Motion Detection

This page is about mechanical and electronic motion detectors. For motion detection performed by people, animals, or other organisms, see Motion Perception.

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Basic Information

Motion Detection refers to technology and processes that can detect or identify movement or moving objects.

Applications for motion detection technology:

Simple Mechanical Methods

Things a spy might improvise in the field:

  • Tripwire - may be observed later to tell if an intruder has been here
  • Tripwire with alarm - a tripwire that sounds an alarm when tripped. Could be as simple as soda cans (with some rocks inside) tied to string.
  • A hair taped to the inside of a window sill - if the window is opened, the hair breaks free.
  • Very full glass of water - put on top of an object, if the object (or glass) is moved it'll spill.
  • Windchime or noisemaker on the back of a door - if the door is opened quickly, it'll make noise.

intermediate Methods

  • The "nightingale floor" - a Japanese favourite that consists of an expanse of deliberately squeaky floorboards.

Electronic Methods

See Also:


Game and Story Use

  • These may be hazards, traps, and alarms that the PCs have to overcome.
  • Alternately, the PCs may employ such devices for their own protection.
  • Each method has it's own advantages and drawbacks. Some are more easily defeated or triggered than others. Some only record what happened, others scare intruders off, warn authorities, or even take aggressive action.
  • The pet-immune sensors are a liability in a setting that has magic, demihumans or robots. Or, indeed, various species of animals such as monkeys and raccoons.
  • Likewise, passive infrared sensors are likely to be ineffective against anything close to ambient: undead, constructs, some robots…
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