dead man's switch

[victor steinbok]

Unless I missed something in the search (for which I blame the editors, of
course), the expression is not in the OED in any variation (dead man switch,
dead men switch, dead men's switch, deadman switch, etc.).

The 1974 original of "Taking of Pelham One Two Three" refers to "deadman
feature", which is a rig standard on trains and some buses that requires the
operator to exert constant pressure or the vehicle would come to a stop. In
pop culture--particularly in films involving terrorists or bank robbers with
self-strapped bombs--a "dead man's switch" is a lever on a remote detonator
that has to be depressed to prevent an immediate detonation (or,
occasionally, it is a button that must always be pressed). It's the
equivalent of a spring-lever on a hand-grenade--which allows the grenade to
be thrown safely once the pin is removed. I am not sure how widespread the
term is in the military, but, if it is, it may well have been reverse
distribution from pop-culture, which acquired the terminology from public
transportation (more specifically, apparently, from electric trains). The
OED /does/ have an entry for the train switch, but it's somewhat different.

Dead man's handle

>  In an electric train, a controlling handle which must be held in position
> for the current to pass, so that the train is automatically brought to a
> standstill should the driver release his grasp through illness or accident.
> So dead man's device, dead man's knob, dead man's pedal, dead man's treadle.
> Also transf.


I suppose, device and feature are interchangeable in their vagueness. But
there is still no "switch". There is also "deadman brake", which is what I
heard from operators on the MBTA Green Line (the T).

The earliest for "dead man's handle/knob" in the OED is 1908 (includes both
knob and handle). Ironically, the switch makes its appearance in the same
year.

http://goo.gl/1aOh4
Bulletin of the International Railway Congress Association (English
Edition).
Volume 22 (9). September 1908
Electric Traction by Simple Alternating Current on European Railways. By H.
Marchand-Thriar. VIII.--The Thomson-Houston Company's System. p. 1023

> The master-controller is fitted with a safety handle (dead man's switch) so
> arranged that if the driver fell or fainted, his releasing the handle would
> ensure the current being cut off automatically from all the vehicles.

Volume 22(11). November 1908
Notes Taken During a Journey of Enquiry in the United States. By Em.
Uytborck. p. 1217

> The cars are equipped with the system of control known as the "Sprague
> General Electric"; the controller is fitted with a dead-man's switch (i.e.
> it returns to neutral if the driver releases the handle).



Note, however, that the authors of /both/ articles were Belgian, which may
well be an issue worth investigating (unless earlier instances are found).

http://goo.gl/1ZGSF
Electric Trains. By Reginald Ernest Dickinson. 1927 [snippet view: title
page shows Edward Arnold & Co. 1927]
p. 67

> The driver then depressed the Dead Man's Switch with his right hand, which
> must remain on the controller handle throughout all driving operations, and
> pushes the reverser key to the position marked "forward".

p. 68

> ...[Cut]ting off all power to the train the opening of the Dead Man's
> Switch has the effect of applying the brakes by the following means.


Interestingly, a sentence from p. 62 of this same book is cited in the OED
for reverser n. 1.c. (I guess, that confirms the date.)

The use diversified very quickly--it could be an ignition switch on a racing
motorcycle, fork-lift starter, a shut-off valve on an automatic welder or a
fuel system for filling airplanes, a paddle on the steering mechanism of a
motor boat, a buoy-releasing mechanism on a submarine, a quick-release
switch for switching over from "receive" to "transmit" on a ham radio, etc.

A couple of samples:

There is a picture and construction plan for a dead man's switch in 1974
Popular Mechanics. (There are similar devices in 1957 Popular Mechanics and
Popular Science.)

http://goo.gl/ZUVpu
Popular Mechanics. May 1974
Backpack paint-removing machine. By Parry C. Yob. p. 154

> The purpose of this dead-man's switch is to provide a safety feature when
> you're working from ladders and scaffoldings.



It also makes an appearance in the 1970 DOD appropriations hearings (1969)
in a description of locator buoy for a submarine.

http://goo.gl/YcgWe

> The system will release the buoy when ... (3) a dead-man's switch is not
> reset by the crew at two hour intervals. The dead-man's switch has an alarm
> which warns the crew several minutes before release. The dead-man's switch
> ensures release of the buoy should the entire crew become incapacitated.



I am not including other GB hits (from 1932 to 1980--more train entries from
the 1920s), but there is a total of 94 (with duplicates) of them
pre-1980--and that's just for "dead-man's-switch". I ignored the rest, for
the moment.

But one thing that does not appear is explosives. So the pop-culture
terrorist "dead man's switch" appeared much later.


Another pair of expressions that is related--in both senses--is "fail-safe"
and "fail-deadly". Fail-safe is very common as a noun, and there is a
fail-safe entry in the OED, but it's a verb under fail v. 4.b. There is no
entry for fail-deadly, which is the equivalent of a doomsday machine (or
bomb or device--the expression going back to at least 1606)--"fail-deadly"
is old jargon for the Cold War feature of a retaliatory nuclear strike in
case that the command structure is wiped out. It was meant as a joke on
"fail-safe", which is why it is puzzling that the latter noun has no OED
entry. Again, I have not tracked the specific origin or distribution of
either expression.

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