What is a Kill Switch?

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  • Written By: Malcolm Tatum
  • Edited By: Bronwyn Harris
  • Last Modified Date: 20 November 2019
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Also known as a dead man’s switch, an emergency stop, or an e-stop, a kill switch is a device that makes it possible to shut down machinery or equipment when the typical shut-down applications fail to respond. Used only for severe situations, this type of safety switch immediately terminates or kills the power supply to the machinery, rather than following the gradual powering down process that is normally followed during a controlled shutdown. The switch bypasses protocols designed to prevent damage to the machinery, usually in order to save time and increase the chances of avoiding injury or death of people who are in the immediate area.

The exact configuration of the kill switch will depend on the type of machinery or equipment involved. Some are designed to automatically activate in the event that the operator is incapacitated for some reason and is no longer able to control the function of the device. Usually referred to as a dead man’s switch, this particular application is often found with tractors, freight elevators, lawn mowers, and other machinery that requires ongoing manipulation by an operator in order to engage in a task. Even with pleasure boats, this type of kill switch may be used, often by connecting the switch to a rope on the operator’s life jacket. In the event that the operator is incapacitated or even thrown overboard, the pull on the cord toggles the switch and the outboard motor is deactivated.


It is not unusual for production facilities to also incorporate the idea of a kill switch into each machine used in the process. Here, the switch may be structured to initiate when an operator is no longer actively managing a task, or may be a manual switch that can quickly be activated in the event of an emergency. For example, if an operator should suddenly lose consciousness and be in danger of falling into a piece of moving machinery, throwing the kill switch stops the machine’s motion and decreases the chances of a serious injury to the operator.

In some cases, the kill switch is triggered when power surges or some impending failure of a machine component is detected by a computer system monitoring the operation. Here, the system is programmed to identify changes in power flow or irregularities in the performance of the machinery. When something outside a certain range of operation is identified, the system activates the kill switch and alerts maintenance and repair personnel of the problem. Doing so helps to prevent the potential for electrical shock from the power surges while also preventing a machine malfunction that could also result in injury to an operator.


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