- "I've designed this tracking device. You just set it to search for a moving object so. Hasn't got much of a range, but when you get within a certain distance it will start to give of a signal."
"What's it key on?"
"Micro changes in air density."
- ―Ash and Ripley regarding the tracking device (from Alien)
The tracking device keyed on micro changes in air density. When motion is detected within a certain distance the device will begin to give of a signal. However, the range at which the device could detect movement was short.
Behind the ScenesEdit
The motion tracker from Alien designed by Ash to locate the Alien was built by Ron Cobb. The prop features colored lights, a small television viewer, and a sound output to indicate detected movement. An ice cube tray is also visible as part of the device's surface detail.
The small television viewer was a Panasonic Ranger 505 portable TV which various cosmetics were added including an ice cube tray (left side) and a gully cover (right side).
At least two props of the tracker were made for Alien with one currently owned by collector Bob Burns. The tracker owned by Bob Burns is not complete. Parts missing from Burns' include the tube that starts to the right of the gully cover and runs in front of the weapon, connecting with the front end of the handle.
- After the events of Alien, all known tracking devices were destroyed when the Nostromo exploded.
- When the trackers are first introduced in the film, they emit a high-pitched humming when they register movement, as heard when they are first tested and when Ripley, Parker and Brett mistakenly detect Jones. However, when Dallas is in the air shafts, the devices instead issue a completely different beeping tone.
- The tracking device from Alien was likely the inspiration for the M314 Motion Tracker seen in Aliens.
- The Aliens: Colonial Marines DLC map Nostromo has two tracking devices on the cafeteria table.
- Aliens: Colonial Marines (video game, multiplayer only)