This resulted in the common terminology "the MSF signal", which is still used by the NPL.The official history of the service says that "Rugby was given an additional commitment for the transmission of reference Modulated Standard Frequencies", but no actual explanation is given for the call sign "MSF".
It was funded by the former Department for Business, Innovation and Skills; The signal, also known as the MSF signal (and formerly the Rugby clock), is broadcast at a highly accurate frequency of 60 k Hz and can be received throughout the UK, and in much of northern and western Europe.
It consisted of 306 pulses in the five minutes up to and including and GMT, with a longer pulse at the start of each minute.
Frequency-shift keying was added in 1967, making the signal harder to use as a frequency reference.
The 60 k Hz signal finally became an uninterrupted 24-hour service in 1966, and the frequency references were discontinued in February 1988.
The change in location and consequent change in signal strength can make some equipment designed to use the MSF signal fail to continue doing so.
The second marker is transmitted with an accuracy better than ±1 ms relative to Coordinated Universal Time (UTC), which is itself always within ±0.9 seconds of Universal Time (UT1) which is the mean solar time which would actually be observed at 0° longitude.