Tripwire


A tripwire is a passive :wikt:trigger|triggering mechanism. Typically, a wire or cord is attached to some device for detecting or reacting to physical movement.

Military applications

Such tripwires may be attached to one or more mines — especially fragmentation or bouncing mines — in order to increase the area where triggering may occur.. Trip wires are frequently used in booby traps -- where either a tug on the wire, or the release of tension on it, will trigger the explosives.
Soldiers sometimes detect the presence of tripwires by spraying the area with Silly String. It will settle to the ground in areas where there are no wires. Where wires are present, the "strings" will rest on the taut wires without triggering the explosive, due to its light weight. It was used by U.S. troops in Iraq for this purpose.
Another detection method is the use of green line lasers to illuminate and thus expose trip and command wires. The bright laser beam reflects off of the tripwire and can be seen by the user.

Industrial applications

A tripwire may be installed in the vicinity of industrial equipment, such as a conveyor belt to enable workers to stop the equipment quickly. These may also be called emergency stop pull-cords.