It (also called an e-stop) is a security measure used to shut off a device in an emergency situation in which it cannot be shut down in the usual manner.
Unlike a normal shut down, which shuts down all systems naturally and turns the machine off without damaging it, a kill switch is designed to completely abort the operation at all costs.
Often, they are used to protect people from sustaining an injury or being killed, in which case damaging the machine may be considered to be acceptable.
A similar system, usually called a dead man's switch (A dead man's switch [for other names, see alternative names], as its name suggests, is a device intended to stop a machine in case the human operator becomes incapacitated, and is a form of fail-safe.
They are commonly used in locomotives, freight elevators, lawn mowers, tractors, jet skis, outboard motors, snowblowers and snowmobiles.
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