A dead man's switch (for other names, see alternative names), as its name suggests, is a device intended to stop a machine in case the human operator becomes incapacitated, and is a form of fail-safe. A dead man's switch (for other names see alternative names) as its name suggests is a switch that is automatically operated in case the Human operator becomes incapacitated Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus Fail-safe or fail-secure describes a device or feature which in the event of failure, responds in a way that will cause no harm or at least a minimum of harm They are commonly used in locomotives, freight elevators, lawn mowers, tractors, jet skis, outboard motors, chainsaws, snowblowers and snowmobiles. A locomotive is a railway Vehicle that provides the motive power for a Train. An elevator or lift is a Transport device used to move people or goods vertically from one floor to another A lawn mower or lawnmower is a machine that has one or more revolving blades to cut a Lawn at an even length A tractor is a Vehicle specifically designed to deliver a high Tractive effort at slow speeds for the purposes of hauling a trailer or machinery used Jet Ski is the Brand name of Personal watercraft (PWC manufactured by Kawasaki Heavy Industries Ltd An outboard motor is a propulsion system for smaller Boats General uses Outboard motors for a Boat are developed as a self-contained A chainsaw (or chain saw) is a portable mechanical motorized Saw. A snow blower, snowblower, or snow thrower is a machine for removing Snow from an area where it is not wanted such as a Driveway, Sidewalk A snowmobile (known locally as snowmachine, snowsled or by the Brandname Ski-Doo) is a land vehicle that is commonly propelled by
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Background
Interest in dead-man's controls increased with the introduction of electric streetcars and especially electrified rapid transit trains, though dead-man equipment was quite rare on US streetcars until comparatively recently. A tram, tramcar, trolley, trolley car, or streetcar is a railborne vehicle, of lighter weight and construction than a Train A rapid transit, underground, subway, elevated railway or metro(politan system is an electric passenger railway In conventional steam railroad trains, there was always a second person with the engineer, the fireman, who could bring the train to a stop if necessary. Steam railroad is a term used in the United States to distinguish conventional heavy Railroads from Street railways Interurban streetcar lines For many decades this practice continued on electric & diesel locomotives, even though a single person could theoretically operate them. Diesel or Diesel fuel (ˈdiːzəl in general is any Fuel used in Diesel engines The most common is a specific fractional distillate of petroleum A locomotive is a railway Vehicle that provides the motive power for a Train.
With modern urban and suburban railway systems, the driver was typically alone in an enclosed cab. South San Jose (cropjpg||thumb|A suburban development in San Jose California. Though automatic devices were already beginning to be deployed on newer installations of the New York City Subway system in the early 20th century, it took the disastrous Malbone Street Wreck on the Brooklyn Rapid Transit system in 1918 to point out the need for universal deployment of such devices to halt trains in the event of an operator's disability. The New York City Subway is a Rapid transit system owned by the City of New York and leased to the New York City Transit Authority, a subsidiary agency The twentieth century of the Common Era began on The Malbone Street Wreck, also known as the Brighton Beach Line Accident of the Brooklyn Rapid Transit Company (BRT was a Rapid transit railroad accident The Brooklyn Rapid Transit Company (BRT was a Public transit Holding company formed in 1896 to acquire and consolidate lines in Brooklyn and Queens Year 1918 ( MCMXVIII) was a Common year starting on Tuesday (link will display the full calendar of the Gregorian calendar (or a Common
Types
Handle
Pneumatically or electrically linked dead-man's controls, still used today, involve relatively simple modifications of the controller handle, the device that regulates traction power. Pneumatics, Pressurized gas to affect mechanical motion Pneumatic power is used in Industry, where it is common to have factory units plumbed for Compressed The main requirement is that the train's emergency brakes are applied if pressure is not maintained on the controller.
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 which, when pushed down, contacts a solenoid or switch inside the control housing. A solenoid is a three-dimensional Coil. In Physics, the term solenoid refers to a loop of wire often wrapped around a Metallic core which 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, 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 pushed or pulled rather than rotated, 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 require the motorman to hold it in the mid-position rather than apply full pressure (see pilot valve). A pilot valve is a small Valve that controls a limited-flow control feed to a separate piloted valve
In many modern New York Subway trains, for example, the dead man's switch is incorporated into the train's speed control. The New York City Subway is a Rapid transit system owned by the City of New York and leased to the New York City Transit Authority, a subsidiary agency On the R142A the train operator must continually hold the lever in place. The R142A, along with the R142 is the newest generation of cars for the New York Subway 's IRT division This was depicted in the movie and book The Taking of Pelham 123, in which a group of men hijack a New York City subway train for ransom, but because of the Dead-man's feature, cannot escape while the train is moving. The Taking of Pelham One Two Three (also known as The Taking of Pelham 123) is a thriller movie released in 1974. Hijacking means to take over by force. Hijacking may refer to In property: Aircraft hijacking or 'skyjacking' Ransom is the practice of holding a prisoner to extort money or property to secure their release or it can refer to the sum of money involved
Every lawn mower sold in the US since 1982 has an "operator-presence" device, which by law must stop the blades within 3 seconds after the user lets go of the controls[1].
Touch Sensor
On the Nottingham Express Transit vehicles, the tram's speed controller is fitted with a capacitive touch sensor to detect the driver’s hand. Nottingham Express Transit (or in short NET) is a light-rail Tramway in the Nottingham area in England. A tram, tramcar, trolley, trolley car, or streetcar is a railborne vehicle, of lighter weight and construction than a Train If the hand is removed for more than a short period of time, the track brakes are activated. Track brakes are a form of Brakes unique to railborne vehicles Gloves, if worn, have to be finger-less for the touch sensor to operate. A back up 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.
Pedal
A pedal can be used instead of a handle. In the Waterfall train disaster, it appeared that the driver, who was overweight, slumped on his seat, kept the pedal pressed when he died. In the movie Silver Streak, a man hijacks the train and keeps it running by placing a heavy toolbox on the pedal. Silver Streak is a 1976 comedy, action and Mystery film about murder on a Los Angeles -to- Chicago train journey
Seat Switches
On tractors, the switch is beneath the seat, and will cut the engine if the operator gets off the tractor while the transmission is engaged or the power take-off is spinning. A power take-off ( PTO) is a splined Driveshaft, usually on a Tractor or that can be used to provide power to an attachment or separate machine
Key Switches
On recreational water vehicles, such as jet skis and wave runners, the user has the ignition key attached to his wrist or waist by a leash. The key will be removed from the ignition switch if the rider falls into the water, thus turning off the engine.
Vigilance control
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. A dead-man's vigilance device is a Railroad safety device that operates in the case of incapacitation of the engineer. 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.
Something that could be considered an early vigilance control device is the one-legged stool issued to watchmen: If the watchman were to fall asleep on his stool, he would fall over and be woken.
There has also been a proposal to introduce a similar system to automotive cruise controls. Cruise control (sometimes known as speed control or autocruise) is a system that automatically controls the rate of motion of a Motor vehicle.
A hybrid between a dead man's switch and a vigilance control device is a dead-man's vigilance device. A dead-man's vigilance device is a Railroad safety device that operates in the case of incapacitation of the engineer.
Software uses
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 notification to friends or deleting and encrypting data. The "non-event" triggering these can be almost anything, such as failing to log in consecutively for a week, not responding to an automated e-mail 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 boot. Electronic mail, often abbreviated to e-mail, email, or originally eMail, is a Store-and-forward method of writing sending receiving Ping is a Computer network tool used to test whether a particular host is reachable across an IP network it is also used to self test the network interface Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth Basic principle A traditional landline telephone system also known as "plain old telephone service" (POTS, commonly handles both signaling and audio information In Computing, booting ( booting up) is a bootstrapping process that starts Operating systems when the user turns on a Computer system Motivations vary, depending on the individual's needs. For example, somebody in a police state may be concerned about the security of their data (or deleting it), while others may just wish to alert friends or the authorities by e-mail that something undesirable might be going on.
Miscellaneous uses
Dead man's switch devices have also been used in suicide bombing, to trigger the explosive if the bomber is shot or overpowered. This article is about suicide attacks for political and/or military reasons This is a fail-deadly mechanism, rather than a fail-safe mechanism. Fail-deadly is a concept in nuclear Military strategy which encourages deterrence by guaranteeing an immediate automatic and overwhelming response Fail-safe or fail-secure describes a device or feature which in the event of failure, responds in a way that will cause no harm or at least a minimum of harm
Alternative names
- Driver's Safety Device (DSD) is the official UK railway term. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located
- Dead man's pedal
- Dead man's handle
- Dead man's control
- Dead man's brake
- Kill Switch
- Vigilance control
- Live-man switch
Event recording
The status and operation of both the vigilance and dead-man's may be recorded on the train's event recorder (commonly known as a black box). Train event recorders are similar to flight data recorders found on aircraft
See also
External links
A dead-man's vigilance device is a Railroad safety device that operates in the case of incapacitation of the engineer. A train protection system is a railway technical installation to ensure safe operation in the presence of human failures Types of brakes While both hand-operated systems and foot-operated system serve for parking brakes the hand-operated systems are more useful in other situationsDapyx Software network: MP3 Explorer | Ebook Manager | Zenithic