Clocks can be set up to run as “stand alone” units, or can be synchronised via a masterclock unit to ensure accuracy throughout. The masterclocks available for synchronisation in Paris are DCF and GPS.  

Radio Synchronisation

How radio time synchronisation works

The MSF and DCF carriers are interrupted every second to encode time and date information with a full time, date and status message being transmitted every minute. The length of the individual carrier breaks determine the value of the coded information and the time of transmission within each minute determines the identity of each bit.

In addition to basic time and date information a 'second level' data set is transmitted during the last few seconds of each minute to provide warning of impending seasonal time changes, summer/winter time status together with parity bits which are used as part of the validation process for each message. At the start of each minute a unique bit pattern is transmitted called the 'minute identifier'.
Due to the possibility of transient interference or reception conditions causing corruption of the transmitted code signal or a total signal loss, the clock or master clocks use the MSF or DCF transmission as an update reference comparison rather than a continuous source of time information.

MSF & DCF receivers

The 484 series of radio time synchronisation receivers enable the time synchronisation of clocks, calendar clocks, time zone clocks and master clocks to accurate DCF and MSF radio time code signals.

• MSF transmits on 60kHz from Rugby with signals traceable to an atomic clock at the National Physical Laboratory.
• DCF transmits on 77.5kHz from Mainflingen, near Frankfurt/Main in Germany with signals derived from the Physikalish-Technische Bundesanstalt, Lab. Zeitenheit.

In theory the signals are receivable at a range in excess of 1000km from the transmitter, subject to the effect of a wide range of variables such as time of day, atmospheric conditions and the degree of screening between the transmitter and receiver. In practice increasing levels of noise pollution, particularly from mobile radio systems, result in a reduction of reception reliability and we now recommend GPS time synchronisation for time and reliability critical applications.

484.02 (MSF) receivers

The 484.02 (MSF) receivers are high performance units with dual crystal filters and dual ferrite antennas to provide omni-directional capability. The units are housed in robust IP65 rated cases suitable for protected external mounting.

case size: 160 x 80 x 55mm - 6.3" x 3.1" x 2.2"

484.06 (MSF) receivers

The 484.06 (MSF) receivers are low cost units with unidirectional antenna, fitted with a rotating mounting bracket for alignment and intended for internal use. Please note that the 484.06 receivers may not be suitable for use in a building with a steel frame or cladding.

Case size: 90 x 60 x 24mm - 3.5" x 2.4" x 0.9"(excluding mounting bracket)

GPS Synchronisation

488BGPS GPS time synchronisation system

The 488BGPS GPS time synchronisation system is designed to provide an extremely accurate, yet simple to install and maintenance free, time reference for the 4850 system master clock and 4860 NTP master clock.

The 488BGPS package comprises an active antenna mounted on a stainless steel post mounting bracket, a receiver/decoder module housed in a rugged, IP65 rated, wall mounting aluminium enclosure, a 5m coax cable between the active antenna and the receiver/decoder module and a 25m, four core cable between the receiver/decoder module and the master clock.

What is GPS?

GPS is a system of satellites in six orbits; each orbital plane equally spaced about the equator and inclined at 55 degrees. The satellites transmit highly accurate, real time, worldwide navigation information at a frequency of 1575.42 MHz that anyone with a suitable GPS receiver can use to identify their position, together with a precise local time. The GPS system was developed by the US government initially for military use and is now available for unlimited commercial access.

How GPS time synchronisation works

GPS satellites travel in nearly circular orbits every 12 hours at an altitude of 20,200km (10,900 nautical miles). The exact position of each satellite can be determined at all times. Each satellite continuously transmits a unique code sequence, derived from atomic clocks, which is tracked by the GPS receiver.

The transmitted information includes current orbital data for each satellite. The GPS receiver is able to identify each satellite by its code and is able to calculate the satellite's exact position in space. The GPS receiver uses the calculated information to determine its distance from several satellites. The receiver then uses a process called triangulation to compute its own position together with a precise utc time.

Wharton Masterclock 4850

The 4850 master clock provides a precise GPS system synchronisation solution for computer network, CCTV, security, voice recording, industrial process control and CCC applications in addition to its use in digital clock systems to control 400A series digital clocks, calendar clocks and time zone clocks displaying time or time and date in up to 15 different global time zones.

The 4850 masterclock may be synchronised from GPS, MSF or DCF radio time signals and is designed for simple installation and 'setup and forget' operation.

Masterclocks can additionally be fitted with an IRIG interface card for synchronising with a voice recording system, and an I/O card if timestamps need to be time synchronised.

NTP Synchronisation

NTP versions operates as a time server on a TCP/IP network, serving NTP/SNTP time-packets directly to clients on the network. Network Time Protocol (NTP) v2, v3 and v4 clients are supported in the unicast mode of operation (RFC1305 & RFC1119). Simple Network Time Protocol (SNTP) v3 and v4 clients are supported in the unicast mode of operation (RFC2030 & RFC1769).