Time synchronisation

In an interconnected world, time synchronisation is of paramount importance. Whether for computer servers, telecommunication networks, or critical infrastructures, it is fundamental to ensure that the time displayed on each device is identical and reliable.

Master clocks and Time servers distribute the time to clocks and other systems. There are different means of synchronisation available. The two main transmission modes are the AFNOR coded time and the NTP.

Types of time synchronisation

Synchronisation via NTP network (Network Time Protocol)

The NTP is one of the most widely used methods nowadays for synchronising computer clocks across local networks. It achieves highly accurate synchronisation by using a time server as reference.

Advantages :

Easy integration in IP networks
Scalable and reliable
Accuracy generally in the millisecond range

The Network Time Protocol RFC 5905 transmitted over TCP/IP networks calculates and corrects the drift in the propagation time of this information on local or remote networks (wired Ethernet or wireless Wi-Fi networks).

This solution uses communication networks to transmit an NTP time protocol (Network Time Protocol) meeting the RFC 5905 standard in unicast, multicast or broadcast mode via a TCP/IP network. It is particularly economical to install and wire, and uses the existing IT network in buildings. It allows for synchronisation of NTP clocks but also of all connected computer peripherals without requiring interface units.

The time server allows for time setting of computer networks from one or several remote buildings.

Slave clocks can be powered by two types of power supply: 230 VAC or PoE*
Connection of NTP clocks: On an RJ45 socket or via Wi-Fi

*In PoE version, clocks are powered by an identical RJ45 connection.

Configuration of NTP slave clocks
During installation, clocks are being configured remotely by set of clocks or according to the models selected: IP address of the NTP server and clocks (DHCP or fixed IP), choice of time zone, automatic summer/winter time change.

The NTP time synchronisation is the most widely used in new buildings nowadays, since the IP infrastructure is already in place.

Synchronisation via PTP (Precision Time Protocol)

The PTP (IEEE 1588) has been designed for applications requiring more accurate synchronisation than NTP, especially in industrial environments and telecommunication systems. It enables to synchronise clocks with an accuracy down to nanoseconds, which is essential in systems requiring a high degree of accuracy.

Advantages:

Greater accuracy than NTP
Suitable for local networks (LAN) where latency is low
Used in specific sectors such as broadcast, telecommunications and industrial automation

AFNOR NFS 87500 coded-time transmission

This is a standardised code in time message and in frequency. It is amplitude modulated and can distribute the time to more than 200 clocks up to 20km over a single telephone line. It has the advantage of not interfering with surrounding lines and of being relatively undisturbed by industrial interference.

Transmission of the time message on a telephone pair
Unidirectional time message
Maximum number of clocks. : 200
Distance up to 20km : link between clocks 1 telephone pair
Clock power supply: 230VAC or 24 VDC

Time synchronisation sources

GPS synchronisation (Global Positioning System)

The GPS is one of the most accurate time sources available. GPS receivers picking up satellite signals can synchronise devices with a level of accuracy down to nanoseconds. This solution is widely used in telecommunication systems, banking networks, and scientific applications.

Advantages:

Extreme level of accuracy
Independent from the local network
Used for applications requiring global synchronisation

GNSS synchronisation (Global Navigation Satellite System)

The GNSS synchronisation refers to the use of Global Navigation Satellite Systems (GNSS) to obtain an accurate and consistent time reference. These systems, such as GPS (United States), Galileo (European Union), GLONASS (Russia) and BeiDou (China), provide an extremely accurate time.

GNSS synchronisation is based on the transmission of radio signals by satellites, containing information on the exact time at which the signals have been transmitted and the position of the satellites at that time. When a GNSS receiver picks up these signals, it uses this information to calculate is own time and position.

Advantages:

Maximum accuracy
Overall accessibility
Used in different sectors: telecoms, energy, finance, transportation
High reliability

Radio frequencies

The DCF77 or ALS162 system uses time signals from a reliable external source, based on antennas respectively set up in Germany and France. These synchronisation sources enable to maintain accurate synchronisation in a network.

Time codes

AFNOR NFS 87500, ASCII 485, NMEA 0183

Advantages:

Originated from a known source via a cable link
Good immunity to industrial interference (Afnor NFS 87500)

NTP time protocol

Advantages:

UTC time
Standardised protocols
Bidirectional message which allows for monitoring and traceability
Connection to an RJ45 socket

Gorgy Time expertise

Gorgy Time is a French SME, technological leader recognised in the field of time synchronisation. For over 50 years, it has been designing, manufacturing and selling clocks, modular time centres and time servers.

Since its creation, Gorgy Time has been technologically ahead of its time. It is at the forefront of performance, and eco-responsibility.

Anticipation of needs

Our profession has always been following and often anticipating the evolutions in transmission modes (impulse, coded time, PPS, NTP, PTP,...) as well as in external synchronisation sources (radio transmitters, GPS, GNSS,...).

Besides, in order for our clocks to operate in an highly accurate and reliable way in the event of disruption, we have developed quartz time bases, with increasing accuracy.

In 50 years, Gorgy Time as strong advocate for standardised and secure synchronisation, has been able to develop quartz time bases meeting the requirements of global market.

Synchronisation via a reference time base	1974	Impulse time distribution: a master clock sends a 1-second polarised impulse every minute on a telephone pair. This technology has been created in 1920 and is always used for small installations.
Synchronisation via a reference time base	1987	The standardised coded time distribution (AFNOR NFS 87500 code) has been developed in 1987 at the instigation of Gorgy Timing. This is the most widely used wired transmission mode worldwide.
Network synchronisation	2001	Time synchronisation over ETHERNET and WIFI networks: by using the NTP protocol, a LEDI NETWORK time server or an RT 4000 time centre distributes the time information on the ETHERNET network. The clocks receive this time information continuously and they all display the same time, as does the whole computer system of the company.