View source for Time signal

{{short description|Signal used as a reference to determine the time of day}}
{{Use dmy dates|date=January 2020}}
{{broader|Time standard}}
[[File:Time clocks-1905.jpg|frame|These automatic signal clocks were [[synchronization|synchronized]] by [[telegraphy]] in 1905 before the widespread use of radio]]
A '''time signal''' is a visible, audible, mechanical, or electronic [[signal]] used as a reference to determine the [[time of day]].

[[Church bell]]s or voices announcing hours of [[prayer]] gave way to automatically operated [[wikt:chime|chime]]s on public [[clock]]s; however, audible signals (even signal guns) have limited range. Busy [[Port|seaports]] used a visual signal, the dropping of a ball, to allow mariners to check the chronometers used for navigation. The advent of electrical [[telegraph]]s allowed widespread and precise distribution of time signals from central observatories. [[Railway]]s were among the first customers for time signals, which allowed synchronization of their operations over wide geographic areas. Dedicated radio time signal stations transmit a signal that allows automatic synchronization of clocks, and commercial broadcasters still include time signals in their programming.

Today, global navigation satellite systems ([[GNSS]]) radio signals are used to precisely distribute time signals over much of the world. There are many commercially available [[Radio clock|radio controlled clocks]] available to accurately indicate the local time, both for business and residential use. Computers often set their time from an [[time server|Internet atomic clock source]]. Where this is not available, a locally connected GNSS receiver can precisely set the time using one of several software applications.

==Audible and visible time signals==

One sort of public time signal is a [[striking clock]].  These clocks are only as good as the clockwork that activates them, but they have improved substantially since the first clocks from the 14th century.  Until modern times, a public clock such as [[Clock Tower, Palace of Westminster|Big Ben]] was the only time standard the general public needed.

Accurate knowledge of time of day is essential for [[navigation]], and ships carried the most accurate [[marine chronometer]]s available, although they did not keep perfect time. A number of accurate audible or visible time signals were established in many [[seaport]] cities to enable navigators to set their chronometers.

=== Signal guns ===

In [[Vancouver]], [[British Columbia]], a "[[9 O'Clock Gun]]" is still shot every night at 9&nbsp;pm.  (This gun was brought to [[Stanley Park]] in 1894 by the [[Fisheries and Oceans Canada|Department of Fisheries]] originally to warn [[fishermen]] of the 6:00&nbsp;pm Sunday closing of fishing.) The 9:00&nbsp;pm firing was later established as a time signal for the general population. Until a time gun was installed, the nearby [[Brockton Point]] lighthouse keeper detonated a stick of dynamite. Elsewhere in Canada, a "Noon Gun" is fired daily from the citadels in [[Citadel Hill (Fort George)|Halifax]] and [[Citadelle of Quebec|Quebec City]] and from [[Signal Hill, St. John's|Signal Hill]] in [[St. John's, Newfoundland and Labrador]].<ref>{{Cite web|url=https://www.pc.gc.ca/en/lhn-nhs/nl/signalhill/activ/activ-and-exp/Noon-Day-Gun|title=Noon Day Gun - Signal Hill National Historic Site|first=Government of Canada|last=Parks Canada Agency|date=10 April 2019|website=www.pc.gc.ca}}</ref>

In the same manner, a [[Noon Gun]] has been fired in [[Cape Town]], since 1806.<ref>{{cite web|url=http://www.bokaap.co.za/noon-gun/|title=Noon Gun -|website=bokaap.co.za|access-date=8 April 2018}}</ref> The gun is fired daily from the Lion Battery at [[Signal Hill (Cape Town)|Signal Hill]].

The [[Noonday Gun]] serves a similar purpose in [[Hong Kong]]. The tradition, which started in the 1860s under British colonial rule, has become a tourist attraction in recent times. 

A cannon was fired at one o'clock every weekday at [[Liverpool]], at the [[Edinburgh Castle|Castle]] in [[Edinburgh]], and also at [[Perth Observatory|Perth]] to establish the time. The Edinburgh "[[One O'Clock Gun]]" is still in operation. A cannon located at the top of Santa Lucia Hill, in [[Santiago]], is shot every noon.

In [[Rome]], on the [[Janiculum]], a hill west of the [[Tiber]] since 1904 a cannon is fired daily at noon towards the river as a time signal. This was introduced in 1847 by [[Pope Pius IX]] to synchronise all the church bells of Rome. It was situated in [[Castel Sant'Angelo]] until 1903 when it was moved to [[Monte Mario]] for a few months until it was placed in its current position. The cannon was silenced from the start of [[WWII]] for about twenty years until 21 April 1959, the 2712th anniversary of Rome's founding, and has been in use since then.

For many years an old cannon was fired "about noon" from a mountain near [[Kabul]].<ref>{{cite journal|url=https://www.csmonitor.com/1982/0422/042212.html|title=The noon gun|date=22 April 1982|access-date=8 April 2018|journal=Christian Science Monitor}}</ref><ref>{{cite web|url=http://www.digitalsilver.co.uk/TimeGun/kabul_gun.html|title=The Old Noon Day Gun of Kabul - Afghanistan|website=digitalsilver.co.uk|access-date=8 April 2018|archive-date=28 August 2017|archive-url=https://web.archive.org/web/20170828020350/http://www.digitalsilver.co.uk/TimeGun/kabul_gun.html|url-status=dead}}</ref>

=== Sirens, whistles, and other audible signals ===

In many Midwestern US cities where tornadoes are a common hazard, the [[emergency siren]]s are tested regularly at a specified time (say, noon each Saturday); while not primarily intended to mark the time, local people often check their watches when they hear this signal. In many non-seafaring communities, loud factory [[whistle]]s served as public time signals before radio made them obsolete. Sometimes, the tradition of a factory whistle becomes so deeply entrenched in a community that the whistle is maintained long after its original function as a time keeper became obsolete.<ref>{{cite news |last1=Ross |first1=Jenna |title=Midwestern towns with sirens weigh nostalgia against nuisance |url=http://www.startribune.com/towns-with-daily-sirens-balance-nostalgia-nuisance/288938591/ |access-date=21 June 2018 |work=Minneapolis Star Tribune |date=9 April 2015}}</ref> For example, the [[University of Iowa]]'s power plant whistle has been reinstated several times by popular demand after numerous attempts to silence it.<ref>{{cite news |last1=Snee |first1=Tom |title=The enduring exhalations of The Whistle |url=https://fyi.uiowa.edu/04/18/the-whistle/ |access-date=21 June 2018 |work=Iowa Now |date=18 April 2011 |archive-date=22 June 2018 |archive-url=https://web.archive.org/web/20180622005411/https://fyi.uiowa.edu/04/18/the-whistle/ |url-status=dead }}</ref>

=== Visual signals ===
[[File:Royal observatory greenwich.jpg|thumb|right|The [[time ball]] on the roof of [[Greenwich Observatory]], London]]
In 1861 and 1862, the Edinburgh Post Office Directory published time gun [[map]]s relating the number of seconds required for the report of the time gun to reach various locations in the city. Because [[speed of light|light]] travels much faster than [[speed of sound|sound]], visible signals enabled greater precision than audible ones, although audible signals could operate better under conditions of reduced visibility. The first [[time ball]] was erected at [[Portsmouth]], England in 1829 by its inventor [[Robert Wauchope (admiral)|Robert Wauchope]].<ref name=AUB>Aubin, David [https://books.google.com/books?id=9EKzLQL3RQEC&dq=Robert+Wauchope+time+ball&pg=PA164 The Heavens on Earth: Observatories and Astronomy in Nineteenth-Century Science and Culture] p.164. Duke University Press, 2010</ref> One was installed in 1833 on the roof of the [[Royal Greenwich Observatory|Royal Observatory]] in [[Greenwich]], London, and the time ball has dropped at 1:00 pm every day since then.<ref>{{cite web|url=http://wwp.greenwichmeantime.co.uk/info/timeball.htm|title=Greenwich Time Ball|website=greenwichmeantime.co.uk|access-date=8 April 2018|url-status=dead|archive-url=https://web.archive.org/web/20101023194034/http://wwp.greenwichmeantime.co.uk/info/timeball.htm|archive-date=23 October 2010}}</ref> The first American time ball went into service in 1845.<ref name=AUB/> In New York City, the ceremonial [[Times Square Ball]] drop on New Year's Eve in [[Times Square]] is a vestige of a visual time signal.

==Electrical time signals==
=== United Kingdom ===
The first telegraph distribution of time signal in the United Kingdom, indeed, in the world, was initiated in 1852 by the [[Electric Telegraph Company]] in collaboration with the [[Astronomer Royal]].  [[Greenwich Mean Time]] was distributed by telegraph from the [[Greenwich Observatory]].  This included a system for synchronising the drop of the time ball at Greenwich with other time balls around the country, one of which was atop the Electric's offices in the [[Strand, London|Strand]].<ref name=Kieve52/>

Other synchronised time balls were atop the [[Nelson Monument, Edinburgh]]; the sailors' home [[Broomielaw]], Glasgow; [[Liverpool]] and one at [[Deal, Kent]], installed by the [[British Admiralty|Admiralty]].<ref name=Kieve52>Kieve, Jeffrey L., ''The Electric Telegraph: A Social and Economic History'', pp. 52-53, David and Charles, 1973 {{oclc|655205099}}.</ref>

=== United States ===
Telegraph signals were used regularly for time coordination by the [[United States Naval Observatory]] starting in 1865.<ref>{{Cite web |url=http://tycho.usno.navy.mil/history.html |title=Timekeeping at the U.S. Naval Observatory |access-date=10 April 2018 |archive-date=19 December 2017 |archive-url=https://web.archive.org/web/20171219093942/http://tycho.usno.navy.mil/history.html |url-status=dead }}</ref> By the late 1800s, many U.S. observatories were selling accurate time by offering a regional time signal service.<ref>{{cite book |last=Bartky |first=Ian R. |date=2000 |title=Selling the true time |url=https://archive.org/details/sellingtruetimen00bart_0 |url-access=registration |publisher=Stanford University Press |page=[https://archive.org/details/sellingtruetimen00bart_0/page/199 199] |isbn=9780804738743 |access-date=29 March 2019 }}</ref>

[[Sandford Fleming]] proposed a single 24-hour clock for the entire world. At a meeting of the Royal Canadian Institute on 8 February 1879 he linked it to the [[Prime meridian (Greenwich)|anti-meridian of Greenwich]] (now 180°). He suggested that standard [[time zone]]s could be used locally, but they were subordinate to his single world time.

[[File:Standard Time from Ladd Observatory.png|thumb|Advertisement for a telegraph time signal service (1900)]]
[[Standard time]] came into existence in the United States on 18 November 1883.  Earlier, on 11 October 1883, the General Time Convention, forerunner to the [[American Railway Association]], approved a plan that divided the United States into several [[time zone]]s.  On that November day, the US Naval Observatory telegraphed a signal that coordinated noon at Eastern standard time with 11&nbsp;am Central, 10&nbsp;am Mountain, and 9&nbsp;am Pacific standard time.

A March 1905 issue of ''The Technical World'' describes the role of the United States Naval Observatory as a source of time signals:

:''One of the most important functions of the Naval Observatory is found in the daily distribution of the correct time to every portion of the United States. This is effected by means of telegraphic signals, which are sent out from Washington at noon daily, except Sundays. The original object of this time service was to furnish mariners in the seaboard cities with the means of regulating their chronometers; but, like many another governmental activity, its scope has gradually broadened until it has become of general usefulness. The electrical impulse which goes forth from the Observatory at noon each day, now sets or regulates automatically more than 70,000 clocks located in all parts of the United States, and also serves, in each of the larger cities of the country, to release a time-ball located on some lofty building of central location. The dropping of the time-ball – accompanied, at some points, with the simultaneous firing of a cannon – is the signal for the regulation by hand of hundreds of other clocks and watches in the vicinity.''

== <span class="anchor" id="radio_time_anchor"></span> Radio time sources ==
{{See also|Radio clock#List of radio time signal stations}}
[[File:Atomic clock.jpg|thumb|245px|A modern [[Low frequency|LF]] [[Radio clock]]]]

===Dedicated time signal broadcasts===
The telegraphic distribution of time signals was made obsolete by the use of AM, FM, [[shortwave radio]], Internet [[Network Time Protocol]] [[Server (computing)|servers]] as well as [[atomic clock]]s in [[Satellite Navigation|satellite navigation]] systems. Time signals have been transmitted by radio since 1905.<ref name=Burns04>{{cite book | first=R.W. | last=Burns | title=Communications: An international history of the formative years | publisher=IET | year=2004 | isbn=0863413277 | page=121 }}</ref> There are dedicated [[Radio clock#List of radio time signal stations|radio time signal stations]] around the world.

Time stations operating in the [[longwave]] radio band have highly predictable [[radio propagation]] characteristics, which gives low uncertainty in the received time signals. Stations operating in the [[shortwave]] band can cover wider areas with relatively low-power transmitters, but the varying distance that the signal travels increases the uncertainty of the time signal on a scale of milliseconds.<ref name=McCarthy-Seidelmann-2009>{{cite book |first1=Dennis D. |last1=McCarthy |first2=P. Kenneth |last2=Seidelmann |year=2009 |title=Time: From Earth rotation to atomic physics |publisher=Wiley-VCH |isbn=978-3-527-40780-4 |page=256}}</ref>

Radio time signal stations broadcast the time in both audible and machine-readable [[time code]] form that can be used as references for [[radio clock]]s and [[Watch#Electronic|radio-controlled watches]]. Typically, they use a national or regional [[longwave]] digital signal; for example, station [[WWVB]] in the U.S.&nbsp;.<ref name=McCarthy-Seidelmann-2009/>

The audio portions of the shortwave [[WWV (radio station)|WWV]] and [[WWVH]] broadcasts can also be heard by telephone. The time announcements are normally delayed by less than 30&nbsp;ms when using land lines from within the continental United States, and the stability (delay variation) is generally {{nobr|less than 1 ms.}} However, when [[mobile phones]] are used, the delays are often more than 100&nbsp;ms, due to the multiple access methods used to share cell channels. In rare instances when the telephone connection is made by satellite, the time is delayed by 250–500&nbsp;ms.

The audio from the broadcasts is available by telephone by dialling U.S. numbers {{nobr|(303) 499-7111}} for [[WWV (radio station)|WWV]] (Colorado), and {{nobr|(808) 335-4363}} for [[WWVH]] (Hawaii). Calls (which are ''not'' toll-free) are disconnected after 2&nbsp;minutes.
[[File:Low cost DCF77 receiver.jpg|thumb|A low cost [[Low frequency|LF]] [[radio clock]] receiver, antenna left, receiver right.]]

[[Loran-C]] time signals formerly were also used for radio clock synchronization, by augmenting their highly accurate frequency transmissions with external measurements of the offsets of LORAN navigation signals against time standards.

===General broadcasters===
As radio receivers became more widely available, broadcasters included time information in the form of voice announcements or automated tones to accurately indicate the hour. The [[BBC]] has included time "[[Greenwich Time Signal|pips]]" in its broadcasts from 1922.<ref name=Burns04/>

In the United States many information-based radio stations (full-service, all-news and news/talk) also broadcast time signals at the beginning of the hour. In New York, [[WCBS (AM)|WCBS]] and [[WINS (AM)|WINS]] have distinctive beginning-of-the-hour tones, though the WINS signal is only approximate (several seconds error).{{Citation needed|date=March 2018|reason=Is this possibly due to lack of correction for the delay for HD Radio?  Typically stations employing HD Radio delay analog transmission so that if a receiver is hopping between HD and analogue the audio will be roughly synchronized. Many radio stations need to join and leave a network so their time is usually pretty accurate.}} WINS also has a tone at 30&nbsp;minutes past the hour for those setting their clocks. [[WTIC-AM|WTIC]] uses the [[Morse code]]&nbsp;V for victory to the tune of [[Beethoven's 5th Symphony]] at the beginning of the hour continuously, since 1943.

Broadcast stations using iBiquity Digital's "[[HD Radio]]" system are contractually required<ref>{{cite report |title=Licensing fact sheet 2009 |publisher=iBiquity Digital Corporation |url=http://www.ibiquity.com/i/Licensing_%20Fact_%20Sheet_2009.pdf |via=ibiquity.com |archive-url=https://web.archive.org/web/20110713000748/http://www.ibiquity.com/i/Licensing_%20Fact_%20Sheet_2009.pdf |archive-date=13 July 2011 }}</ref> to delay their analog broadcast by about eight seconds, so it remains in sync with the digital stream. Thus, network-generated time signals and service cues will also be delayed by about eight seconds. (Because of the delay, when [[WBEN (AM)|WBEN-AM]] in [[Buffalo, New York]] was broadcasting time markers, and was simulcast on an FM station that broadcast in HD; the FM signal did not carry the time signal. WBEN does not broadcast in HD.) Local signals may also be delayed.

The [[all-news radio]] stations of the [[CBS Radio Network]], of which WCBS is the flagship, air a "bong" (at a frequency of 440&nbsp;Hz – the international standard for the [[A440 (pitch standard)|musical note {{sc|'''A'''}} ]]) that immediately precedes each top-of-the-hour network newscast. (The same bong could be heard on the [[CBS]] Television Network, at the top of the hour immediately before the beginning of any televised program, in the 1960s and 1970s.) An automated "chirp" at one second before the hour signals a switch to the radio network broadcast. As an example, [[KNX (AM)|KNX]], the CBS Radio Network all-news station in Los Angeles, broadcasts this "bong" sound on the hour. However, due to buffering of the digital broadcast on some computers, this signal may be delayed as much as 20&nbsp;seconds from the actual start of the hour (this is presumably the same situation for all CBS Radio stations, as each station's digital stream is produced and distributed in a similar manner), though unlike program content which is on a [[broadcast delay]] for content concerns, the time signal airs as-is over-the-air, meaning it can sometimes be talked over during a live news event or sports play-by-play. [[KYW-AM]] in Philadelphia broadcasts a time signal at the top of the hour along with its [[jingle]].

[[Bonneville International]]-owned news/talk station [[KSL (radio)|KSL]] (AM-FM) in Salt Lake City uses a "clang" that originates from the Nauvoo Bell on Temple Square, in Salt Lake City, which has been a staple on the station since the early 1960s.

In Canada, the national English-language non-commercial [[CBC Radio One]] network broadcast the daily [[National Research Council Time Signal]] from 5&nbsp;November 1939<ref>{{cite news |first=Geoff |last=Bartlett |date=5 November 2014 |title='The beginning of the long dash' indicates 75&nbsp;years of official time on CBC |website=[[CBC News]] (cbc.ca) |url=http://www.cbc.ca/news/canada/newfoundland-labrador/the-beginning-of-the-long-dash-indicates-75-years-of-official-time-on-cbc-1.2823599 |access-date=8 April 2018}}</ref> until 9&nbsp;October 2023.<ref name=cancel>{{cite news |last1=Taekema |first1=Dan |date=10 October 2023 |title=The end of the long dash: CBC stops broadcasting official 1&nbsp;{{sc|p.m.}} time signal |website=[[CBC News]] (cbc.ca) |url=https://www.cbc.ca/news/canada/ottawa/cbc-stops-broadcasting-national-research-council-long-dash-time-signal-1.6988903 |access-date=2 December 2023 }}</ref> The simulcast would occur daily at 1pm [[Eastern Time]]. Its French-language counterpart, [[Canadian Broadcasting Corporation|Radio-Canada]], broadcasts a similar signal at noon. [[Vancouver]] radio station [[CKNW]] also broadcasts time signals, using a chime every half-hour. Time signals on CBC broadcasts may be delayed up to 3&nbsp;seconds due to network processing delays between the local radio transmitter and the time signal origin in Ottawa. The CBC's predecessor, the [[CNR Radio|Canadian National Railways Radio network]], broadcast the time signal over its [[CBO-FM|Ottawa station]], CNRO (originally CKCH), at 9 pm daily and also on its Moncton station, CNRA, beginning in 1923. CNRA closed in 1931 but the broadcasts continued on CNRO when the station was acquired by the [[Canadian Radio Broadcasting Commission]] in 1933 and by the CBC in 1936 before going national in 1939.<ref>{{cite news |title=The beginning of the long dash |year=1939 |series=CBC Archives |website=[[CBC News]] (cbc.ca) |url=http://www.cbc.ca/archives/categories/science-technology/measurement/general-5/1939-the-beginning-of-the-long-dash.html |access-date=8 April 2018 <!-- as of January 2024 --> |archive-date=8 June 2016 |archive-url=https://web.archive.org/web/20160608070931/http://www.cbc.ca/archives/categories/science-technology/measurement/general-5/1939-the-beginning-of-the-long-dash.html |url-status=dead }}</ref>

In Australia, many information-based radio stations broadcast time signals at the beginning of the hour, and a [[Speaking clock#Australia|speaking clock]] service was also available until October&nbsp;2019.  However, the [[Radio VNG|VNG]] dedicated time signal service has been discontinued.<ref>{{cite report |first1=Alfred |last1=Kruijshoop |first2=Marjorie |last2=Walker |section=Introduction |title=Time NZ & A |url=http://tufi.alphalink.com.au/time |archive-url=https://archive.today/20121230125806/http://tufi.alphalink.com.au/time/time_hf.html |url-status=dead |archive-date=30 December 2012 |via=tufi.alphalink.com.au |access-date= 23 November 2013 }}</ref>

In Cuba, [[Radio Reloj]] is a radio station which has a time signal over news. Radio Reloj translates to Clock Radio.

===Digital delay===

Program material, including time signals, that is transmitted digitally (e.g. [[Digital audio broadcasting|DAB]], [[Internet radio]]) can be delayed by tens of seconds due to buffering and error correction, making time signals received on a digital radio unreliable when accuracy is needed.

==See also==
{{div col begin|colwidth=17em}}
* [[Car radio]], [[Radio Data System]] (RDS)
* [[Clock signal]]
* [[Extended Data Services]] and PBS
* {{section link|Global Positioning System|Timekeeping}}
* [[Greenwich Time Signal]]
* [[Low frequency]], (LF)
* [[Smart Personal Objects Technology]], (SPOT)
* [[Speaking clock]]
* [[Synchronization]]
* [[Vertical blanking interval|VBI]], [[VITC]]
* [[WWVB]]
* [[Time synchronization in North America]]
* [[Time transfer]]
* [[Time and frequency transfer]]
* [[Time synchronization]]
{{div col end}}

==References==
{{reflist|25em}}

== Further reading ==
* {{cite book |last=Downing |first=Michael |year=2005 |title=Spring Forward: The annual madness of Daylight Saving Time |publisher=Shoemaker and Hoard |isbn=1-59376-053-1 }}

==External links==
*{{cite web
 |title       = The Time Ball and the One O'clock Gun
 |year        = 2007
 |publisher   = Proudman Oceanographic Laboratory
 |place       = Liverpool, UK
 |url         = http://www.pol.ac.uk/home/history/gun.html
 |access-date = 2 June 2008
 |url-status  = dead
 |archive-url = https://web.archive.org/web/20070927202715/http://www.pol.ac.uk/home/history/gun.html
 |archive-date = 27 September 2007
}}
* {{cite web
 |title=Perth
 |department=Travel in Western Australia
 |website=Travel Downunder
 |url=http://www.traveldownunder.com.au/Western_Australia/Perth/Round_House_Precinct,_The.asp 
 |archive-url=https://web.archive.org/web/20050702090321/http://www.traveldownunder.com.au/Western_Australia/Perth/Round_House_Precinct,_The.asp
 |archive-date=2 July 2005
}} — mentions the time cannon at [[Perth, Western Australia|Perth]]
* {{cite web
 |title=Noon Gun
 |department=Durr Cannon / Research Projects
 |website=museums.org.za
 |place=South Africa
 |url=http://www.museums.org.za/cannon/prod02.htm#Noon%20Gun 
 |archive-url=https://web.archive.org/web/20090107011426/http://www.museums.org.za/cannon/prod02.htm#Noon%20Gun
 |archive-date=7 January 2009
}} — mentions the time cannon at [[Cape Town, South Africa|Cape Town]]
* {{cite web
 |title=The VNG User's Consortium
 |website=tufi.alphalink.com.au
 |place=Australia
 |url=http://tufi.alphalink.com.au/time
|archive-url=https://archive.today/20121230125806/http://tufi.alphalink.com.au/time/time_hf.html
|url-status=dead
|archive-date=30 December 2012
}}  — The VNG Users' Consortium was working on ways to solve the problem of the lack of accurate time signals in Australia.
* {{cite web
 |title=The Edinburgh time gun
 |website=edinphoto.org.uk
 |place=Scotland
 |url=http://www.edinphoto.org.uk/1_edin/1_edinburgh_history_-_time-gun.htm
}}
* {{cite magazine
 |first=Waldon |last=Fawcett
 |date=March 1905
 |title=Distribution of time signals
 |magazine=The Technical World
 |volume=3  |number=1  |pages=19–26
 |oclc=9990027
<!--
 |publisher=[[Armour Institute of Technology]]
 |place=Chicago, IL
 -->
 |url=https://babel.hathitrust.org/cgi/pt?id=hvd.32044048683098;view=1up;seq=27
 |via=babel.hathitrust.org  |access-date=2 January 2024  |quote=Many-sided activities of the [[U.S. Naval Observatory]] at Washington, DC – the determination of time and other important astronomical work.}}
:
:: ''Magazine was published from 1904–1905 by the [[Armour Institute of Technology]].''
* {{cite web
 |title=Distributed time service: An upgrade to current time station technology
 |website=hireme.geek.nz
 |place=New Zealand
 |url=http://hireme.geek.nz/distributed-time-service.html
 |url-status=dead
 |access-date=13 December 2006
 |archive-date=27 September 2007
 |archive-url=https://web.archive.org/web/20070927150211/http://hireme.geek.nz/distributed-time-service.html
 }}
* {{cite web
 |last=Hacko
 |first=Nick, VK2DX
 |title=Receiving, identifying and decoding time signals
 |website=GenesisRadio.com.au
 |place=Australia
 |url=http://genesisradio.com.au/VK2DX/time_signals.html
 |url-status=dead
 |access-date=28 September 2011
 |archive-date=24 April 2012
 |archive-url=https://web.archive.org/web/20120424231038/http://genesisradio.com.au/VK2DX/time_signals.html
 }}

{{TimeSig}}
{{Time Topics}}
{{Time measurement and standards}}

[[Category:Time signal radio stations| ]]
[[Category:Time signals| ]]
[[Category:Horology]]