Editing Dead man's switch (section)

==Types==
===Handle===
{{Redirect|Dead man's handle|the novel|Dead Man's Handle}}

Many dead man's switches are mounted in the control handle of a vehicle or machine and engage if the operator ever loses their grip.{{Citation needed|date=November 2023}}

====Vehicles====
Handle switches are still used on modern trams and trains. [[Pneumatic]]ally or electrically linked dead man's controls involve relatively simple modifications of the ''controller handle'', the device that regulates traction power. If pressure is not maintained on the controller, the train's emergency brakes are applied. Typically, the controller handle is a horizontal bar, rotated to apply the required power for the train. Attached to the bottom of the handle is a rod that when pushed down contacts a [[solenoid]] or switch inside the control housing. The handle springs up if pressure is removed, releasing the rod's contact with the internal switch, instantly cutting power and applying the brakes.

Though there are ways that this type of dead man's control could conceivably fail, in practice they have proven highly reliable. On some earlier equipment, pressure was not maintained on the entire controller, but on a large button protruding from the controller handle. This button also had to be pressed continuously, typically with the palm of the hand so that the button was flush with the top of the handle. Another method used, particularly with some lever-type controllers, which are rotated rather than pushed or pulled, requires that the handle on the lever be turned through 90 degrees and held in that position while the train is in operation. Some dead man's controls only work in the mid position and not with full pressure (see [[pilot valve]]).

In modern [[New York City Subway]] trains, for example, the dead man's switch is incorporated into the train's speed control. On the [[R142A (New York City Subway car)|R142A]] car, the train operator must continually hold the lever in place in order for the train to move.

An example of a passenger vehicle using a dead man's switch is on [[Tesla Inc|Tesla]] electric vehicles. When the driver has engaged the semi-autonomous driving system "Autopilot", they must keep their hands on the steering wheel. If the driver takes their hands off the steering wheel for more than 30 seconds, a loud alarm will sound inside the car to wake sleeping drivers; if the driver leaves their hands off for more than a minute, then the car will engage its hazard warning lights and bring the car to a stop. This is done because the Autopilot system is not capable of full-self driving, and requires that the driver be able to take over operation of the vehicle without warning, should the car encounter a problem it does not know how to solve. This system uses a torque sensor on the steering wheel of the vehicle: when a driver is simply holding the wheel, they are still applying a small amount of torque to the wheel, confirming for the car that the driver is being attentive; if the driver turns the wheel with more force, all vehicle controls are handed back to the driver immediately.<ref>{{Cite web |url=https://www.tesla.com/support/autopilot |title=Autopilot and Full Self-Driving Capability |date=February 13, 2019 |website=Tesla.com }}</ref><ref>{{cite web |url=https://fortune.com/2017/06/23/tesla-autopilot-technology-keep-drivers-alert/ | title=Tesla: Technology Helps to Keep Drivers Alert After Autopilot Crash |website=Fortune }}</ref><ref>{{Cite web |url=https://www.theverge.com/2018/5/14/17352814/elon-musk-tesla-autopilot-face-tracking-gm |title=Tesla Rejected More Advanced Driver Monitoring Features on Its Cars |first=Sean |last=O'Kane |date=May 14, 2018 |website=The Verge }}</ref>

====Machinery====
Handle-mounted dead man's switches are also used on many hand-held tools and lawn equipment, typically those that rotate or have blades such as saws, drills, [[snow blower]]s and lawn mowers. On saws for example, they incorporate a squeeze throttle trigger into the handle. If the user loses grip of the saw, the springs in the throttle trigger will push it back out to the off or idle setting, stopping the blade from spinning. Some tools go further and have a trigger guard built into the handle, similar to [[Safety (firearms)|firearm safeties]]. Only when the user presses in the trigger guard first will it then release its lock on the trigger and allow the trigger to be pressed in. Typically, trigger guards can only be pressed in while the user has a firm grip of the handle.{{Citation needed|date=November 2023}}

Every walk-behind mower sold in the US since 1982 has a dead man's switch called an "operator-presence control", which by law must stop the blades within three seconds after the user releases the controls.<ref>{{Cite web |url=http://www.gpo.gov/fdsys/pkg/CFR-2012-title16-vol2/xml/CFR-2012-title16-vol2-part1205.xml |title=SAFETY STANDARD FOR WALK-BEHIND POWER LAWN MOWERS |website=GPO.gov }}</ref> Attached across the handle is a mechanical lever connected by a flexible cable to the kill switch on the engine. While mowing, the operator must always squeeze the lever against the handle. If the operator ever loses grip of the handle, the blade will disengage or the engine will stop, stopping the blades from spinning and (if equipped) any drive wheels from turning.  On mowers where the engine stops, this switch configuration also acts as the engine's main kill switch; when the operator wants to stop the engine, he can release the dead man's switch intentionally.{{Citation needed|date=November 2023}}

===Touch sensor===
On some vehicles, including the diesel-electric railway locomotives in Canada, and on [[Nottingham Express Transit]] vehicles, the tram's speed controller is fitted with a capacitive touch sensor to detect the driver's hand.{{citation needed|date=September 2023}} If the hand is removed for more than a short period of time, the [[track brake]]s are activated.{{citation needed|date=September 2023}} Gloves, if worn, have to be finger-less for the touch sensor to operate. A backup dead-man's switch button is provided on the side of the controller for use in the case of a failed touch sensor or if it is too cold to remove gloves.{{citation needed|date=September 2023}}

===Pedal===
[[File:SIFA-Pedal.jpg|thumb|Dead-man's vigilance device (here a pedal) on the cab car of a German InterCity train]]
A pedal can be used instead of a handle. While some pedal switches must simply be held down in order for the machine to function (this system is often found on amusement rides, where the operator is likely to remain in a standing position for a lengthy period of time while the ride is in motion), this method has some shortcomings. In the [[Waterfall train disaster]], south of Sydney, Australia, in 2003, the driver suddenly died of a heart attack, and his slumped body kept the pedal depressed.

There are some solutions to this issue that are now used in modern pedal systems. The pedal can have a vigilance function built in (a '''dead-man's vigilance device''', '''driver vigilance device''' or '''DVD'''),<ref>{{Cite web |url=https://www.rssb.co.uk/research-development-and-innovation/research-project-catalogue/t024 |title=Driver Vigilance Devices – Systems Review (T024) |website=RSSB.co.uk |archive-url=https://web.archive.org/web/20180804075725/https://www.rssb.co.uk/research-development-and-innovation/research-project-catalogue/t024 |archive-date=2018-08-04 |access-date=2018-08-04 }}</ref> where drivers must release and re-press the pedal in response to an audible signal. This prevents it from being defeated by the above circumstances and is a standard feature on most British DSD systems.<ref>{{cite web|url=http://locodocs.co.uk/brmanuals/DSD-33056-4-Issue1.htm |title=Locomotive Repair Books, Record Cards, Manuals and Driver's Handbooks |website=LocoDocs.co.uk |access-date=2013-11-15}}</ref> If the timer period is beginning to expire, a visual and audible warning is given. If the operator fails to acknowledge the warning, a [[penalty brake]] application results.

Some types of locomotive are fitted with a three-position pedal, which must normally be kept in the mid position. This lessens the likelihood of accidentally defeating it, although it may still be possible to deliberately do so. Adding a vigilance function to this type of pedal results in a very safe system. However, isolation devices are still provided in case of equipment failure, so a deliberate override is still possible. These isolation devices usually have tamper-evident seals fitted for that reason.

===Seat switches===
The dead man's switch can also be located beneath the seat of a vehicle or machine and engages if the operator is not in the seat holding the switch down. On modern tractors, the switch will cut the engine while the transmission is engaged or the [[power take-off]] is spinning. On riding lawn mowers, the switch is often more extreme where the switch will cut the engine even if the mower is parked and the blades are not spinning. Seat switches can also be used to keep small children from even starting the vehicle since they would not weigh enough to completely hold down a switch adjusted to an adolescent's or adult's weight.

===Key switches===
On recreational vehicles such as boats, [[personal watercraft]] and snowmobiles, and on the control panel of many [[amusement ride]]s, the user or operator has a cord or lanyard attached to their wrist or life jacket, that is in turn attached to a [[Key switch|key]] mounted on the dead man's switch. Should the rider fall off the vehicle or the operator at least move away from the controls, the cord will be pulled out of the dead man's switch, turning off the engine or setting the throttle position to "idle". On powered boats in particular this cord is often called a "kill cord" (for powered boats use around the wrist is not recommended, as it may slip off without cutting the engine).<ref>{{cite web|url=http://www.rya.org.uk/cruising/safety/Pages/Useyourkillcord.aspx|archive-url=https://web.archive.org/web/20130117003954/http://www.rya.org.uk/cruising/safety/Pages/Useyourkillcord.aspx|archive-date=2013-01-17|access-date=2013-05-07|title=Use your kill cord|publisher=[[Royal Yachting Association]]|website=RYA.org.uk}}</ref><ref>{{Cite web|date=2020-02-14|title=Kill Cords|url=https://chieftain.training/kill-cords/|access-date=2020-06-03|website=Chieftain Training|language=en-GB}}</ref> If the helmsman goes overboard or is forced away from the controls, the engine cuts out. This prevents the boat from continuing under power but out of control, risking injury to anyone in or out of the water including passengers who may have fallen out or may still be in the boat, and collision damage to any property in the path of this out of control boat; this in turn prevents or limits damage to the boat itself from striking other objects. It is a common and dangerous practice to defeat the kill cord by fixing it to part of the boat instead of the operator; for convenience. This has been the cause of accidents, some of which were fatal or caused limb loss.<ref>{{cite news |first=Steven |last=Morris |url=https://www.theguardian.com/world/2013/may/06/cornwall-speedboat-accident-police-rescuers |title=Cornwall speedboat accident: police pay tribute to rescuers |work=[[The Guardian]] |date= 6 May 2013|access-date=2013-11-15}}</ref>

Some luggage carts at airports and exercise [[treadmill]]s have this feature. In the case of treadmills, the dead man's switch usually consists of an external magnet attached to a cord that clips to the user. If the user falls or walks away without turning off the treadmill, the switch cuts power to the treadmill belt.

In [[Physical information security|information security]], kill cords are also used in computers to turn off the machine if the user is separated from it.<ref>{{cite news |first=Anton |last=Shilov |url=https://www.tomshardware.com/news/buskill-usb-cable-now-available-a-pc-kill-switch-for-data-protection |title=BusKill USB Cable Now Available: A PC Kill Switch for Data Protection |work=[[Tom's Hardware]] |date=15 Dec 2021|access-date=2022-07-02}}</ref><ref>{{cite news |first=Jean-Luc |last=Aufranc |url=https://www.cnx-software.com/2021/12/15/buskill-usb-kill-cord-protects-data-on-linux-windows-mac-os-devices/ |title=BusKill USB kill cord protects data on Linux, Windows, Mac OS devices |work=CNX Software |date=15 Dec 2021 |access-date=2022-07-02}}</ref>

===Altimeter switches===
[[Strategic Air Command]] developed a dead man's switch for its nuclear bombers, known as [[Special Weapons Emergency Separation System]] (SWESS), that ensured the nuclear payload detonated in the event of the crew becoming incapacitated through enemy action. The purpose of this device, unlike other examples mentioned above, was [[fail-deadly]] rather than [[fail-safe]]. Once armed, the system would detonate the onboard nuclear weapons if the aircraft dropped below a predetermined level,<ref>{{cite book|title=The Limits of Safety|first=Scott Douglas|last=Sagan|url=https://books.google.com/books?id=9eE9DwAAQBAJ&q=SWESS&pg=PA187|isbn=0-691-02101-5|publisher=Princeton University Press|year=1995|access-date=2008-11-16|pages=187–188}}</ref> typically due to being shot down.