TR/9 trip mine

The TR/9 Antipersonnel Mine, otherwise known as the Trip Mine, is a UNSC equipment item in Halo 3.

Overview
The trip mine is activated by proximity or touch. Once deployed, it can be identified by a high pitched beeping noise and a distinctive flashing orange light on its top. Its blast radius is considerably larger than a grenade explosion or rocket explosion allowing vehicles to be thrown into the air. The trip mine can not be deactivated once deployed. It will explode after about ninety seconds if nothing triggers it. However, it can be remotely activated by projectile weapons or grenade explosions. The Trip Mine, while having a larger blast radius than a Frag Grenade, will only slightly injure a Spartan or Elite. It will, however, kill Brutes and unwary Marines. The Trip Mine only spawns by default on Sandtrap and Rat's Nest. Destroying an enemy vehicle with the TR/9 in Campaign or Multiplayer will unlock the Achievement We're In For Some Chop. Brutes may sometimes deploy Trip Mines.

Tactics

 * When running away from a moving vehicle, a mine can be deployed in front of a moving enemy vehicle. Be careful though, it may kill not only the driver and passengers, but you as well.
 * Try to combine the powers of different pieces of equipment to make interesting effects. For example, its fun to drop a trip mine into an enemy Bubble Shield. The Bubble Shield then turns into a "bubble of death".
 * If you deploy a trip mine on top of a Man Cannon, the mine will go flying out into the battle field. Throughout the beta, the trip mine would sometimes disappear entirely when thrown into the Man Cannon. It would still explode if someone or something were to go within the activation radius.
 * One of the most evil tricks, as Bungie mentioned before, is to deploy a mine in the exact position where it spawns. Some players will notice that the mine is armed (by listening to its distinct audio and visual cues), but most players will attempt to collect it, resulting a kill which would certainly not have happened if the player is attentive.
 * Trip Mines are the only equipment currently in multiplayer that directly kill enemies.
 * The Trip Mine logo, along with the Bubble Shield logo, is a Halo 3 emblem.
 * Try throwing a frag at a trip mine for extra damage.
 * Another trick with the Trip Mine is if you crouch and walk over it it will not explode.

Disadvantages

 * Sometimes while playing in multiplayer or campaign you can accidently run or drive over your own trip mines.
 * Players can also be clever and use their enemy's trip mines against them by luring them onto trip mines.
 * Trip mines are ultra sensitive so when you move away don't go forward again.
 * It is easy for a enemy to see a Trip Mine that you have deployed, due to it's glow.

Trivia

 * It was hypothesized that the Trip Mine may be the Lotus Anti Tank Mine, or they may be both made by the same manufacturer. This is unlikely, though, as a Scorpion Tank can easily drive over a Trip Mine and survive.
 * The trip mine is used to get the "we're in for some chop" achievement.
 * A Trip Mine will not explode if you crouch-walk over it.