A dead man's switch (for other names, see alternative names) is a switch that is automatically operated in case the human operator becomes incapacitated, such as through death or loss of consciousness.
The switch, a form of fail-safe, is usually wired so that it stops a machine by breaking a series circuit, although a spring-operated "dead man's switch" can be used to activate a system by completing a circuit when it is no longer held down (as in some explosive vests detonated by suicide bombers). Switches of the former type are commonly used in locomotives, aircraft refuelling, freight elevators, lawn mowers, tractors, personal watercraft, outboard motors, chainsaws, snowblowers, tread machines, snowmobiles, and many medical imaging devices.
A dead man's switch may also be used to activate a harmful device, such as a bomb or IED. The user holds down a switch of some sort in their hand which arms the device. When the switch is released, the device will activate, so that if the user is killed while holding the switch, the switch will be released and the bomb will detonate (i.e. fail-deadly). The Special Weapons Emergency Separation System is an application of this concept in the field of nuclear weapons (see Dead Hand (nuclear war)).
A similar concept has been employed with computer data, where the "switch" is a decryption key that can release sensitive information, as with the WikiLeaks "Insurance File".
Read more about Dead Man's Switch: Background, Vigilance Control, Alternative Names, Event Recording
Famous quotes containing the words dead man, dead, man and/or switch:
“Wild Bill was indulging in his favorite pastime of a friendly game of cards in the old No. 10 saloon. For the second time in his career, he was sitting with his back to an open door. Jack McCall walked in, shot him through the back of the head, and rushed from the place, only to be captured shortly afterward. Wild Bill’s dead hand held aces and eights, and from that time on this has been known in the West as “the dead man’s hand.””
—State of South Dakota, U.S. public relief program (1935-1943)
“an endless wind
Whips at the headstones of the dead and wails
In the trees for all who have and have not sinned.”
—Anthony Hecht (b. 1923)
“Criticism is a study by which men grow important and formidable at very small expense. The power of invention has been conferred by nature upon few, and the labour of learning those sciences which may, by mere labour, be obtained, is too great to be willingly endured; but every man can exert some judgment as he has upon the works of others; and he whom nature has made weak, and idleness keeps ignorant, may yet support his vanity by the name of critic.”
—Samuel Johnson (1709–1784)
“Uncritical semantics is the myth of a museum in which the exhibits are meanings and the words are labels. To switch languages is to change the labels.”
—Willard Van Orman Quine (b. 1908)