View source for Time from NPL (MSF)

{{Short description|Time signal transmitted from Anthorn Radio Station near Anthorn, Cumbria}}
{{Location map|Cumbria
|label      =
|lat        = 54.91
|long       = -3.28
|caption    = <small>Map showing the location of the Anthorn VLF transmitter in Cumbria.</small>
|float      = right
|background = white
|width      = 200
}}
The '''Time from NPL''' is a radio signal broadcast from the [[Anthorn Radio Station]] near [[Anthorn]], [[Cumbria]], which serves as the United Kingdom's national time reference.<ref name="nplmsf">{{cite web|title=NPL Time Metrology|publisher=National Physical Laboratory, UK|url=http://www.npl.co.uk/science-technology/time-frequency/products-and-services/time/msf-radio-time-signal|access-date=8 February 2012|archive-date=27 June 2013|archive-url=https://web.archive.org/web/20130627102609/http://www.npl.co.uk/science-technology/time-frequency/products-and-services/time/msf-radio-time-signal|url-status=live}}</ref> The time signal is derived from three [[atomic clock]]s installed at the transmitter site, and is based on [[time standard]]s maintained by the UK's [[National Physical Laboratory, UK|National Physical Laboratory]] (NPL) in [[Teddington]].<ref name="leaflet">{{cite web|title=MSF The Time from NPL |publisher=National Physical Laboratory, UK |access-date=6 April 2007 |url=http://www.clockco.co.uk/documents/msf.pdf |url-status=unfit |archive-url=https://web.archive.org/web/20071031013926/http://www.clockco.co.uk/documents/msf.pdf |archive-date=October 31, 2007 }}</ref> The service is provided by [[Babcock International Group|Babcock International]] (which acquired former providers [[VT Communications]]), under contract to the NPL. It was funded by the former [[Department for Business, Innovation and Skills]];<ref name="nplmsf" /><ref name="TROGER">{{cite journal
|title = MSF and the NPL
|journal = Radio User
|issn = 1748-8117
|date=July 2014
|first = Roger |last = Thomas
|publisher = PW Publishing Ltd
|location = Bournemouth UK
|pages = 47–49
}}</ref> {{As of|2017|lc=y}} NPL Management Limited (NPLML) was owned by the [[Department for Business, Energy and Industrial Strategy]] (BEIS), and NPL operated as a public corporation.<ref>{{cite web|url=http://www.npl.co.uk/about/what-is-npl/|title=What is NPL?|website=National Physical Laboratory|access-date=9 October 2017|archive-date=26 June 2015|archive-url=https://web.archive.org/web/20150626233142/http://www.npl.co.uk/about/what-is-npl/|url-status=live}}</ref>
The signal, also known as the '''MSF signal''' (and formerly the '''Rugby clock'''), is broadcast at a highly accurate frequency of 60&nbsp;kHz and can be received throughout the UK, and in much of northern and western Europe.
The signal's [[carrier frequency]] is maintained at 60&nbsp;kHz to within 2 parts in 10<sup>12</sup>, controlled by [[Atomic clock|caesium atomic clocks]] at the radio station.<ref name="nplmsf" />
== History ==
[[File:Rugby Anthorn MSF.jpg|thumb|Received, at Lesvos Island, during the transfer from Rugby to Anthorn]]
A radio station at Rugby was first operated by the [[General Post Office|Post Office]] from 1926, with the call-sign GBR. From 19 December 1927, it broadcast a 15.8&nbsp;kHz time signal from the [[Royal Observatory, Greenwich|Royal Observatory]] which could be received worldwide. It consisted of 306 pulses in the five minutes up to and including 10:00 and 18:00 [[Greenwich Mean Time|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 time signals, preceded by the callsign "GBR GBR TIME" in [[Morse code]], were transmitted during the 5 minutes preceding 03:00, 09:00, 15:00 and 21:00. Transmitter GBZ on 19.6&nbsp;kHz was used as a reserve, when GBR was off-air for maintenance.<ref>{{cite book | author=Gerd Klawitter | title=List of Time Signal Stations | year=1980 | pages=30–31 | edition=9th }}</ref> Eventually, time signals from GBR were terminated in November 1986 and it is no longer used as a frequency reference.<ref name="faqs" />
The MSF signals started in 1950, following the transmission pattern [[#Protocol|described below]]. They were originally intended to provide frequency references at 2.5, 5 and 10&nbsp;MHz, originally only occasionally during the day. At first, there were announcements every fifteen minutes, beginning with the Morse code representation of "MSF MSF MSF" (MSF is "-- ··· ··-·" in Morse code), followed by speech "This is MSF, Rugby, England, transmitting ...".<ref>{{cite web|title=NPL Time Reference FAQ|url=http://www.npl.co.uk/science-technology/time-frequency/time/faqs/what-does-msf-stand-for-(faq-time)|publisher=NPL|access-date=20 January 2014|archive-date=22 April 2014|archive-url=https://web.archive.org/web/20140422133514/http://www.npl.co.uk/science-technology/time-frequency/time/faqs/what-does-msf-stand-for-(faq-time)|url-status=live}}</ref> From May 1953, the signal was broadcast 24 hours a day, but with regular five-minute stoppages to allow the reception of other signals. The 60&nbsp;kHz signal finally became an uninterrupted 24-hour service in 1966, and the frequency references were discontinued in February 1988.<ref name="faqs" />
On 27 February 2007 the NPL started tests of the new time signal transmissions from [[Anthorn Radio Station|Anthorn]]{{coord|54.91|N|3.28|W|region:GB|display=title}}.<ref>{{cite news
| author = Kelly Eve
| title = Time Begins in Anthorn Village
| work = News & Star
| location = Carlisle
| date = 28 February 2007
| url = http://www.newsandstar.co.uk/news/viewarticle.aspx?id=471174
| access-date = 28 February 2007 |archive-url = https://web.archive.org/web/20070810033940/http://www.newsandstar.co.uk/news/viewarticle.aspx?id=471174 <!-- Bot retrieved archive --> |archive-date = 10 August 2007}}</ref> The Anthorn station was operated by [[VT Communications]] from its opening in 2007 until 2010, when it was acquired by [[Babcock International]].<ref name=siginfo>{{cite web|url=https://www.npl.co.uk/msf-signal|title=MSF Radio Time Signal|access-date=1 May 2022|publisher=[[National Physical Laboratory (United Kingdom)|National Physical Laboratory]]|archive-date=2019-07-05|archive-url=https://web.archive.org/web/20190705131618/https://www.npl.co.uk/msf-signal|url-status=live}} General and technical information, advice on reception problems, and up-to-date information on signal outages and scheduled maintenance</ref>
The formal inauguration of the relocated facility took place on 1 April 2007, when the name of the service became "The Time from NPL" and the signal from Rugby was permanently switched off.<ref>{{cite news
|title=Times changing for radio signal
|author=Pallab Ghosh
|work=BBC News Online
|date=10 May 2006
|url=http://news.bbc.co.uk/1/hi/sci/tech/4756593.stm
|access-date=28 March 2007
|archive-date=2 January 2007
|archive-url=https://web.archive.org/web/20070102110717/http://news.bbc.co.uk/1/hi/sci/tech/4756593.stm
|url-status=live
}}</ref><ref>{{cite news
|title=Time change marks end of an era
|work=BBC News Online
|date=25 March 2007
|url=http://news.bbc.co.uk/1/hi/sci/tech/6483969.stm
|access-date=28 March 2007
|archive-date=27 March 2007
|archive-url=https://web.archive.org/web/20070327132755/http://news.bbc.co.uk/1/hi/sci/tech/6483969.stm
|url-status=live
}}</ref> 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. This is found more in domestic equipment not designed for optimum sensitivity and positioned haphazardly.{{Citation needed|date=November 2011}}
Currently, the signal from Anthorn is still useable, in the location of the Mediterranean, although it is weaker than Rugby.
==The 'MSF signal' and the 'Rugby clock'==
From the time signal's inauguration in 1950 until 1 April 2007 it was transmitted from [[Rugby Radio Station]] near [[Rugby, Warwickshire]].<ref name="faqs">{{cite web|title=NPL T&F: FAQs|publisher=National Physical Laboratory, UK|access-date=23 January 2008|url=http://www.npl.co.uk/science-technology/time-frequency/time/faqs/|archive-date=6 June 2009|archive-url=https://web.archive.org/web/20090606074756/http://www.npl.co.uk/science-technology/time-frequency/time/faqs/|url-status=live}}</ref><ref name="moved" /> The transmitter's original location meant that the clock was referred to as "the Rugby clock".<ref>{{cite web | title = ARM+FPGA based Rugby clock | publisher = Computer Laboratory, University of Cambridge | access-date = 6 April 2007 | url = http://www.cl.cam.ac.uk/teaching/2005/ECADArch/lab6.html | archive-date = 2 June 2007 | archive-url = https://web.archive.org/web/20070602171616/http://www.cl.cam.ac.uk/teaching/2005/ECADArch/lab6.html | url-status = live }}</ref> Following its relocation in 2007 to Cumbria, the NPL now formally calls the signal "The Time from NPL".<ref name="moved" />
The Rugby transmitter's [[callsign]] was MSF, where 'M' is one of the [[ITU prefix]]es allocated to the United Kingdom, and the letters 'SF' were allocated for no documented reason. This resulted in the common terminology "the MSF signal", which is still used by the NPL.<ref name="faqs" /> 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".<ref>{{Cite web |url=http://www.subbrit.org.uk/sb-sites/sites/r/rugby_radio/indexr69.shtml |title=The Official History of Rugby Radio Station |access-date=2005-01-05 |archive-date=2004-12-14 |archive-url=https://web.archive.org/web/20041214065326/http://www.subbrit.org.uk/sb-sites/sites/r/rugby_radio/indexr69.shtml |url-status=live }}</ref> According to the NPL it seems the call sign was chosen so that it could be memorized as "Master Standard Frequency" but MSF was not intended to be an abbreviation.<ref>{{Cite web |url=http://www.npl.co.uk/science-technology/time-frequency/time/faqs/what-does-msf-stand-for-(faq-time) |title=NPL FAQ "What does MSF stand for?" |access-date=2014-01-20 |archive-date=2014-04-22 |archive-url=https://web.archive.org/web/20140422133514/http://www.npl.co.uk/science-technology/time-frequency/time/faqs/what-does-msf-stand-for-(faq-time) |url-status=live }}</ref>
==Transmission and reception==
The transmitted signal has an [[effective radiated power]] of 17 [[kilowatt|kW]], on a frequency of 60 [[kilohertz|kHz]] to within 2 parts in 10<sup>12</sup>.<ref name="nplmsf" /> The signal strength is greater than 10 mV/m at 100&nbsp;km (60 miles); it is greater than 100 μV/m at 1,000&nbsp;km (600 miles) from the transmitter, and thus can be received at not less than this strength throughout the UK.<ref name="moved">{{cite web|title=Time Has Moved |publisher=National Physical Laboratory, UK |access-date=6 April 2007 |url=http://www.npl.co.uk/time/msf/change.html |url-status=unfit |archive-url=https://web.archive.org/web/20070927004145/http://www.npl.co.uk/time/msf/change.html |archive-date=September 27, 2007 }}</ref> The signal can also be received, and is widely used, in northern and western Europe.<ref name="nplmsf" />
While at Rugby, the transmitter generated 60&nbsp;kW of [[radio frequency]] power (using 70&nbsp;kW of [[Mains electricity|mains power]]). The 180 metre-high (590') [[T-aerial]] antenna was 500 metres (1640') across at its top. The vertical part of the antenna radiated the signal, so that the received strength was similar in all directions (it was approximately [[Omnidirectional antenna|omnidirectional]]).<ref name="faqs" />
==Uses==
In addition to professional uses where accurate time is required, [[radio-controlled clock]]s (including wristwatches) with both digital and analog displays using the NPL signal are widely used. (Similar clocks are available in other regions with standard time transmissions.) As far as users are concerned they are simply clocks with the same features and settings as others, but always display the right time, and correct themselves for [[summer time]].
==Protocol==
===Fast code===
When MSF was first introduced, in 1950, it consisted only of seconds and minute markers, with no coded data. In 1974, a short burst of binary code at 100 bit/s was inserted into the minute marker to specify the time. In 1977, a slow code was introduced, which encoded the time at 1 bit/s over the whole minute (as detailed below). In 1998, the original fast code was removed, leaving the slow code and a simple minute marker.<ref>{{cite web|url=http://www.npl.co.uk/reference/faqs/what-is-the-msf-fast-code-(faq-time)|last=National Physical Laboratory|title=What is the MSF fast code? (FAQ-Time)|date=25 March 2010|access-date=22 September 2018|archive-date=22 September 2018|archive-url=https://web.archive.org/web/20180922140405/http://www.npl.co.uk/reference/faqs/what-is-the-msf-fast-code-(faq-time)|url-status=live}}</ref>
===Slow code===
Currently, the signal is encoded as follows:
The MSF transmitter is switched off for brief intervals ([[on-off keying]]) near the beginning of each second to encode the current time and date.  The rise and fall times of the 60&nbsp;kHz carrier are determined by the combination of antenna and transmitter.<ref name=NPLTFS>{{cite web
| title =MSF 60&nbsp;kHz Time and Date Code
| work =NPL Time and Frequency Services
| publisher =National Physical Laboratory
| date =July 2007
| url =http://www.npl.co.uk/upload/pdf/MSF_Time_Date_Code.pdf
| id =TAF001v06
| access-date =26 May 2008
| archive-date =28 July 2008
| archive-url =https://web.archive.org/web/20080728142443/http://www.npl.co.uk/upload/pdf/MSF_Time_Date_Code.pdf
| url-status =live
}}</ref>
Each UTC second begins with 100&nbsp;ms of 'off', preceded by at least 500&nbsp;ms of carrier.  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 [[UT1|Universal Time]] (UT1) which is the mean solar time which would actually be observed at 0° longitude.
The first [[second]] of the [[minute]], denoted second 00, begins with a period of 500 ms with the carrier off, to serve as a minute marker.
The other 59 (or, exceptionally, 60 or 58) seconds of the minute always begin with at least 100 ms 'off', followed by two data bits of 100&nbsp;ms each, and end with at least 700&nbsp;ms of carrier.
* Bit A is transmitted from 100 to 200 ms after the second
* Bit B is transmitted from 200 to 300&nbsp;ms after the second
Negative Polarity Bit Signalling
* <code>Carrier ON</code> represents a bit value of 0.
* <code>Carrier OFF</code> represents a bit value of 1.
If each second is considered as ten 100&nbsp;ms pieces, the minute marker is transmitted as <code>1111100000</code>, while all other seconds are transmitted as <code>1AB0000000</code>.
Although two data bits are transmitted per second, the time code has the property that only one of them is variable; non-zero B bits are only transmitted when the corresponding A bit has a fixed value.
Seconds 01–16 carry information for the current minute about the difference (DUT1) between atomic and astronomical time, and the remaining seconds convey the time and date code.
The time and date code information begins 43 seconds ''before'' the corresponding minute marker (second 17 of the previous minute, in the absence of [[leap seconds]]), and is always given in terms of UK civil time, which is UTC in winter and UTC+1h when [[British Summer Time|Summer Time]] is in effect.
{|class="wikitable" style="text-align:center"
|+ MSF time code<br />Shaded bits are fixed
! &nbsp;Bit&nbsp; !! &nbsp;A&nbsp; !! &nbsp;B&nbsp; !! Meaning
|rowspan=21|
! &nbsp;Bit&nbsp; !! &nbsp;A&nbsp; !! &nbsp;B&nbsp; !! Meaning
|rowspan=21|
! &nbsp;Bit&nbsp; !! &nbsp;A&nbsp; !! &nbsp;B&nbsp; !!colspan=2| Meaning
|-
| 00 ||bgcolor=lightblue| 1 ||bgcolor=lightblue| 1 ||bgcolor=lightblue| Minute mark
| 20 || 10 ||bgcolor=lightgrey| 0 ||rowspan=5| Year<br />(00–99)
| 40 || 10 ||bgcolor=lightgrey| 0 ||rowspan=5 colspan=2| Hour<br />(00–23)
|-
| 01 ||bgcolor=lightgrey| 0 || +0.1 ||rowspan=8| DUT1<br />(0.1–0.8)<br />[[Unary code|Unary encoding]],<br />bit set if<br />DUT1 ≥ Weight
| 21 || 8 ||bgcolor=lightgrey| 0
| 41 || 8 ||bgcolor=lightgrey| 0
|-
| 02 ||bgcolor=lightgrey| 0 || +0.2
| 22 || 4 ||bgcolor=lightgrey| 0
| 42 || 4 ||bgcolor=lightgrey| 0
|-
| 03 ||bgcolor=lightgrey| 0 || +0.3
| 23 || 2 ||bgcolor=lightgrey| 0
| 43 || 2 ||bgcolor=lightgrey| 0
|-
| 04 ||bgcolor=lightgrey| 0 || +0.4
| 24 || 1 ||bgcolor=lightgrey| 0
| 44 || 1 ||bgcolor=lightgrey| 0
|-
| 05 ||bgcolor=lightgrey| 0 || +0.5
| 25 || 10 ||bgcolor=lightgrey| 0 ||rowspan=5| Month<br />(01–12)
| 45 || 40 ||bgcolor=lightgrey| 0 ||rowspan=7 colspan=2| Minute<br />(00–59)
|-
| 06 ||bgcolor=lightgrey| 0 || +0.6
| 26 || 8 ||bgcolor=lightgrey| 0
| 46 || 20 ||bgcolor=lightgrey| 0
|-
| 07 ||bgcolor=lightgrey| 0 || +0.7
| 27 || 4 ||bgcolor=lightgrey| 0
| 47 || 10 ||bgcolor=lightgrey| 0
|-
| 08 ||bgcolor=lightgrey| 0 || +0.8
| 28 || 2 ||bgcolor=lightgrey| 0
| 48 || 8 ||bgcolor=lightgrey| 0
|-
| 09 ||bgcolor=lightgrey| 0 || −0.1 ||rowspan=8| DUT1<br />(−0.1–−0.8)<br />Unary encoding,<br />bit set if<br />DUT1 ≤ Weight
| 29 || 1 ||bgcolor=lightgrey| 0
| 49 || 4 ||bgcolor=lightgrey| 0
|-
| 10 ||bgcolor=lightgrey| 0 || −0.2
| 30 || 20 ||bgcolor=lightgrey| 0 ||rowspan=6| Day of month<br />(01–31)
| 50 || 2 ||bgcolor=lightgrey| 0
|-
| 11 ||bgcolor=lightgrey| 0 || −0.3
| 31 || 10 ||bgcolor=lightgrey| 0
| 51 || 1 ||bgcolor=lightgrey| 0
|-
| 12 ||bgcolor=lightgrey| 0 || −0.4
| 32 || 8 ||bgcolor=lightgrey| 0
| 52 ||bgcolor=lightpink| 0 ||bgcolor=lightgrey| 0 ||bgcolor=lightpink colspan=2| Minute marker 01111110
|-
| 13 ||bgcolor=lightgrey| 0 || −0.5
| 33 || 4 ||bgcolor=lightgrey| 0
| 53 ||bgcolor=lightpink| 1 || STW ||colspan=2| Summer time warning.
|-
| 14 ||bgcolor=lightgrey| 0 || −0.6
| 34 || 2 ||bgcolor=lightgrey| 0
| 54 ||bgcolor=lightpink| 1 || P1 || Year (17A–24A) ||rowspan=4|[[Odd parity|Odd<br />parity]]<br />over
|-
| 15 ||bgcolor=lightgrey| 0 || −0.7
| 35 || 1 ||bgcolor=lightgrey| 0
| 55 ||bgcolor=lightpink| 1 || P2 || Day (25A–35A)
|-
| 16 ||bgcolor=lightgrey| 0 || −0.8
| 36 || 4 ||bgcolor=lightgrey| 0 ||rowspan=3| Day of week<br />Sunday=0<br />Saturday=6
| 56 ||bgcolor=lightpink| 1 || P3 || DOW (36A–38A)
|-
| 17 || 80 ||bgcolor=lightgrey| 0 ||rowspan=3| Year (00–99)
| 37 || 2 ||bgcolor=lightgrey| 0
| 57 ||bgcolor=lightpink| 1 || P4 || Time (39A–51A)
|-
| 18 || 40 ||bgcolor=lightgrey| 0
| 38 || 1 ||bgcolor=lightgrey| 0
| 58 ||bgcolor=lightpink| 1 || ST ||colspan=2| Summer time in effect.
|-
| 19 || 20 ||bgcolor=lightgrey| 0
| 39 || 20 ||bgcolor=lightgrey| 0 || Hour (00–23)
| 59 ||bgcolor=lightpink| 0 ||bgcolor=lightgrey| 0 ||bgcolor=lightgrey colspan=2| Unused, always 0.
|}
Consecutive bits from 01B–08B are set to 1 to indicate positive DUT1 values from +0.1s to +0.8s.  For example, bit 05B is set if DUT1 ≥ 0.5 s.  Consecutive bits from 09B–16B are set to 1 to indicate negative DUT1 values from −0.1s to −0.8s.  For example, bit 11B is set if DUT1 ≤ −0.3 s.
In case of a leap second, a zero bit is inserted between seconds 16 and 17.<ref name=NPLTFS />  In case of a negative leap second, second 16 will be deleted.  Since negative leap seconds can only occur when DUT1 is positive, bits 9B through 16B will be zero.
Bits 17A–51A encode the time of the following minute in [[binary-coded decimal]], most significant bit first.  Beginning with bit 17A comes 4 bits of tens of years, 4 bits of years, 1 bit of tens of months, 4 bits of months, 2 bits of tens of days, 4 bits of days, 3 bits of day of week (0=Sunday), 2 bits of tens of hours, 4 bits of hours, 3 bits of tens of minutes, and 4 bits of minutes.
Bits 52A–59A provide another way to identify minute boundaries.  This sequence <code>01111110</code> never appears elsewhere in the A bits; due to BCD encoding, at most five consecutive 1 bits can appear elsewhere in the A bits (bits 27A–31A, on July 30 or 31, or bits 33A–37A, if a day ending in 7 falls on a Saturday).  These six consecutive 1 bits thus uniquely identify the end of the minute.
Bits 54B–57B provide [[odd parity]] over the time code.  The 4 parity bits cover years (8 bits), months and days (11 bits), day of week (3 bits), and time of day (13 bits) respectively.
Bit 58B indicates the broadcast time is summer time.  Bit 53B gives warning that the summer time bit is about to change.  It is set for 61 consecutive minutes, starting 1 hour 7 seconds before the change, and ending 7 seconds before the change, 5 seconds before the first changed bit 58B, which is itself transmitted 2 seconds (1.7–1.8 seconds, to be more precise) before the moment of the time change.
=== Shortcomings of the current signal format ===
MSF does not broadcast any explicit advance warning of upcoming [[leap second]]s, which occur less than once a year on average.<ref name="TROGER" />  The only indication is a change in the number of padding bits before the time code during the minute before the leap second.  Therefore, unless a leap-second announcement is manually entered into a receiver in advance, it may take some time until an autonomous MSF receiver regains synchronization with UTC after a leap second (especially if the reception is not robust at the time of the leap second).
Like DCF77, the time signal only provides 1 hour warning of summer-time changes.<ref name=NPLTFS />
== Outages ==
MSF normally broadcasts continuously, but is occasionally taken out of service for scheduled or unscheduled maintenance. The ''Time from NPL'' Web site reports upcoming scheduled maintenance outages, and information on unscheduled outages.<ref name=siginfo/>
== See also ==
*[[Greenwich Time Signal]]
*[[Coordinated Universal Time]]
==References==
{{reflist}}
==External links==
* [http://www.subbrit.org.uk/sb-sites/sites/r/rugby_radio/indexr69.shtml The Official History of Rugby Radio Station]
* [https://web.archive.org/web/20061015113611/http://www.alan.melia.btinternet.co.uk/rugbyrs.htm A History of Rugby Radio, M Johnston, 1976] History from 1910.
* [https://web.archive.org/web/20070927004250/http://www.npl.co.uk/time/msf/msf_anthorn_news_release.pdf Press release about MSF relocation to Anthorn]
* [https://web.archive.org/web/20071031013926/http://www.clockco.co.uk/documents/msf.pdf National Physical Laboratory – public information leaflet about relocation]
* [http://www.npl.co.uk/science-technology/time-frequency/products-and-services/time/msf-radio-time-signal National Physical Laboratory – MSF Radio Time Signal]
* [http://www.npl.co.uk/science-technology/time-frequency/products-and-services/time/msf-outages National Physical Laboratory – MSF Outages]
{{Time signal stations}}
{{Time signal authorities}}
{{Time topics}}
{{Time measurement and standards}}
{{DEFAULTSORT:Time From Npl}}
[[Category:Time signal radio stations]]
[[Category:Time in the United Kingdom]]
[[Category:Call signs]]
[[Category:National Physical Laboratory (United Kingdom)]]