the time on one piece of equipment can lead to problems surfacing on
another part of the system.

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Central Master Clock
A desirable configuration for an efficient
airport and/or ATC system utilises a Central
Master Clock integrated to all major
systems and sub-systems. This ensures
that all systems are automatically
synchronised to a common source.

The master clock is driven from an accurate
input signal. The choice of available
sources covers GPS, VHF, HF, MF, LF or
locally available standards. In many cases
GPS is the preferred standard as it offers
superior accuracy coupled with proven, off-
the-shelf modules and small discreet antennas.

Ideally this type of configuration should be used at the project design phase but
there is no reason why existing systems cannot be retrospectively fitted to
emulate this design philosophy. Many equipment suppliers now offer external
clock interfaces on their processors or can offer the facility as an accessory. If
software is locally produced, off-the-shelf clock synchronisation modules can be
obtained for most types of operating systems.

To overcome any potential internal timing errors, 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.

                                          System Solutions
                                          Time & Frequency Solutions have now
                                          provided turnkey centralised timing
                                          systems to a number of Airports and
                                          Air Traffic Control networks worldwide.
                                          These include the UK’s National Air
                                          Traffic Services, Slovakian Air Traffic
Services, Hong Kong & Zhu Hai ATC centres plus centres in Finland, Ireland,
Brunei, Hungary, Kuwait and Saudi Arabia. They have also supplied precision
timing to passenger areas in airports in the UK (Heathrow, Gatwick, Stansted,
Prestwick, Newquay) and around the world; most recently the prestigious Etihad
Terminal in Dubai.

These systems all utilise the rack mounted M210 or M211 Modular Timing
Systems, which allow the selection of particular interface modules, and time
message formats depending upon the equipment to be installed. This solution
also allows enhanced features, such as dual redundancy and the use of high
precision oscillators either for improved performance or to facilitate frequency
outputs for the synchronisation of communication systems.

Time & Frequency Solutions have made it their business to understand the
individual requirements of the Air Traffic Control and Airport Passenger Terminal
industry and this enables them to provide accurate advice regarding your
particular ATC timing application.

Time & Frequency Solutions Ltd
25 Eastways, Witham, Essex CM8 3AL
Tel: +44 (0) 1376 514114 Fax: +44 (0) 1376 516116
E-mail: Web:

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