Heartbeat Sensor



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 very similarly to the motion tracker in the Halo games. It displays the positions of people who are fairly close to and in front of the player. In 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 swap 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 block the sensor; only the perk Ninja can. 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. The Heartbeat Sensor will not detect enemies or friendlies after they have been killed.



Advantages

 * The Heartbeat Sensor allows the user to know where enemies are without the use of a UAV, making it valuable for certain stealth classes and setting up ambushes.
 * In Hardcore, where the mini-map is mostly disabled, the Heartbeat sensor will allow you to still find enemies before they see you.
 * It is especially effective for snipers to have this equipped as it can alert them to the danger of an approaching enemy (unless said enemy is equipped with the Ninja perk, the player is looking through the scope, or the enemy is directly behind the player).
 * The Heartbeat Sensor helps its user locate enemies through any obstructions, such as walls and smoke screens.
 * It's very helpful to use the Heartbeat Sensor in Search & Destroy due to the fact as you have one life each round.

Disadvantages

 * There is a somewhat long period of time (slightly longer than a UAV) between sweeps.
 * The sensor usually cannot be seen while using ADS (save for a small portion of the top of the screen) or while sprinting, however, a clicking sound will still alert the player if enemies are close by. However, some weapons (most notably the FAL) are near perfect with the sensor allowing you to still watch the sensor and aim down the sights.
 * When reloading a Grenade Launcher, the Sensor will obstruct the middle of the screen.
 * Enemies with Ninja will be able to easily surprise someone using the Heartbeat Sensor.
 * The sensor is almost useless in third-person multiplayer. This is because you cannot actually see the sensor itself in anyway, but you can still hear it beep. It is suggested that you use a different attachment because of this.
 * In single player, the display cannot be read while viewing through night vision goggles. The sensor will glow brightly making it impossible to see the reading.
 * The sensor only scans the area in front and to the sides of the player. Enemies behind the player cannot be detected unless they are directly behind the player.

Trivia

 * The Heartbeat Sensor cannot be folded back towards the gun in multiplayer.
 * The Heartbeat Sensor seems to have a smaller area of effect in multiplayer. This was done for balancing purposes.
 * The Heartbeat Sensor has a range of approximately 30 meters in singleplayer
 * The player will get a fuzzy screen when the enemy team uses an EMP.
 * There is a known glitch where if a player who is using the Ninja perk is killed by a player using a Heartbeat Sensor, the former player will show up on the killer's Heartbeat Sensor when watching the KillCam.
 * In campaign, an AA-12 with a heartbeat sensor can be used. The heartbeat sensor is not available in multiplayer on the AA-12 or any other secondary weapon.
 * In real life, there are actually devices that sense heartbeats, but they are larger than the one in MW2, about the size of a radar gun. As the game takes place in 2016, new advances to reduce size may have been made.
 * The Heartbeat Sensor is very hard to use in split-screen mode because the screen is smaller. Only about half of the screen may actually be seen, making the attachment an unwise choice for split-screen play.
 * When aiming down the sights with the TAR-21 with a Red Dot Sight, almost the entire heartbeat sensor screen is still visible.
 * Many players say they often end up watching the Heartbeat Sensor more than they actually look in front of themselves. This is counteracted by playing as though you don't have the Sensor until it detects an enemy and makes a ping, the pitch of which ascending as the enemy draws closer.
 * Some players choose not to use the Heartbeat Sensor due to the fact that it can be distracting at times, often leading to easily preventable deaths.
 * The heartbeat sensor is nearly identical to the "motion sensors" used in the movie Aliens, which are shown attached to the squads' weapons.
 * Heartbeat sensors are usually frowned upon in search and destroy because it removes the stealth from the game. As many players use the ninja perk in search and destroy, it is not recommended using a heartbeat sensor in search and destroy anyway.