Editing Dead man's switch (section)

==Vigilance control==
{{see also|Sifa}}

The main safety failing with the basic dead man's system is the possibility of the operating device being held permanently in position, either deliberately or accidentally. Vigilance control was developed to detect this condition by requiring that the dead man's device be released momentarily and re-applied at timed intervals. There has also been a proposal to introduce a similar system to automotive [[cruise control]]s.<ref>{{Cite web |title=How to Install a Deadman Switch? |url=https://fordnews.org/ranger/how-to-install-a-deadman-switch.html |website=FordNews.org |access-date=2022-11-02 }}</ref>

===Software===
[[Software]] versions of dead man's switches are generally only used by people with technical expertise, and can serve several purposes, such as sending a stored message, a notification to friends, or deleting and [[encryption|encrypting]] data. The "non-event" triggering these can be almost anything, such as failing to [[log in]] for 7 consecutive days, not responding to an automated e-mail, [[Ping (networking utility)|ping]], a [[GPS]]-enabled telephone not moving for a period of time, or merely failing to type a code within a few minutes of a computer's [[Booting|boot]]. An example of a software-based dead man's switch is one that starts when the computer boots up and can encrypt or delete user-specified data if an unauthorized user should ever gain access to the protected computer. Google's Inactive Account Manager<ref>{{cite web |url=https://support.google.com/accounts/answer/3036546?hl=en |title=About Inactive Account Manager |website=Google Help |access-date=2019-07-05 }}</ref> allows the account holder to nominate someone else to access their services if not used for an extended period (the default is three months). Some solutions available to the public utilize the growing market of mobile devices. Instead of sending an automated e-mail, they will send a push notification directly to the mobile device,<ref>{{Cite web|url=https://www.Deadmanswitch.com/|title=Deadmanswitch|website=Deadmanswitch.com |access-date=2022-01-14 }}</ref> and can alert family and friends in a much more convenient way.

===Spacecraft===
Many spacecraft use a form of dead man's switch to guard against command system failures. A timer is established that is normally reset by the receipt of any valid command (including one whose sole function is to reset the timer). If the timer expires, the spacecraft enters a "command loss" algorithm that cycles through a predefined sequence of hardware or software modes (such as the selection of a backup command receiver) until a valid command is received. The spacecraft may also enter a [[Safe mode (spacecraft)|safe mode]] to protect itself while waiting for further commands.

While having some similarities to a dead man's switch, this type of device (a command-loss timer) is not actually a dead man's switch, because it aims to recover from a hardware failure rather than the absence of human operators. It is generally called a [[watchdog timer]], and is also used extensively in nuclear power control systems. System components on a spacecraft that put it into a safe mode or cause it to execute default behaviors when no command is received within a predefined time window can be considered a dead man's switch, but hardware or software that attempts to receive a command from human operators through an alternate channel is an auto-recovering or adaptive communications system, not a dead man's switch. [[Voyager 2]] recovered from a command receiver failure with a command-loss timer.<ref>{{cite web|url=http://tmo.jpl.nasa.gov/progress_report2/42-49/49E.PDF|title=Voyager Support. DSN Progress Report 42-49|publisher=[[Jet Propulsion Laboratory]]|date=1978|access-date=4 March 2009|first1=J.|last1=Allen|first2=H.|last2=Nance}}</ref>

===Train===
In most trains, a basic level of protection is provided by a "dead man's handle" or pedal. If the driver is taken ill and releases this, the power will be shut off and an [[Emergency brake (train)|emergency brake]] application will be initiated to stop the train.

More recent safety standards do not consider this to be adequate, as the driver may slump over the dead man's handle and continue to hold it down even though they are not capable of controlling the train. Modern trains overcome this risk with the addition of a '''vigilance system'''<ref name="DSD ">{{cite web |title=DSD Vigilance Unit |url=http://www.arrowvale.co.uk/images/stories/rail/brochures/DSD_Vigilance_Unit.pdf |access-date=2017-08-17 |date=2010 }}{{Dead link|date=May 2025 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> to the dead man's system. A buzzer or bell sounds every minute or so in order to alert the motorman or engineer. If they do not respond by moving a controller, or releasing and then re-applying the dead man's handle, the system will automatically initiate an emergency brake application. Most major rail systems in the world use this equipment, both in their freight and passenger operations. It is also used on the [[R143 (New York City Subway car)|R143]] and other New York City Subway cars while under [[communications-based train control|CBTC]] operation. In the US, older locomotives produced before 1995 did not originally carry this feature, but given the modular nature of the system it is not uncommon to find them retrofitted.{{Citation needed|date=September 2023}}

===Aircraft===
[[Piper PA-46#PA-46-350P Malibu Mirage|Some aeroplanes]] use vigilance control to minimize [[Hypoxia (medical)#Generalized hypoxia|hypoxia]], descending to lower altitude if the pilot is unresponsive.<ref name=avw2015-04-berto>{{cite web |first=Paul |last=Bertorelli |url=http://www.avweb.com/blogs/insider/Piper-Bets-Big-on-Envelope-Protection-223847-1.html |title=Piper Bets Big on Envelope Protection |website=avweb.com |agency=Aviation Publishing Group |date=13 April 2015 |access-date=15 April 2015 |archive-date=28 December 2016 |archive-url=https://web.archive.org/web/20161228114231/http://www.avweb.com/blogs/insider/Piper-Bets-Big-on-Envelope-Protection-223847-1.html |url-status=dead }}</ref>

In 2019, the [[Garmin G3000]] became the first [[general aviation]] avionics suite capable of automatically diverting an aircraft to the nearest airport and landing it in the event a pilot fails to interact with the aircraft's controls or respond to system prompts. This automation capability has been made possible by advancements in computing, control, and navigation technologies and is of particular importance in a general aviation setting since private aircraft are often flown by only a single pilot.