Time signal

Time signal

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A time signal is a visible, audible, mechanical, or electronic signal used as a reference to determine the time of day.

Audible and visible time signals


One sort of public time signal is, of course, a striking clock
Striking clock
A striking clock is a clock that sounds the hours audibly on a bell or gong. In 12 hour striking, used most commonly in striking clocks today, the clock strikes once at 1 AM, twice at 2 AM, continuing in this way up to twelve times at 12 noon, then starts over, striking once at 1 PM, twice at 2...

. These clocks, however, are only as good as the clockwork that activates them; they have improved substantially since the first surviving clocks from the 14th century. For many members of the general public, a public clock such as Big Ben
Clock Tower, Palace of Westminster
Big Ben is the nickname for the great bell of the clock at the north end of the Palace of Westminster in London, and is generally extended to refer to the clock or the clock tower as well. It is the largest four-faced chiming clock and the third-tallest free-standing clock tower in the world...

 was the only time standard they needed.

When more accurate public time signals were desired for use in navigation
Navigation
Navigation is the process of monitoring and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks...

, a number of traditional audible or visible time signals were established for the purpose of allowing navigators to check their marine chronometer
Marine chronometer
A marine chronometer is a clock that is precise and accurate enough to be used as a portable time standard; it can therefore be used to determine longitude by means of celestial navigation...

s. These public time signals were formerly established in many seaport cities.

As an example of such a signal, in Vancouver
Vancouver
Vancouver is a coastal seaport city on the mainland of British Columbia, Canada. It is the hub of Greater Vancouver, which, with over 2.3 million residents, is the third most populous metropolitan area in the country,...

, British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...

, a "9 O'Clock Gun
9 O'Clock Gun
The 9 O'Clock Gun is a cannon located in Vancouver, British Columbia that is shot every night at 21:00 PT. The crests of King George III and Henry Phipps, 1st Earl of Mulgrave, Master-General of the Ordnance at the time the cannon was cast, are on the barrel.The gun is a 12-pound muzzle-loaded...

" is still shot every night at 9 pm. This gun was brought to Stanley Park
Stanley Park
Stanley Park is a 404.9 hectare urban park bordering downtown Vancouver, British Columbia, Canada. It was opened in 1888 by David Oppenheimer in the name of Lord Stanley of Preston, the Governor-General of Canada....

 by the Department of Fisheries
Fisheries and Oceans Canada
Fisheries and Oceans Canada, frequently referred to as DFO , is the department within the government of Canada that is responsible for developing and implementing policies and programs in support of Canada's economic, ecological and scientific interests in oceans and inland waters...

 in 1894 to warn fishermen of the 6:00 pm Sunday closing of fishing. The 9:00 pm firing was later established as a time signal for the general population. The Brockton Point
Brockton Point
Brockton Point is located in Vancouver harbour at the east end of Stanley Park. It is named after Francis Brockton. Brockton Point Lighthouse, an automated light, is located at the point....

 lighthouse keeper, William D. Jones, originally detonated a stick of dynamite until the Time Gun was installed. A similar "Noon Gun
Noon Gun
The Noon Gun has been an historic time signal in Cape Town, South Africa since 1806. The gun is situated on Signal Hill, close to the centre of the city.- History :...

" is still shot every noon at Cape Town
Cape Town
Cape Town is the second-most populous city in South Africa, and the provincial capital and primate city of the Western Cape. As the seat of the National Parliament, it is also the legislative capital of the country. It forms part of the City of Cape Town metropolitan municipality...

, South Africa, as well as at the Citadelle of Quebec
Citadelle of Quebec
The Citadelle — the French name is used both in English and French — is a military installation and official residence located atop Cap Diamant, adjoining the Plains of Abraham in Quebec City, Quebec, Canada...

. A cannon was shot at one o'clock every weekday at Liverpool
Liverpool
Liverpool is a city and metropolitan borough of Merseyside, England, along the eastern side of the Mersey Estuary. It was founded as a borough in 1207 and was granted city status in 1880...

, England, at the Castle
Edinburgh Castle
Edinburgh Castle is a fortress which dominates the skyline of the city of Edinburgh, Scotland, from its position atop the volcanic Castle Rock. Human habitation of the site is dated back as far as the 9th century BC, although the nature of early settlement is unclear...

 in Edinburgh
Edinburgh
Edinburgh is the capital city of Scotland, the second largest city in Scotland, and the eighth most populous in the United Kingdom. The City of Edinburgh Council governs one of Scotland's 32 local government council areas. The council area includes urban Edinburgh and a rural area...

, Scotland, and also at Perth
Perth Observatory
The Perth Observatory is the name of two astronomical observatories located in Western Australia.-First Perth Observatory:The original Perth Observatory was constructed in 1896 and was officially opened in 1900 by John Forrest, the first premier of Western Australia. The observatory was located at...

 in Australia 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, Chile
Santiago, Chile
Santiago , also known as Santiago de Chile, is the capital and largest city of Chile, and the center of its largest conurbation . It is located in the country's central valley, at an elevation of above mean sea level...

, is shot every noon. In places where a cannon is used for a time signal, locals often joke that they can spot tourists because they jump in surprise while locals check their watches. In many Midwestern US cities where tornadoes
are a common hazard, the emergency sirens are tested regularly at a specified
time (such as, say, noon each Saturday); while this is not primarily intended
as a time signal, locals often do check their watches when they hear it.

The first time ball
Time ball
A time ball is a large painted wooden or metal ball that drops at a predetermined time, principally to enable sailors to check their marine chronometers from their boats offshore...

 was erected at Portsmouth
Portsmouth
Portsmouth is the second largest city in the ceremonial county of Hampshire on the south coast of England. Portsmouth is notable for being the United Kingdom's only island city; it is located mainly on Portsea Island...

, England in 1829 by its inventor Robert Wauchope. One was installed in 1833 on the roof of the Royal Observatory in Greenwich
Greenwich
Greenwich is a district of south London, England, located in the London Borough of Greenwich.Greenwich is best known for its maritime history and for giving its name to the Greenwich Meridian and Greenwich Mean Time...

, London, and the time ball has dropped at 1pm every day since then. The first American time ball went into service in 1845. Because the speed of light
Speed of light
The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...

 is much faster than the speed of sound
Speed of sound
The speed of sound is the distance travelled during a unit of time by a sound wave propagating through an elastic medium. In dry air at , the speed of sound is . This is , or about one kilometer in three seconds or approximately one mile in five seconds....

, visible signals enabled greater precision than audible ones; however, the audible signals could operate under conditions of reduced visibility. In 1861 and 1862, the Post Office Directory had time gun map
Map
A map is a visual representation of an area—a symbolic depiction highlighting relationships between elements of that space such as objects, regions, and themes....

s published that related the number of seconds it took for the report of the time gun to reach various locations in Edinburgh. The ceremony of Times Square Ball
Times Square Ball
The Times Square Ball is a time ball dropped each year during the New Year’s Eve celebration in Times Square, Manhattan, New York City. The ball is made by Waterford Crystal and electric lights is raised to the top of a pole on the One Times Square building at 6:00 pm and then lowered to mark the...

 drop at New Year's Eve in Times Square
Times Square
Times Square is a major commercial intersection in the borough of Manhattan in New York City, at the junction of Broadway and Seventh Avenue and stretching from West 42nd to West 47th Streets...

, New York City, is a vestige of a visual indication of time.

In many non-seafaring communities, loud factory whistle
Whistle
A whistle or call is a simple aerophone, an instrument which produces sound from a stream of forced air. It may be mouth-operated, or powered by air pressure, steam, or other means...

s served as public time signals before radio made them obsolete.

Electrical time signals


Sandford Fleming
Sandford Fleming
Sir Sandford Fleming, was a Scottish-born Canadian engineer and inventor, proposed worldwide standard time zones, designed Canada's first postage stamp, a huge body of surveying and map making, engineering much of the Intercolonial Railway and the Canadian Pacific Railway, and was a founding...

 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 anti-meridian of Greenwich (now 180°). He suggested that standard time zone
Time zone
A time zone is a region on Earth that has a uniform standard time for legal, commercial, and social purposes. In order for the same clock time to always correspond to the same portion of the day as the Earth rotates , different places on the Earth need to have different clock times...

s could be used locally, but they were subordinate to his single world time.

Standard time
Standard time
Standard time is the result of synchronizing clocks in different geographical locations within a time zone to the same time rather than using the local meridian as in local mean time or solar time. Historically, this helped in the process of weather forecasting and train travel. The concept...

 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
American Railway Association
The American Railway Association was an industry trade group representing railroads in the United States. The organization had its inception in meetings of General Managers and ranking railroad operating officials known as Time Table Conventions, the first of which was held on October 1, 1872, at...

, approved a plan that divided the United States into several time zone
Time zone
A time zone is a region on Earth that has a uniform standard time for legal, commercial, and social purposes. In order for the same clock time to always correspond to the same portion of the day as the Earth rotates , different places on the Earth need to have different clock times...

s. On that November day, the United States Naval Observatory
United States Naval Observatory
The United States Naval Observatory is one of the oldest scientific agencies in the United States, with a primary mission to produce Positioning, Navigation, and Timing for the U.S. Navy and the U.S. Department of Defense...

 telegraphed a signal that coordinated noon at Eastern standard time with 11 am Central, 10 am Mountain, and 9 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.

Radio time sources



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
Network Time Protocol
The Network Time Protocol is a protocol and software implementation for synchronizing the clocks of computer systems over packet-switched, variable-latency data networks. Originally designed by David L...

 servers
Server (computing)
In the context of client-server architecture, a server is a computer program running to serve the requests of other programs, the "clients". Thus, the "server" performs some computational task on behalf of "clients"...

 as well as atomic clock
Atomic clock
An atomic clock is a clock that uses an electronic transition frequency in the microwave, optical, or ultraviolet region of the electromagnetic spectrum of atoms as a frequency standard for its timekeeping element...

s in GPS satellites. Since 1905 time signals have been transmitted by radio. There are dedicated radio time signal stations around the world.

Time stations operating in the longwave
Longwave
In radio, longwave refers to parts of radio spectrum with relatively long wavelengths. The term is a historic one dating from the early 20th century, when the radio spectrum was considered to consist of long, medium and short wavelengths...

 radio band have highly predictable radio propagation
Radio propagation
Radio propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere...

 characteristics, which gives low uncertainty in the received time signals. Stations operating in the shortwave
Shortwave
Shortwave radio refers to the upper MF and all of the HF portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used...

 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.

Radio time signal stations broadcast the time in both audible and machine readable time code
Time code
A timecode is a sequence of numeric codes generated at regular intervals by a timing system.- Video and film timecode :...

 form that can be used as references for radio clock
Radio clock
A radio clock or radio-controlled clock is a clock that is synchronized by a time code bit stream transmitted by a radio transmitter connected to a time standard such as an atomic clock...

s and radio-controlled watches.
The audio portions of the WWV and WWVH broadcasts can also be heard by telephone. The time announcements are normally delayed by less than 30 ms when using land lines from within the continental United States, and the stability (delay variation) is generally < 1 ms. When mobile phones are used, the delays are often more than 100 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 to 500 ms.
To hear these broadcasts, dial (303) 499-7111 for WWV (Colorado), and (808) 335-4363 for WWVH (Hawaii). Callers are disconnected after 2 minutes. These are not toll-free numbers; callers outside the local calling area are charged for the call at regular long distance rates.
Loran-C time signals may also be 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.

Commercial broadcasts


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 included time "pips" in its broadcasts from 1922.

In the United States, many information-based radio stations (full-service, all-news and news/talk) also broadcast time signals at the top of the hour. In New York, WCBS
WCBS (AM)
WCBS , often referred to as "WCBS Newsradio 880" , is a radio station in New York City. Owned by CBS Radio, the station broadcasts on a clear channel and is the flagship station of the CBS Radio Network...

 and WINS
WINS (AM)
WINS , known on-air as "Ten-Ten Wins", is a radio station in New York City, owned by CBS Radio. WINS's studios are in the combined CBS Radio facility at 345 Hudson Street in the TriBeCa section of Manhattan, and transmitting towers in Lyndhurst, New Jersey.WINS is one of the nation's oldest...

, as well as WBEN
WBEN (AM)
WBEN is an AM and FM radio station serving the Niagara, Buffalo and Western New York area, broadcasting on 930 AM and, as of April 5, 2011, simulcasting on sister station WLKK at 107.7 FM. It previously simulcasted between 1946 and 1960 on 102.5 FM as WBEN-FM. Both stations retained the WBEN...

 in Buffalo, New York
Buffalo, New York
Buffalo is the second most populous city in the state of New York, after New York City. Located in Western New York on the eastern shores of Lake Erie and at the head of the Niagara River across from Fort Erie, Ontario, Buffalo is the seat of Erie County and the principal city of the...

, have distinctive top-of-the-hour tones, though the WINS signal is only approximate (several seconds error) . WINS and WBEN also has a tone at 30 minutes past the hour for those setting their clocks. Vancouver
Vancouver
Vancouver is a coastal seaport city on the mainland of British Columbia, Canada. It is the hub of Greater Vancouver, which, with over 2.3 million residents, is the third most populous metropolitan area in the country,...

 radio station CKNW also broadcasts time signals, using a chime every half-hour.

Stations using iBiquity Digital Corporation's "HD Radio
HD Radio
HD Radio, which originally stood for "Hybrid Digital", is the trademark for iBiquity's in-band on-channel digital radio technology used by AM and FM radio stations to transmit audio and data via a digital signal in conjunction with their analog signals...

" system are contractually required 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. Local signals may also be delayed.

The all-news radio
All-news radio
All-news radio is a radio format devoted entirely to discussion and broadcast of news.All-news radio is available in both local and syndicated forms, and is carried in some form on both major US satellite radio networks...

 stations of the CBS Radio Network
CBS Radio Network
The CBS Radio Network provides news, sports and other programming to more than 1,000 radio stations throughout the United States. The network is owned by CBS Corporation, and operated by CBS Radio ....

, of which WCBS is the flagship, air a "bong" (sounding A=440 Hz [piano note]) that immediately precedes each top-of-the-hour network newscast. (The same bong could be heard on the CBS
CBS
CBS Broadcasting Inc. is a major US commercial broadcasting television network, which started as a radio network. The name is derived from the initials of the network's former name, Columbia Broadcasting System. The network is sometimes referred to as the "Eye Network" in reference to the shape of...

 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
KNX (AM)
KNX is an all-news radio station in Los Angeles, California, USA. The station operates on a clear channel and is owned by CBS Radio. KNX broadcasts from facilities shared with sister stations KFWB, KCBS-FM, KTWV, and KAMP on Los Angeles' Miracle Mile...

, 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 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).

In Canada, the national non-commercial CBC Radio
Canadian Broadcasting Corporation
The Canadian Broadcasting Corporation, commonly known as CBC and officially as CBC/Radio-Canada, is a Canadian crown corporation that serves as the national public radio and television broadcaster...

 network broadcasts the daily National Research Council Time Signal
National Research Council Time Signal
The National Research Council Time Signal is Canada's longest running but shortest radio programme. Heard every day since November 5, 1939 , shortly before 13:00 Eastern Time across the CBC Radio One network, it lasts between 15 and 45 seconds, ending exactly at 13:00...

 at local noon on the Radio 1 network.

In Australia, many information-based radio stations broadcast time signals at the top of the hour and a speaking clock service is also available. However, the former VNG dedicated time signal service has been discontinued.

See also

  • American Practical Navigator
  • Atomic clock
    Atomic clock
    An atomic clock is a clock that uses an electronic transition frequency in the microwave, optical, or ultraviolet region of the electromagnetic spectrum of atoms as a frequency standard for its timekeeping element...

  • Car radio
    Car radio
    Car radio may refer to:*a radio in a car. See car audio and in car entertainment*"Car Radio", a song by Spoon from their 1998 album A Series of Sneaks...

    , Radio Data System
    Radio Data System
    Radio Data System, or RDS, is a communications protocol standard for embedding small amounts of digital information in conventional FM radio broadcasts. RDS standardises several types of information transmitted, including time, station identification and programme information.Radio Broadcast Data...

     (RDS)
  • Comparison of time signal radio stations
  • Extended Data Services
    Extended Data Services
    Extended Data Services , is an American standard classified under Electronic Industries Alliance standard CEA-608-E for the delivery of any ancillary data to be sent with an analog television program, or any other NTSC video signal.XDS is used by TV stations, TV networks, and TV program...

     and PBS
  • Global Positioning System#Timekeeping
  • Greenwich Time Signal
    Greenwich Time Signal
    The Greenwich Time Signal , popularly known as the pips, is a series of six short tones broadcast at one-second intervals by many BBC Radio stations to mark the precise start of each hour...

  • Low frequency
    Low frequency
    Low frequency or low freq or LF refers to radio frequencies in the range of 30 kHz–300 kHz. In Europe, and parts of Northern Africa and of Asia, part of the LF spectrum is used for AM broadcasting as the longwave band. In the western hemisphere, its main use is for aircraft beacon,...

    , (LF)
  • Marine chronometer
    Marine chronometer
    A marine chronometer is a clock that is precise and accurate enough to be used as a portable time standard; it can therefore be used to determine longitude by means of celestial navigation...

  • Network time protocol
    Network Time Protocol
    The Network Time Protocol is a protocol and software implementation for synchronizing the clocks of computer systems over packet-switched, variable-latency data networks. Originally designed by David L...

  • Radio clock
    Radio clock
    A radio clock or radio-controlled clock is a clock that is synchronized by a time code bit stream transmitted by a radio transmitter connected to a time standard such as an atomic clock...

  • Radio VNG - Australia
  • Radio-controlled watch
  • Smart Personal Objects Technology
    Smart Personal Objects Technology
    Smart Personal Object Technology was developed by Microsoft to personalize household electronics and other everyday devices, through "smart" software and hardware that would make their uses more versatile....

    , (SPOT)
  • Speaking clock
    Speaking clock
    A speaking clock service is a recorded or simulated human voice service, usually accessed by telephone, that gives the correct time. The first telephone speaking clock service was introduced in France, in association with the Paris Observatory on 14 February 1933.The format of the service is...

  • Synchronization
    Synchronization
    Synchronization is timekeeping which requires the coordination of events to operate a system in unison. The familiar conductor of an orchestra serves to keep the orchestra in time....

  • Time transfer
    Time transfer
    Time transfer is a scheme where multiple sites share a precise reference time. Time transfer solves problems such as astronomical observatories correlating observed flashes or other phenomenon with each other, as well as cell phone towers coordinating handoffs as a phone moves from one cell to...

  • VBI, VITC, Time code
    Time code
    A timecode is a sequence of numeric codes generated at regular intervals by a timing system.- Video and film timecode :...

  • Watch
    Watch
    A watch is a small timepiece, typically worn either on the wrist or attached on a chain and carried in a pocket, with wristwatches being the most common type of watch used today. They evolved in the 17th century from spring powered clocks, which appeared in the 15th century. The first watches were...


External links