Question: When did the Paris Observatory use the Eiffel Tower as an antenna to communication with the US Naval Observatory in Arlington, VA?
About the article "Eiffel Tower", section "Communications".

Candidate passages:
The tower has been used for radio transmission since the beginning of the 20th century.
Until the 1950s, sets of antenna wires ran from the summit to anchors on the Avenue de Suffren and Champ de Mars.
These were connected to long-wave transmitters in small bunkers; in 1909 a permanent underground radio centre was built near the south pillar, which still exists today.
On 20 November 1913 the Paris Observatory, using the Eiffel Tower as an antenna, exchanged sustained wireless signals with the United States Naval Observatory which used an antenna in Arlington, Virginia.
The object of the transmissions was to measure the difference in longitude between Paris and Washington, D.C. Today, both radio and television stations broadcast their signals from the top of the Eiffel Tower.
Its foundation lies in the ambitions of Jean-Baptiste Colbert to extend France's maritime power and international trade in the 17th century.
Louis XIV promoted its construction starting in 1667, being completed in 1671.
It thus predates by a few years the Royal Greenwich Observatory in England, which was founded in 1675.
The architect of the Paris Observatory was Claude Perrault whose brother, Charles, was secretary to Colbert and superintendent of public works.
Optical instruments were supplied by Giuseppe Campani.
The buildings were extended in 1730, 1810, 1834, 1850, and 1951.
The last extension incorporates the spectacular Meridian Room designed by Jean Prouvé.
The world's first national almanac, the "Connaissance des temps" was published by the observatory in 1679, using eclipses in Jupiter's satellites to aid sea-farers in establishing longitude.
In 1863, the observatory published the first modern weather maps.
In 1882, a astrographic lens was constructed, an instrument that catalysed what proved to be the over-ambitious, international "Carte du Ciel" project.
In November 1913, the Paris Observatory, using the Eiffel Tower as an antenna, exchanged sustained wireless (radio) signals with the United States Naval Observatory to determine the exact difference of longitude between the two institutions. 
Established by the order of the Secretary of the Navy John Branch on 6 December 1830 as the Depot of Charts and Instruments, the Observatory rose from humble beginnings.
Placed under the command of Lieutenant Louis M. Goldsborough, with an annual budget of $330, its primary function was the restoration, repair, and rating of navigational instruments.
It was made into a national observatory in 1842 via a federal law and a Congressional appropriation of $25,000.
Lieutenant James Melville Gilliss was put in charge of "obtaining the instruments needed and books."
Lt. Gilliss visited the principal observatories of Europe with the mission to purchase telescopes and scientific devices and books.
The observatory's primary mission was to care for the United States Navy's marine chronometers, charts, and other navigational equipment.
It calibrated ships' chronometers by timing the transit of stars across the meridian.
Initially located downtown at in Foggy Bottom (near the Lincoln Memorial), the observatory moved in 1893 to its present location on a 2000-foot circle of land atop Observatory Hill overlooking Massachusetts Avenue.
The first superintendent was Navy Commander Matthew Fontaine Maury.
Maury had the world's first vulcanized time ball, created to his specifications by Charles Goodyear for the U.S. Observatory.
It was the first time ball in the United States, being placed into service in 1845, and the 12th in the world.
Maury kept accurate time by the stars and planets.
The time ball was dropped every day except Sunday precisely at the astronomically defined moment of Mean Solar Noon, enabling all ships and civilians to know the exact time.
By the end of the American Civil War, the Observatory's clocks were linked via telegraph to ring the alarm bells in all of the Washington, D.C. firehouses three times a day, and by the early 1870s the Observatory's daily noon time signal was being distributed nationwide via the Western Union Telegraph Company.
Time was also "sold" to the railroads and was used in conjunction with railroad chronometers to schedule American rail transport.
Early in the 20th century, the Arlington Time Signal broadcast this service to wireless receivers.
The names "National Observatory" and "Naval Observatory" were both used for 10 years, until a ruling was passed to officially use the latter.
The precedent to have been ascribed the title 'national observatory' can in part be attributed to the efforts of John Quincy Adams during that period, who made protracted efforts to bring astronomy to a national level at that time.
In 1849 the Nautical Almanac Office (NAO) was established in Cambridge, Massachusetts as a separate organization.
It was moved to Washington, D. C. in 1866, colocating with the U. S. Naval Observatory in 1893.
On September 20, 1894, the NAO became a "branch" of USNO, however it remained autonomous for several years after this.
President John Quincy Adams, who in 1825 signed the bill for the creation of a national observatory just before leaving presidential office, had intended for it to be called the National Observatory.
He spent many nights at the observatory with Maury, watching and charting the stars, which had always been one of Adams' avocations.
An early scientific duty assigned to the Observatory was the U.S. contribution to the definition of the Astronomical Unit, or the AU, which defines a standard mean distance between the Sun and the Earth, conducted under the auspices of the Congressionally funded U.S.
Transit of Venus Commission.
The astronomical measurements taken of the transit of Venus by a number of countries since 1639 resulted in a progressively more accurate definition of the AU.
Relying heavily on photographic methods, the naval observers returned 350 photographic plates in 1874, and 1,380 measurable plates in 1882.
The results of the surveys conducted simultaneously from several locations around the world (for each of the two transits) produced a final value of the solar parallax, after adjustments, of 8.809", with a probable error of 0.0059", yielding a "U.S. defined" Earth-Sun distance of , with a probable error of miles.
This calculated distance was a significant improvement over several previous estimates.
The telescope used for the discovery of the Moons of Mars was the 26-inch (66 cm) refractor (a telescope with a lens), then located at Foggy Bottom.
In 1893 it was moved to the present location, into the 21st century.
In November 1913 the Paris Observatory, using the Eiffel Tower as an antenna, exchanged sustained wireless (radio) signals with the United States Naval Observatory, using an antenna in Arlington, Virginia to determine the exact difference of longitude between the two institutions.
In 1934, the last large telescope to be installed at USNO saw "first light".
This 40-inch aperture instrument was also the second (and final) telescope made by famed optician, George Ritchey.
The Ritchey-Chrétien telescope design has since become the defacto optical design for nearly all major telescopes, including the famed Keck telescopes and the spaceborne Hubble Telescope.
Unfortunately, light pollution forced USNO to think of other more viable locations to continue work, and so began a search.
The final dark sky site chosen was Flagstaff, Arizona, and so the 40-inch telescope was moved to that location, beginning operations at the new Navy command, now called the Naval Observatory Flagstaff Station (NOFS).
Those operations commenced in 1955, and within a decade, the Navy's largest telescope, the 61-inch "Kaj Strand Astrometric Reflector" was built, seeing light at NOFS in 1964.
The modern United States Naval Observatory continues to be a major authority in the areas of precise time and time interval, Earth orientation, astrometry and celestial observation.
In collaboration with many national and international scientific establishments, it determines the timing and astronomical data required for accurate navigation, astrometry, and fundamental astronomy and calculation methods—and distributes this information (such as astronomical catalogs) in the Astronomical Almanac, the Nautical Almanac, and on-line.
Perhaps it is best known to the general public for its highly accurate ensemble of atomic clocks and its year 2000 Timeball replacement.
The site also houses the largest astronomy library in the United States (and the largest astrophysical periodicals collection in the world).
The library includes a large collection of rare, often famous, physics and astronomy books from across the past millennium.USNO continues to maintain its dark-sky observatory, NOFS, near Flagstaff, Arizona, which also now oversees the Navy Precision Optical Interferometer.
NOFS opens to the public one weekend annually, in the autumn.
The Alternate Master Clock, mentioned above, also continues to operate at Schriever AFB in Colorado. 
1811: Tartu Old Observatory, Estonia 1830/1842: Depot of Charts & Instruments/US Naval Observatory, USA 1830: Yale University Observatory Atheneum, USA 1836: Hopkins Observatory, Williams College, USA 1839: Pulkovo Observatory, Russia 1839/1847: Harvard College Observatory, USA 1842: Cincinnati Observatory, USA 1873: Quito Astronomical Observatory, Ecuador 1884: McCormick Observatory, USA 1890: Smithsonian Astrophysical Observatory, USA 1894: Lowell Observatory, USA  
Burrell Memorial Observatory referred to as Burrell Observatory is an astronomical observatory located on the campus of Baldwin Wallace University.
The observatory was established in 1940, in Berea, Ohio.