IFF Mark II was the first operational identification friend or foe
system, developed by the Royal Air Force just before World War II. The
Mark I, its predecessor, amplified the signals of the British Chain
Home radar systems, triggering a radar display blip. It required manual
tuning, and operators could not always distinguish between an enemy
aircraft and a friendly one with a maladjusted IFF. The Mark II,
deployed at the end of the Battle of Britain in late 1940, fixed this
problem with an automatic gain control and three automatic tuners that
covered a wider selection of radars. The Mark II's frequencies were
sufficient for the early war period, but by 1942 many more radars were
in use, including incompatible ones based on the cavity magnetron. The
IFF Mark III eliminated the multiple tuners and operated on a single
frequency that could be used with any radar; it entered service in 1943
and quickly replaced the Mark II.
Read more: <https://en.wikipedia.org/wiki/IFF_Mark_II>
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Today's selected anniversaries:
1551:
Sue Takafusa, a military leader for the Ōuchi clan in western
Japan, led a coup against the daimyō, Ōuchi Yoshitaka, leading to the
latter's forced suicide.
<https://en.wikipedia.org/wiki/Tainei-ji_incident>
1882:
The Vulcan Street Plant, the first hydroelectric central
station to serve a system of private and commercial customers in North
America, went on line in Appleton, Wisconsin.
<https://en.wikipedia.org/wiki/Vulcan_Street_Plant>
1939:
NBC broadcast the first televised American football game,
between the Fordham Rams and the Waynesburg Yellow Jackets.
<https://en.wikipedia.org/wiki/1939_Waynesburg_vs._Fordham_football_game>
2009:
A 7.6 MW earthquake struck off the southern coast of Sumatra,
Indonesia (damage pictured), killing 1,115 and impacting an estimated
1.2 million people.
<https://en.wikipedia.org/wiki/2009_Sumatra_earthquakes>
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Wiktionary's word of the day:
Plutonian:
1. (Greek mythology, Roman mythology) Of or relating to Pluto, the Greek
and Roman god of the underworld; demonic, infernal.
2. (by extension) Of, relating to, or having characteristics associated
with the underworld; dark, gloomy; mournful.
3. (by extension, geology) Synonym of plutonic (“of or pertaining to
rocks formed deep in the Earth's crust, rather than by volcanoes at the
surface of the Earth”)
4. (by extension, geology, historical) Synonym of plutonic (“of,
pertaining to, or supporting plutonism, the theory that the rocks of the
Earth were formed in fire by volcanic activity, with a continuing
gradual process of weathering and erosion, then deposited on the sea
bed, re-formed into layers of sedimentary rock by heat and pressure, and
raised again”) [...]
5. (astrology) Pertaining to the astrological influence of Pluto,
formerly regarded as a planet.
6. (astronomy) Of or relating to the dwarf planet Pluto.
<https://en.wiktionary.org/wiki/Plutonian>
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Wikiquote quote of the day:
Silence is an ocean. Speech is a river. When the ocean is
searching for you, don't walk into the language-river. Listen to the
ocean, and bring your talky business to an end Traditional words are
just babbling in that presence, and babbling is a substitute for
sight.
--Rumi
<https://en.wikiquote.org/wiki/Rumi>