Frequently Asked Questions:

-   Clock Displays
-   Which model of display best suits my requirements?

Our displays are optimised for different applications.

The NTDS and TCDS displays are easy to read, have controllable light levels, are ideal for all indoor applications, eg. control rooms, studios, factories, conference rooms, offices, trading floors, hospital wards, etc.. With their optional stainless steel housing and / or special protective lenses these same displays can also be used in a variety of semi hazardous areas, eg. wipe down clean rooms, operating theatres, industrial kitchens, etc.

The ECO displays are fully waterproof and designed for outdoor or indoor use. They also offer high illumination levels allowing them to be read in sunlight, and some of the range have water tight connectors to enhance the external protection rating to IP65.

-   Which LED Colour is best?

All colours work well. The colour that will best suit your needs depends on where you plan to locate the display; in general:-

In semi dark areas like studios and control rooms red, green or amber are easy to read and kind on the eye.

In modern looking conference rooms some clients like our White and Blue colours which create a modern feel or they simply match corporate house colours, etc.

Blue and white tend to be the brighter colours so if an operator is required to look in the direction of the display for long periods of time they may prefer red, green or amber.

-   How far away can I read the Time?

Viewing distances vary according to site conditions, eye sight, the LED colour and display type. Red LEDs are generally considered the easiest to read. Green and Amber LEDs are easy on the eye in dim lighting, while Blue LEDs tend to be the hardest to read from afar. The 7 segment “diffused LED technology” used in our NTDS and TCDS displays make them easier to read at a distant over an equivalent size dot matrix display like our ECO ones. Depending on the displays location they may suffer from reflections and / or glare, which will reduce viewing distances. We can offer special lens coatings to reduce glare. Any airborne “smog” will also reduce the viewing distances. Also consider how quickly the viewer must read the display – most people can read over longer distances if they take some time to focus and / or squint their eyesight; In many work situations such time may not be available. The difference between a quick glance distance and the long stare distance can be around 50%.

As a general safe guide for quick glancing assume that for every 3m the viewer is away from the display the character heights should be 1cm - and round up to the display height that is bigger. So for the TCDS and NTDS displays our suggested easy reading (and the stare or max limit) distances for each display size are:-

Display Hieght Glance Distance Stare Distance
1.5cm (0.6 inch) 4.5m 9m
2.5cm (1 inch) 7.5m 15m
5.8cm (2.3 inch) 15m 30m
10cm (4 inch) 30m 60m
18cm (7 inch) 50m 100m
-   Should I use PoE?

Power Over Ethernet (PoE) is an option available on most of our NTDS and ECO displays, and conforms to the IEEE 802.3af standard. PoE sends 48VDC power along the network cable - in audio and RF terms it is the equivalent of phantom powering. PoE eliminates the need to run a mains power cable to your display.

Check if your network router offers any PoE ports, how many and if there are any power limitations. Some makes of router quote PoE as x ports with a max total of y watts, so you may need to do some quick calculations. Check our data sheets for the precise load required by each display but in general our displays consume less than 15w which is the PoE standard class 0 device limit. If you have any doubt or are unsure how to do the calculations please contact us if you need help.

Bear in mind that long network cable runs will drop power (and volts): So always use a good quality Cat 5 or 6 copper cable and RJ45 connectors and also check any patch leads / junctions boxes. As a basic guide a good cable should be able to power the display over a 100m cable run. If you have some very long cable runs and / or do not have enough PoE router ports than consider our PSPoE15 in line power supply. Simply plug this inline PSU into the mains at some convenient location and run a network cable from the router into it and another out of it to the display. If you only require a few displays with PoE these in line power supplies may work out less expensive and disruptive than buying a new PoE router.

-   How do I control my display?

The NTDS and TCDS displays come with our free WinDiscovery App which runs on Microsoft Window devices. It will allow you to set up the display brightness, and other configuration / running parameters easily - with little or no knowledge. You can also use it to monitor what the display is showing. With the NTDS displays this software can find the display over a LAN and will control multiple displays, making life very easy. As the TCDS display uses timecode as a reference rather than a network feed the computer is plugged into the display using a USB port. For MAC and Linux users the displays can be set up using Telnet.

The ECO displays have a built in web server utility, connect to it with your browser to make all the set up adjustments needed.

-   I have multiple timecode displays, how should I wire them?

Time code is a digital signal that can travel along either co-axial cable or balanced twisted pair (audio) cables. It typically goes from a low impedance output to a high impedance input, and as such you can connect several displays to the same timecode output. However this is not considered good practice, since a fault on any one wire or device could stop all the other displays working. Very long cable runs may also lead to signal reflections and attenuation issues and may upset one or more display – sometimes giving an intermittent problem which may be hard to find. Therefore it is good practice to use time code distribution amplifiers - like the TCA100 – which isolate the masterclock and the various clock displays.

-   Master clocks

-   How do I synchronise my server to a world reference time?

This is where the GNSS (GPS/GLONASS) option comes in – although there are other ways! Basically you need to see one of the world traceable time references, such as those kept by NPL in the UK and NIST in the USA. These organisations make their time available in a variety of formats. The simplest (but least accurate) is to use a NTP Internet server, so you could just point your master clock to the correct server domain (web) address and open port 123 in your firewall. The reason this is not very accurate is that to have an accurate time you need to know how long it takes each time stamp to travel over the web and arrive in your server. Unfortunately there is no easy way to do this and it can change with every packet.

A better way is to use their off-air signals. A few decades ago this would have been a long wave radio signal but now these have been replaced by numerous satellite clusters, the best know being the USA GPS system. These satellites transmit a highly accurate time and traceable time signal, which our masterclocks can receive and use to synchronise (discipline) the time oscillator.

-   Why do I need a master clock at all if GPS is so accurate?

This is a good question an accountant might ask! Basically there are many reasons. Firstly the GPS are extremely low level signals and may disappear for long periods –fog, snow, heavy rain, cloud cover can all block the signal from reaching your antenna. Then there are risks from other RF devices interfering and blocking the signal – someone’s mobile phone near the antenna might be all it takes. Then over the years large objects like buildings can appear and block the signal. And we haven’t even mentioned someone damaging the RF cable, knocking the antenna, etc. etc.. To ensure you have continuous accurate time (all the time) your master clock system should have a very stable “fly wheeling” oscillator in it. This will allow it to handle the periods when access to the GPS reference is interrupted.

Such an oscillator has inertia which can override any sudden or odd changes in the GPS time (perhaps caused by someone trying to interfere with the RF signal – a so called spoof attack), enabling your system to maintain a consistent and accurate time.

Our masterclock systems can monitor multiple satellite constellations (eg GPS and GLONASS) and automatically take the strongest, most accurate, time references, thereby improving both reliability and accuracy.

As well as keeping accurate time a masterclock outputs multiple time signals and is able to drive large numbers of slave devices – such as clock displays or network computers. Being a dedicated piece of hardware it will not suffer from outages, re-boots or other interruptions that a software based solution will. It also makes your life easier as it becomes the single entry point in your system, so ongoing network security and world time traceability issues are far easier to manage.

-   Why do I have a choice of 3 oscillators (and which do I choose)?

‘Time is relative’ a famous scientist once said! Your network may require time accuracy in the order of tens of nanoseconds, a few microseconds or you may just simply be looking to display the correct time of day on multiple clock displays (in which case tens of milliseconds accuracy will suffice). We offer a choice of three high quality high stability oscillators to best match your budget and level of accuracy required.

You may wish to run your master clock independently or you may synchronise it to one of the worldwide time standards (like GPS). Such time standards typically only send out time stamps every few seconds - so your master clock needs to free run between such updates. If you are aiming to achieve accuracies to nanoseconds then 1 or 2 seconds is a very long time! Also and more commonly for most users, there will be times when your master clock loses connection with the world time standard, and will go into what is known as holdover mode (ie free running). Such outages may last a few hours or even for many days. For example GPS outages occur quite routinely due to atmospheric conditions. In addition service interruptions, knocked antennas or damaged equipment, can lead to outages lasting days or weeks. During such outages your masterclock can be set to switch to a fall back reference (if one is available) or it will go into holdover mode. In either event if the output time is not to jump a stable oscillator is required to ensure a steady continuous time signal.

Thus if you are synchronising to a worldwide time reference than the high stability oscillator is mainly a stop gap measure, and not every user will need our Rubidium (sometimes known as atomic clock) option. As a general rule, the more precision (ie nano, micro, or millisecond) needed the better quality High Stability Oscillator should be used to maintain stable time accuracy. Also bear in mind that instability (ie jitter, a bit like electrical signal noise), accumulates! The clients that your masterclock serves will always be slightly less accurate than your masterclock! Therefore having the highest stability in the masterclock is essential!

For some applications it is possible to calculate the level of stability required for a given level of accuracy over a given outage time. Contact us if you need any further help or information.

-   How do I control my server from a Windows Computer?

There are three ways to set up and monitor your Masterclock server from a Windows 8+ platform. The WinDiscovery app we provide is perhaps the easiest to use. WinDiscovery will automatically search and find all the masterclock devices on your LAN (masterclocks and clock displays). You then click on the device you want to control and a window opens for that device. The GUI is intuitive, quick and easy to use.

Window users can also use both the Telnet or SSH interfaces – although you may need to download suitable terminal emulation software on newer versions of Windows.

-   How do I control my server from a Linux Computer?

Telnet and SSH (Secure Shell) are the two ways to control our Masterclocks from a Linux or UNIX computer. Telnet is a well proven, text terminal method which offers easy connection, and is secure when connecting directly. SSH offers the same level of control as Telnet, has similar menus and offers high levels of security as its messages use encryption. SSH is the better choice if you wish to control the masterclock over a network. Both methods are quick and easy to use, and both offer the same full set of control and monitoring parameters, and have on line help to assist you. With SSH you can disable Telnet access, create your own user account(s) / passwords to better secure your Masterclock.

-   How do I control my Masterclock from an Apple (MAC) Computer?

Telnet and SSH (Secure Shell) are the two ways to control the Masterclock from your Macintosh operating system. Both are text terminal emulation methods, of which Telenet offers easy connection direct from your computer. SSH transmits encrypted messages over the network and so is the preferred way to control the Masterclock on larger networks. SSH allows you to create user accounts / passwords and disable Telnet to further secure your Masterclock. SH and Telnet are both text based control methods, which are quick and easy to use, and both offer the same full set of set up and status parameters, with on line help to assist you.

-   Time formats?
-   What is NTP?

Network Time Protocol is one of our oldest computer protocols. Updated over the decades to offer better accuracy, stability and security, it is currently on version 4 (RFC-5905). It is maintained as a public protocol (IEN) so can be viewed without charge –www.ntp.org. A cut down version known as SNTP was developed for simpler network situations. NTP is currently the default time keeping protocol in all the world’s major operating systems, and so is likely to remain the major network timing protocol of choice for many years to come.

NTP clients need to be manually adjusted to allow for network latency if accurate synchronisation with a world time reference is to be achieved. As latency over the world wide web is practically impossible to measure, an easier way to get an accurate LAN time reference is to use a local NTP master clock that receives a traceable reference from a satellite cluster. Along with more accurate local network time using GPS/GNSS satellites also allows vulnerable firewall ports (especially port 123 -which NTP normally uses) to be closed, thus enhancing network security. For home uses where security and sub second accuracy is not such a high priority it is perfectly possible to use one of the national NTP world master clock / servers as a time reference.

With a correctly configured NTP masterclock, network time accuracy to traceable time of just a few tens of micro seconds should be achievable (and tens of nanoseconds is theoretically possible). The protocol has various software techniques to measure the network latency, but these mostly assume server / client to and back latency times are the same. Some of these tools need to be manually used. Changes in the network can change its latency, requiring the calculations to be run again. PTP beats NTP in this aspect – see next answer.

-   What is PTP?

Precision Time Protocol is a recent protocol managed by the IEEE as IEEE1588. PTP can be used over most types of network (not just TCP/IP) including many industrial networks – like CanBus. PTP has the ability to measure network latency time, and automatically correct client time. It can achieve synchronisation accuracy to sub micro seconds, with the correct hardware. PTP allows clients to automatically choose the best master available – (in PTP lingo these are called Grand Masters!). For networks that do not use the latest PTP enabled hardware there are “backward” compatible modes although many of the advantages over NTP are then lost. PTP and NTP can co-exist on the same network. In 2004 the IEEE revisited the PTP specification and issued a newer version known as IEEE1588v2 which is the current definition.

PTP enabled (network) hardware can time the PTP packets in and out, and modify the PTP packet delay information. Thus the PTP packets store the total network delay (ie latency) when travelling through the network. PTP enabled hardware has a premium price and not every installation can justify its use. The IEEE created a concept of “profiles”, which allow each industry to decide the level of investment and accuracy it considers good practice. Profiles are essentially a best working practice document for that industry and give ‘advice’ on how to implement PTP over a network, set up the various PTP ‘switches’ in order to meet that industry’s deemed accuracy requirements. Our GMR grandmaster clocks come with a predefined standard profile and allow users to change the settings in order to meet specific profile required settings.

-   What is Timecode?

Timecode is a digital signal (in basically the audio frequency range) that travels over twisted pair wires (balanced format) or co-axil cable (unbalanced). There are several different standards of timecode, developed over the years by specific industry bodies. They are broadly all similar in concept yet incompatible in format! The major ones are:-

SMPTE / EBU. This standard was developed by the film and television industry, basically to synchronise sound tracks to the film / video pictures. As such it conveys hours, minutes, seconds and either 24 or 25 or 30 frames per second. It can also carry the date (or other basic user) information. It is widely used in TV studios to synchronise video recorders and clock displays together.

IRIG (Inter-Range Instrumentation Group) was a USA military time standard that has been adopted by many research institutions as an accurate way to transfer time information between different equipment. There are several different versions, denoted by various letters after IRIG the most common versions being IRIG-A, IRIG-B and IRIG-E. Some of the different versions relate to electrical connectivity but others relate to data rates and / or time stamp periods. Most of them carry hours, minutes and second information, some versions also carry sub seconds and others have date information.

Needless to say IRIG timecode is not compatible with EBU/SMPTE - although our Masterclocks will work with SMPTE/EBU and the IRIG-A, -B and -E versions.

-   What is Pulse per second?

Pulse per second (PPS) is one of the oldest time keeping formats, having survived the test of time. In addition to synchronising legacy clock displays, it is still used for very accurate time synchronisation - usually for internal equipment applications. It is a 5 Volt peak to peak TTL type of square wave pulse, which has one rise and one fall every second. By convention the rising edge is used for the accurate timing reference, and time accuracies to the order of a few tens of nanoseconds can be achieved.

-   Can I convert from Timecode to NTP / PTP? (or Visa Versa?)

Yes many of our products will allow you to do such conversion. Please Contact us for more information and advice.

-   Why no prices on your web site?

There are several thousand different build configurations across the range of products. Many of these products are assembled to order and may have conflicting options. To help you we manually check your configuration before any quote is raised.

Do use this Contact us link to tell us what it is you would like a quote for.

-   I cannot find the answer to my question.

We are sorry to hear this. If you have a product related question please use this contact us link to send your question and we will try and answer it quickly.

Top of page