TR/9 trip mine

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

Background
The trip mine can be activated by proximity or touch, but will not be activated by a crouched player. Once deployed, it can be identified by a high pitched beeping noise or by a distinctive flashing red light on its top. Its blast radius is considerably larger than a grenade explosion or rocket explosion allowing vehicles to be deployed into the air. It can be attached to vehicles and other objects and is often used to guard entrances. The activation radius is smaller than the kill radius. The trip mine can not be deactivated once deployed. However, it can be remotely activated by projectile weapons or grenade explosions.

During the Halo 3 Beta, the mine did not have an up or down. In the Halo 3 if placed upside down it will detonate automatically.

In the final version of the game, a Trip Mine will NOT kill a fully shielded Spartan or Elite, nor will it destroy vehicles in one blast. It has been significantly weakened from the beta, and it does not, by default, spawn on any maps in Matchmaking, save Sandtrap, which is only in Social games. This can make it frustrating to get the "We're in for some chop" achievement, as it can only be achieved now in the campaign.



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.
 * If you deploy a trip mine on top of a Man Cannon, the mine will go flying out into the battle field. Though on 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.
 * Also deploying the mine in the general area where the Man Cannon deposits players will kill the next person to man cannon from the base. Don't do it to your own base if your intentions aren't being a team killer.
 * Putting a trip mine in front of an unmanned vehicle will result in a nasty surprise to the next one entering it.
 * Place them in areas that are hard to see and that players need to go. A perfect example is in front of the Man Cannon. There is a downward incline before the Man cannon. Placing one here makes it unnoticeable to the player entering the Man Cannon. Be careful or the trip mine may be launched by accident.
 * Be sure to inform your teammates of the locations of trip mines. Otherwise, you may get a betrayal if a teammate steps on it.
 * In Forge trip mines can be deployed as a defensive "wall" for tight choke points.