Radar jammer

The Radar Jammer is an equipment item in Halo 3 that scrambles nearby players motion sensors by creating a multitude of false dots on the enemy radar. While it can create chaos for enemies, it also has the same effect on teammates. In campaign mode it is uncommon for one to be dropped by enemy brutes. It is mostly used by brute stalkers to disorient and confuse their prey. It is no longer available in matchmaking since in the case of the Flare and the Radar Jammer, those objects had physics properties that allowed players do things they shouldn't have been doing.

If anyone knows they're under the effect of it, it is possible to detect the false and real enemy (Dots from the jammer almost never stop whereas enemy tend to move more carefully and stop at points, taking the red dot off your tracker, also the fake blips seem to move faster and more "fluid" than a normal person.) An activated Radar Jammer can also be destroyed by weapons fire.

The Radar Jammer is similar in appearance to the Power Drain and Flare, except for a red glow instead of blue or yellow. Its symbol in the HUD is a dot with curved waves emitting from it.

some even say thanks to the radar jammer comes ghost like the ghost of foundry,ghost of rat's nest,entc....

Multiplayer Tactics
but still try not to run horizontal to the player else he maybe can see you on the radar
 * The Radar Jammer is best used in conjunction with the Active Camouflage power-up. When it is deployed, the enemy will be distracted enough that the player may be able to score a quick melee kill, or an assassination.(Sometimes)
 * This type of equipment is both useful and detrimental to the user, his allies, and the enemy, since everyone's motion sensors are affected. The jammer should only be used if the player is in a position where he or she does not need to use his motion sensor to score a kill.
 * Watch out for other players throwing these at you. If this happens nothing annoys them more than shooting the jammer before it hits the ground and making it explode in their faces. This is also useful in the campaign against brutes.
 * As the Bubble Shield and the Power Drain are parallel to one another in use, the Radar Jammer and Active Camouflage are adjacent in usage as well.
 * In CTF, using this together with the Flare can be useful. Have one player throw in the Radar Jammer, then throw in the Flare, while looking at the Flag so you know what way to go. By the time your opponents can see again, they'll see their flag is gone. If Flares aren't available, use an Active Camo instead. Fun to watch, fun to do.

Trivia

 * For a time, the Radar Jammer appeared on several maps in Halo 3 Matchmaking. But as of December 1, 2007, the Radar Jammer, along with the flare, has been removed, due to a glitch that allows the player to jump high enough to get to certain hiding spots that would have otherwise been out of reach.
 * When the player deploys a Radar Jammer in Campaign mode, Brutes will sometimes become confused and look around distractedly.
 * If the player is seen by a Brute or a Grunt when deploying the Radar Jammer, the Brutes may occasionally go berserk; Grunts will sometimes panic.
 * Red radar "blips" generated by the Radar Jammer will move much faster on your motion tracker screen than those generated by an enemy.
 * The Radar Jammer is not useful if you deploy it when trying to find an enemy. It only makes it tougher to find them (unless in plain sight).