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 and/or switch:
“The five kings count the dead but do not soften
The crusted wound nor stroke the brow;
A hand rules pity as a hand rules heaven;
Hands have no tears to flow.”
—Dylan Thomas (1914–1953)
“A man is a beggar who only lives to the useful, and, however he may serve as a pin or rivet in the social machine, cannot be said to have arrived at self-possession.”
—Ralph Waldo Emerson (1803–1882)
“Children ... after a certain age do not welcome parental advice. Occasionally, they may listen to another adult, which is why perhaps people should switch children with their neighbors and friends for a while in the teen years!”
—Marian Wright Edelman (20th century)