Historical
The world's first IFF, FuG 25a "Erstling" (English: "Debut"), was developed in Germany in 1940. It received the radar frequencies on 125 MHz (Freya radar) and 550-580 MHz (Würzburg radar). To start the identification procedure, the ground operator switched the pulse frequency of his radar from 3,750 Hz to 5,000 Hz.
The airborne receiver decoded that and started to transmit its code. Before departure, two mechanical keys of ten bits each were inserted into the shown reader. The IFF transmitter worked on 168 MHz with a power of 400 Watt (PEP). Unfortunately for the Germans, British military scientists designed and built their own IFF transmitter called "Perfectos", which was designed to trigger a response from any FuG 25a systems in the vicinity. When mounted in an RAF Mosquito, the "Perfectos" device revealed the position of any German nightfighters fitted with an FuG 25a. As a result, the British "Perfectos" device severely compromised German use of the FuG 25a.
Read more about this topic: Identification Friend Or Foe
Famous quotes containing the word historical:
“Some minds are as little logical or argumentative as nature; they can offer no reason or “guess,” but they exhibit the solemn and incontrovertible fact. If a historical question arises, they cause the tombs to be opened. Their silent and practical logic convinces the reason and the understanding at the same time. Of such sort is always the only pertinent question and the only satisfactory reply.”
—Henry David Thoreau (1817–1862)
“By contrast with history, evolution is an unconscious process. Another, and perhaps a better way of putting it would be to say that evolution is a natural process, history a human one.... Insofar as we treat man as a part of nature—for instance in a biological survey of evolution—we are precisely not treating him as a historical being. As a historically developing being, he is set over against nature, both as a knower and as a doer.”
—Owen Barfield (b. 1898)
“Quite apart from any conscious program, the great cultural historians have always been historical morphologists: seekers after the forms of life, thought, custom, knowledge, art.”
—Johan Huizinga (1872–1945)