One aspect of digital signage that is very rarely talked about is the need for synchronisation, especially amongst networked systems. If a network of signs, especially outdoor digital signage used to deploy time-critical information such as timetables, emergency warnings or other time crucial content, is not properly synchronised, delays of minutes, hours and even days, can occur between individual screens.

There is more to proper synchronisation than just ensuring that the media delivery systems are set to the same time, as different system clocks in media players and computers, can, and often do drift at different rates. This means that in the space of a week, screens could be as much as a minute apart and the problem will exacerbate over longer periods.

Upload time-critical content on one machine, and the information could be obsolete by the time it is displayed on all the screens on a network.

Many emergency electronic signs along highways and motorways are accurately synchronised for this very reason to ensure all information appears at the same time – but how is this achieved?

Commonly, the time protocol NTP (Network Time Protocol), is used in computer networks and is often deployed in synchronised sign networks. It works by using a master time that it then distributes amongst all devices along a network, but problems can arise, especially when selecting a master clock.

It is very common for NTP users to use a source of Internet time as a master time source. And while these sources of time are claimed to be UTC (Coordinated Universal Time), an atomic clock source, it seems a good idea; however, online sources can be unreliable, the servers can go down and can lead a network to become out of sync remarkably quickly.

A solution is to use your own NTP time server; relatively inexpensive time server devices use a source of GPS or radio signals as the time source. These are far more reliable and ensure that an accurate, and secure source of time is always available.

NTP time servers are deployed by many computer networks, including motorway signage and other digital signage networks where time crucial information is a necessity.