Call Of Duty : Modern Warfare 2
The Heartbeat Sensor is an attachment used in Call of Duty: Modern Warfare 2. The attachment allows the user to track multiple targets, somewhat like UAV and similarly to the motion trackers in the Halo games (though the latter is a 360 degrees detector with immediate update, built into the armor) and notably, to the motion tracker in the Aliens movie (despite it is not a separate piece of equipment). It displays the positions of people who are fairly close to and in front of the player. In the campaign, the display screen can be folded out from the side of the weapon and folded back in again. The first time it is used is in the level Cliffhanger, where Roach finds himself in near white-out conditions. It is used also in the level Just Like Old Times if the player as Soap swaps his weapon to the Silenced ACR. The sensor uses some kind of IFF system to tell the difference between friendlies and enemies. Friendlies are blue dots and enemies are white. In multiplayer games, friendlies appear as green dots instead of blue and enemies appear as red dots instead of white. The new version of UAV jammer, Cold-Blooded, cannot bypass the sensor; only the perk Ninja can. The EMP killstreak will render it inoperative for the duration of the killstreak, however, so that only static can be seen on the screen. This attachment is compatible with assault rifles, light machine guns, and sniper rifles. It is also seen on the AA-12 in a few Special Ops missions such as Acceptable Losses. To unlock the Heartbeat Sensor the player must get 15 suppressed kills with the weapon. This is probably easiest to achieve in Hardcore mode as all silenced primary weapons kill in at most 2 shots even without Stopping Power in this mode.