Most storage devices that do not require vision and a brain to read data fall into this category. Electromagnetic data may be stored in either an analog data or digital data format on a variety of media.
Direct Tripwire Alarm - The wire placed across the path is directly connected with the cord, wire or string placed across the particular path. Laser Tripwire Alarm - An invisible laser, typically an infra-red, is used instead of a cord or string.
Safety wiring of two pairs of drilled bolt-heads wired one-to-the-other. Safety wire or locking-wire is a type of positive locking device that prevents fasteners from loosening or falling out due to vibration and other forces. The presence of safety wiring may also serve to indicate that the fasteners have been properly tightened.