View source for Kill switch

{{short description|Safety mechanism to quickly shut down a system}}
{{use American English|date=January 2023}}
{{use mdy dates|date=January 2023}}
{{about|the safety mechanism|other uses|Kill switch (disambiguation)}}
{{redirect|Emergency stop|when trains make an emergency stop|Emergency brake (train)}}
{{Infobox machine
| name           = Kill switch
| image          = Not-Aus Betätiger.jpg
| caption        = A kill switch without a cover
| classification = Mechanical component
| industry       = Automotive, boating, energy, engineering, entertainment
| application    =
| dimensions     =
| weight         =
| fuel_source    =
| powered        = Varies, some mechanical
| self-propelled =
| wheels         =
| tracks         =
| legs           =
| aerofoils      =
| axles          =
| components     =
| invented       =
| inventor       =
| examples       =
}}
A '''kill switch''', also known more formally as an '''emergency brake''', '''emergency stop''' ('''E-stop'''), '''emergency off''' ('''EMO'''), or '''emergency power off''' ('''EPO'''), is a [[safety]] mechanism used to shut off [[Machine|machinery]] in an [[emergency]], when it cannot be shut down in the usual manner.  Unlike a normal shut-down [[switch]] or shut-down procedure, which shuts down all systems in order and turns off the machine without damage, a kill switch is designed and configured to abort the operation as quickly as possible (even if it damages the equipment) and to be operated simply and quickly (so that even a [[panic]]ked operator with impaired [[executive functions]] or a bystander can activate it). Kill switches are usually designed to be noticeable, even to an untrained operator or a bystander.

Some kill switches feature a removable, protective barrier against accidental activation (e.g. a [[plastic]] cover that must be lifted or [[glass]] that must be broken), known as a[[wiktionary:molly-guard| mollyguard]]. Kill switches are features of mechanisms whose normal operation or foreseeable misuse might cause [[injury]] or [[death]]; industrial designers include kill switches because damage to or the destruction of the machinery is less important than preventing workplace injuries and deaths.

A similar system, usually called a [[dead man's switch]], is a device intended to stop a machine (or activate one) if the human operator becomes incapacitated or leaves the machine unattended, and is a form of [[fail-safe]]. They are commonly used in industrial applications (e.g., [[locomotive]]s, [[tower cranes]], [[freight elevator]]s) and consumer applications (e.g., [[lawn mower]]s, [[Tractor|tractors]], [[personal watercraft]], [[Outboard motor|outboard motors]], [[snow blower]]s, [[motorcycle]]s and [[snowmobile]]s). The switch in these cases is held by the user, and turns off the machine if they let go. Some riding lawnmowers have a kill switch in the seat which stops the engine and blade if the operator's weight is no longer on the seat.

==Vehicles==
[[Image:Emergency Train Stop Button.jpg|right|thumb|An emergency switch in Japan]]
On [[rail transport|railways]],<ref>{{cite news |newspaper=[[BizJournals]].com (Pittsburgh)
   |url=https://www.bizjournals.com/pittsburgh/news/2017/12/21/many-trains-still-lack-crucial-braking-system.html
   |title=Law Requires Life-Saving Braking Device: Most Trains Still Lack Crucial Braking System
   |author=Patrick McGeehan |date=December 20, 2017}}</ref> an emergency stop is a full application of the [[emergency brake (train)|brakes]] in order to bring a [[train]] to a stop as quickly as possible.<ref>{{cite news |newspaper=[[The Los Angeles Times]]  |url=https://www.latimes.com/nation/la-na-new-york-train-crash-ntsb-20150205-story.html
|title=Train engineer pulled emergency brake when he saw SUV |date=February 5, 2015}}</ref> This occurs either by a manual emergency stop activation, such as a button being pushed on the train to start the emergency stop, or on some trains automatically, when the train has [[signal passed at danger|passed a red signal]] or the driver has failed to respond to warnings to check that they are still alert, which is known as a [[dead man's switch]]. A similar mechanism is the [[watchdog timer]].

In large [[Ship|ships]], an emergency stop button pulls the [[countershaft]] for the [[Fuel pump|fuel pumps]] to the stop position, cutting off the fuel supply and stopping the engines. With a [[Controllable pitch propeller|controllable-pitch propeller]], the stop button may declutch the engine from the propeller.

[[NASCAR]] requires all their stock cars to be equipped with a [[steering wheel]]–mounted kill switch, in case the [[accelerator pedal]] sticks and the driver needs to shut down the engine.

A related concept is the [[dead man's switch]], where the operator must be holding a button or lever any time the vehicle is operating.  A common example of this is the kill switches used by [[boat]]ers and [[jetski]]ers wherein a cord connects the kill switch to the operator (usually by the operator's [[personal flotation device|life jacket]] or clothing), and if the operator is thrown overboard in an accident, the cord will pull the switch and immediately shut down the vessel's engine. This prevents it from becoming a runaway vessel that could impose a danger to other vessels or swimmers at sea, and allows the operator to swim back to the vessel and re-board it without the risk of being injured by the boat's propeller.  A similar device is featured on most lawnmowers: a lever on the handle either disables the ignition system and applies a brake to the [[flywheel]] (on a gasoline lawnmower), or cuts the power to the motor (on an electric lawnmower), as long as it is not held down.

Monster Truck Racing Association requires all of their [[monster trucks]] to be equipped with kill switches (either remote or in cab), in case the monster truck loses control and the driver needs to shut off the engine. Monster trucks' kill switches are tested before races. {{citation needed|date=December 2015}}

===Pioneer-era planes and World War I aircraft===
Early aviators using [[rotary engine]]–powered aircraft from [[Aviation in the pioneer era|the beginnings of their use]] [[Gnome Omega|in 1908]], up through the end of [[Aviation in World War I|World War I]] in 1918 had what could be called a reversed functionality version of the "dead man's switch" for cutting the [[spark ignition|ignition]] voltage to the spark plugs on such a power-plant, to give a degree of in-flight speed control for a rotary engine.  This was often called [[Rotary engine#Rotary engine control|a "blip switch" or "coupe switch"]] (from the French term {{Lang|fr|coupez}}, or "cut") and when not being pressed, allowed the high voltage from the engine's [[ignition magneto|magnetos]] to operate the ignition with normal engine operation in flight—pressing the "blip switch" cut the flow of high voltage from the magnetos, stopping the combustion process in the cylinders. When such a "blip switch" was intermittently used on landing approach, this allowed a limited degree of engine speed control, as rotary engines generally did not have a conventional [[throttle]] in their [[carburetor|carburettors]] to regulate engine speed, but only for governing the fuel-air ratio for start-up and full-speed operation.

==Anti-theft==
Kill switches are also used on land vehicles as an [[anti-theft system]] and as an emergency power off. Such devices are often placed in [[bait car]]s and configured so that observing police can trigger the switch remotely.<ref>{{cite news |newspaper=[[The New York Times]] 
  |url=https://www.nytimes.com/1994/04/24/automobiles/driving-smart-a-kill-switch-can-steal-a-car-thief-s-precious-time.html
  |title=A Kill Switch Can Steal a Car Thief's Previous Time |date=April 24, 1994}}</ref> This same idea can make the stolen object, such as a [[smartphone]], useless to both the thief and whoever buys it, yet allow the true owner to reactivate it when/if it is recovered.<ref>{{cite news |newspaper=[[The New York Times]] 
|url=https://bits.blogs.nytimes.com/2014/06/19/antitheft-technology-led-to-a-dip-in-iphone-thefts-in-some-cities-police-say
|title=Smartphones Embracing 'Kill Switches' as Theft Defense |date=June 9, 2014}}</ref>

===Smartphones===
{{main|Smartphone kill switch}}
In [[smartphones]], a kill switch is a security feature that allows the phone's owner to remotely render the smartphone inoperable if it is lost or stolen. From 2015 this feature is legally required in [[California]] for smartphones.<ref>{{cite news
  |title=The Smartphone Kill Switch Explained
  |url=https://www.washingtonpost.com/news/the-switch/wp/2014/08/27/the-smartphone-kill-switch-explained
  |newspaper=[[The Washington Post]]}}</ref> There are also ''hardware kill switches'' on some phones, such as [[PinePhone]], where the user can, by moving a hardware switch inside the phone, disable hardware like the camera, microphone, Wi-Fi or LTE.<ref name=tuxphones>{{cite web |last1=T. |first1=Raffaele 
|title=Librem 5 vs. PinePhone: comparison of two Linux smartphones
|url=https://tuxphones.com/purism-librem-5-vs-pine64-pinephone-linux-smartphone-comparison/ |website=TuxPhones |language=en |date=2 September 2019}}</ref>
{{Further|Kill Pill}}

===Software===
: ''See also [[Brick (electronics)]] – an electronic device that can no longer function due to software malfunction''

By analogy to physical kill switches, "kill switch" can be used to refer to a mechanism incorporated in software that can be activated by its manufacturer or licensor, for example if the product is withdrawn, or a maintenance fee has not been paid, or a device has been lost or stolen.<ref>{{cite web|url=https://www.slashgear.com/microsoft-remote-software-kill-switch-confirmed-1656965/|title=Microsoft remote software "kill switch" confirmed|last=Davies|first=Chris|date=19 Sep 2009|website=SlashGear|access-date=10 May 2017}}</ref><ref>{{cite web|url=http://www.pcworld.com/article/2367480/10-things-to-know-about-the-smartphone-kill-switch.html|title=10 things to know about the smartphone kill switch|last=Williams|first=Martyn|date=24 Jun 2014|website=PCWorld|access-date=10 May 2017}}</ref> It can also refer to kill switches for the stopping of [[malware]] such as in the [[WannaCry ransomware attack]].<ref>{{cite web|last1=Chan|first1=Sewell|last2=Scott|first2=Mark|title=Cyberattack's Impact Could Worsen in 'Second Wave' of Ransomware|url=https://www.nytimes.com/2017/05/14/world/europe/cyberattacks-hack-computers-monday.html|work=The New York Times|access-date=14 May 2017|date=14 May 2017}}</ref><ref>{{cite web|title=Warning: Blockbuster 'WannaCry' malware could just be getting started|url=https://www.nbcnews.com/news/us-news/blockbuster-wannacry-malware-could-just-be-getting-started-experts-n759356|publisher=NBC News|access-date=14 May 2017|language=en}}</ref> 

There is a debate about implementing kill switches in [[robot]]s<ref>{{cite news
  |last1=Kottasova |first1=Ivana
  |title=Europe calls for mandatory 'kill switches' on robots
  |url=https://money.cnn.com/2017/01/12/technology/robot-law-killer-switch-taxes
  |publisher=CNNMoney |access-date=May 14, 2017|date=January 12, 2017}}</ref> and advanced [[artificial intelligence]] systems.<ref>{{cite web
|last1=Larson |first1=Selena |title=Killing the immortal: Why scientists are debating the life span of robots
|url=https://money.cnn.com/2017/01/26/technology/kill-switch-ai-ethics
|publisher=CNNMoney |access-date=May 14, 2017|date=January 26, 2017}}</ref>

====In AI====
{{See also|AI capability control#Interruptibility and off-switch}}
[[Google]] started to work on a hardware kill switch for [[AI]] in 2016.<ref>{{Cite news |date=2016-06-08 |title=Google developing kill switch for AI |language=en-GB |work=BBC News |url=https://www.bbc.com/news/technology-36472140 |access-date=2023-04-21}}</ref>

==Industrial machinery==
[[File:Emergency stop button.jpg|thumb|The arrows indicate that the stop button must be turned to [[Reset button|reset]] the switch before the equipment can be restarted.|alt=]]
On large industrial machines, an emergency stop button is typically located on the panel, and possibly in several other areas of the machine. Often, an emergency stop is made wireless using a remote control. This provides a rapid means to disconnect the energy source of the device to protect workers.<ref>{{cite web
   |author=Repas, Robert |date=June 22, 2010
   |url=http://machinedesign.com/article/designing-with-e-stop-switches-0622
   |title=Designing with E-stop Switches
   |archive-url=https://web.archive.org/web/20130417042555/http://machinedesign.com/article/designing-with-e-stop-switches-0622
   |archive-date=2013-04-17
   |website=machinedesign.com}}</ref> For [[fail-safe]] operation, the emergency stop button is a normally closed switch, which ensures that a broken wire will not prevent it from being activated, but may accidentally activate the emergency stop.

In the [[European Union]], most types of machinery are required to be equipped with an emergency stop according to the [[Machinery Directive|Directive 2006/42/EC]]. Exceptions apply for machinery in which an emergency stop would not lessen the risk as well as for portable hand-held/hand-guided machinery.

===Nuclear power plants===
{{main|Scram}}
A kill switch in a nuclear reactor plant is called [[Scram|SCRAM]]. It is usually characterized as an acronym for "safety control rod axe man", though this is probably a [[backronym]].

==Machine tools==
Emergency stop functions are frequently used on [[Machine_tool|machine tools]], including equipment like wood and metal [[Saw|sawing machines]], [[Grinding_machine|grinding machines]], [[Drill|drilling machines]], [[Milling_(machining)|milling machines and machining centres]] and [[Lathe|lathes]]. The emergency stop [[Functional_safety|safety function]], and general requirements for emergency stop devices are set out in ISO 13850. <ref name="ISO_13850">{{cite web |title=ISO 13850:2015 Safety of machinery — Emergency stop function — Principles for design |url=https://www.iso.org/standard/59970.html |website=iso.org |publisher=International Organization for Standardization |access-date=14 April 2022}}</ref> Machine specific (type-C) standards often include specific requirements for the emergency stop functions, but in the absence of a relevant type-C standard, the [[risk assessment]] should be used to determine whether or not an emergency stop function would be useful in avoiding or limiting harm. The ISO machinery safety standard types are defined in ISO 12100,<ref name="ISO_12100">{{cite web |title=ISO 12100:2010 Safety of machinery — General principles for design — Risk assessment and risk reduction |url=https://www.iso.org/standard/51528.html |website=iso.org |publisher=International Organization for Standardization |access-date=14 April 2022}}</ref> and this nomenclature is used by other standards development organizations, like [[American_National_Standards_Institute|ANSI]] in the US, and [[CSA_Group|CSA]] in Canada.<ref name="ANSI_B11-0">{{cite web |title=ANSI B11.0-2020 Safety Of Machinery |url=https://webstore.ansi.org/Standards/AMT/ANSIB112020 |website=ansi.org |publisher=American National Standards Institute |access-date=14 April 2022}}</ref><ref name="Z432-16">{{cite web |title=Z432-16 (R2021) Safeguarding of machinery |url=https://www.csagroup.org/store/product/Z432-16/ |website=csagroup.org |publisher=Canadian Standards Organization |access-date=14 April 2022}}</ref>

===Complementary protective measure===
[[File:Homemade Mollyguard.jpg|thumb|An emergency stop button with a custom-made plastic molly guard to prevent it from being pressed accidentally]]
A machinery's emergency stop control is considered a complementary protective measure<ref name="ISO_12100"/> because it is intended to complement the primary safeguarding measures like [[Machine_guarding|fixed guards, movable interlocked guards or safeguarding devices]]. The primary safeguarding measures prevent injury automatically, either by enforcing distance between a hazard and a person, or by eliminating the hazard by stopping hazardous motion or switching off a source of hazardous energy.

By contrast, an emergency stop requires a deliberate action on the part of a person who must first recognize that some hazardous condition is about to arise or is arising, and who then must activate the emergency stop function by pressing the emergency stop button or activating another emergency stop device such as a pull-cord switch.

==Fuel stations and road vehicles==
A kill switch is also used for [[fuel dispenser|gasoline pumps]] or any other device that pumps large amounts of [[explosive material|explosive]] or [[flammability|flammable]] [[chemical substance|chemicals]].  There is commonly a single kill switch for all pumps at a [[pumping station]].

==Elevators and escalators==
[[Elevator]]s<ref name=ElevatorEMbrakeFailedNYT2015>{{cite news |newspaper=[[The New York Times]] 
   |url=https://www.nytimes.com/2015/10/04/nyregion/deadly-elevator-fall-spurs-look-at-brakes-and-load.html
   |title=Deadly Elevator Fall Spurs Look at Brakes and Load
   |author=Benjamin Mueller  |date=October 3, 2015  |access-date=January 3, 2022}}</ref><ref name=ElevatorCableWorkedNYT2000>{{cite news |newspaper=[[The New York Times]] 
|url=https://www.nytimes.com/2000/01/26/nyregion/elevator-cable-failed-at-empire-state-building-city-finds.html
|title=Elevator Cable Failed at Empire State Building, City Finds
|author=C. J. Chivers |date=January 26, 2000  |access-date=January 3, 2022}}</ref><!---By way of comparison, the 2015 case was a major failure, the 2000 case was a partial failure/no deaths--> often have a red two-way button on the control panel which is either marked "Emergency Stop" or "Run/Stop". Normally, the button is in the "up" or unpushed position, allowing the elevator to "run" in normal service. When the button is pushed, the elevator comes to an immediate stop. When the button is pulled back out, it resumes normal service, thus the reason for the use of the phrase "Run/Stop". [[Escalator]]s will typically have a key-operated control that will turn the escalator off, or change its direction to up or down. Next to the key switch will be a red "Emergency Stop" button, which is used in the event of equipment failure, or where there is a potential for injury, such as when someone's shoe gets stuck in the "comb" at the top or bottom of the escalator and there is a risk of serious injury. The key switch is used to return the escalator to service after it has been stopped.<ref name=Elevator3dayStopNYT2005>{{cite news |newspaper=[[The New York Times]] 
   |url=https://www.nytimes.com/2005/04/06/nyregion/3-hungry-days-for-deliveryman-stuck-in-elevator.html
   |title=3 Hungry Days for Deliveryman Stuck in Elevator
   |quote=intercom .. emergency alarm button .. emergency stop switch
   |author=Michael Wilson |date=April 6, 2005 |access-date=January 4, 2023}}</ref><ref name=EscalatorNYT1989>{{cite news |newspaper=[[The New York Times]] 
|url=https://www.nytimes.com/1989/04/29/style/consumer-s-world-escalator-dangers-called-preventable.html
|title=Escalator Dangers Called Preventable
|quote=emergency shut-off switches on escalators.
|author=Michael Decourcy Hinds |date=April 29, 1989  |access-date=January 4, 2023}}</ref>

==Gym==
[[Treadmill]]s<ref>{{cite news |newspaper=[[The New York Times]]
  |url=http://well.blogs.nytimes.com/2009/05/27/the-danger-of-treadmills
  |title=The Dangers of Treadmills |first=Tara |last=Parker-Pope  |date=May 27, 2009|access-date=January 22, 2009}} ("the cord yanks the key out of the console and the treadmill stops")</ref> often use a safety key with one end magnetically attached to the machine and the other end clipped to the user's waist. If the safety key is pulled out, such as in the event of a fall, the treadmill stops immediately. In other cases, some other treadmills have a more traditional kill switch, often mounted towards the rear of one of the hand railings.<ref>{{cite web
|url=https://www.google.com/search?q=%22treadmill%22+%28%28emergency+stop%29+OR+%28kill+switch
|title="treadmill" ((emergency stop) OR (kill switch))}}</ref><ref>{{cite web |url=https://services.gehealthcare.in/gehcstorefront/p/88380-00
  |title=Emergency Stop Switch Treadmill T2100 with Bracket
  |work=GE Healthcare |quote=The emergency stop switch is a safety device used in emergency situations to stop the treadmill}}</ref>

==Amusement rides==
The emergency stop on an [[amusement ride]] is similar to that on industrial equipment.  Typically brakes on a ride are designed to be disengaged when power is applied; disconnecting power will cause all brakes to engage.  Most amusement rides have a computer that can, similar to the rail example provided above, engage the emergency stop when such a ride is determined to be out of operating specification, or an accident involving a passenger or ride employee has happened.<ref name=MusementParkWWAYTV32021>{{cite news |publisher=[[WWAYTV3]] (CBS)
   |url=https://www.wwaytv3.com/viral-video-of-malfunctioning-amusement-park-ride-prompts-question-how-safe-are-rides-in-nc/
   |title=Viral video of malfunctioning amusement park ride prompts question: How sare are rides in NC
   |date=July 13, 2021 |access-date=January 4, 2023}}</ref>

==Spaceflight==
[[Range safety]] systems can automatically destroy errant vehicles in-flight. Range-safety officers may also manually destroy vehicles; this method was used to destruct errant [[solid rocket boosters]] in the [[Space Shuttle Challenger disaster|Space Shuttle ''Challenger'' disaster]].

==See also==
* {{annotated link|Internet kill switch}}
* {{annotated link|Blue light station}}
* {{annotated link|Battleshort}}, even if damage or injury will occur; the opposite of a kill switch
* {{annotated link|Emergency brake (train)}}

==References==
{{Reflist|30em}}

{{Switches}}
{{Authority control}}

{{DEFAULTSORT:Kill Switch}}
[[Category:Safety switches]]