Editing Dead man's switch (section)

===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}}