A sensor is any object which can detect the presence of an enemy player or object. There are many different types of sensors that have different methods of detection. The combination of all of your team's sensors is referred to as your sensor network. Your sensor network, as well as all players and objects currently being detected by your sensor network, can be viewed by accessing the command circuit. The red triangle that appears over the heads of enemy players is also dependent on your sensor network. The red triangle will only appear if that enemy player is being detected by some form of sensor in your sensor network.
Pulse sensor
A pulse sensor is a base asset that detects enemy players and vehicles when they come into range. Pulse sensors have a detection range and will detect anything inside that range so long it is not obstructed. The detection field of a pulse sensor cannot penetrate mountains, hills, or any structures. There are two types of pulse sensor base assets. One is referred to as a large pulse sensor, and the other is a medium pulse sensor. Just as it sounds, large pulse sensors appear taller and have a much wider detection field range. Pulse sensors will spin around when they are active. If a pulse sensor takes too much damage or is not powered, it will be inactive and will be unable to detect anything. Additionally, all base turrets and deployable turrets have a built-in pulse sensor - except for the sentry turret, which has a motion sensor instead.
Deployable pulse sensor
Additionally, there is a deployable pack known as deployable pulse sensor, which acts exactly like a regular pulse sensor, but with a much smaller range. These are definitely useful, as you can often hide them along enemy cap routes and other routes, allowing you to detect incoming enemies much sooner than you otherwise would. They can also be used along with turrets and motion sensors to remove the vulnerability of standing still and shooting at the target. Even so, most teams rarely find the time to set up deployable pulse sensors. While they are beneficial, the time and effort to deploy them might not always be worth it. To deploy a pulse sensor, you need to acquire one from an inventory station and then press the Use Pack key when aiming at the desired location. Deployable pulse sensors can only be deployed on floors and terrain that is not too steep.
Motion sensor
A motion sensor is a sensor that detects anything that moves within its detection field range. If the object stops moving, then the motion sensor stops detecting it. There are only two types of motion sensors in most mods. One is the motion sensor that is built into every sentry turret, and the other is the deployable motion sensor pack. To deploy a motion sensor, you need to acquire one from an inventory station and then press the Use Pack key when aiming at the desired location. The only reason to use a motion sensor is they are the only sensor that can detect cloaked players. Motion sensors can be deployed on walls and ceilings in addition to floors and terrain.
Camera
The camera is a deployable which occupies the grenade slot. They are often used as short-range sensors instead of their originally intended use of looking out of. In Classic, they are often used to detect users with a sensor jammer and are often put close to turrets. In addition to being detectors, they can also provide a ledge for players to stand on or to place satchel charges on. They can be controlled via the command circuit. Unlike most deployables, cameras are thrown with the Throw Grenade key (G by default) instead of placed.
Player vision
Visual detection by players will show enemies on the sensor network unless they are using a sensor jammer or are actively cloaked. Looking at someone will allow your entire team to see that player's IFF, while looking at enemy assets will make them show up on the command circuit. Visual detection nullifies the cloak pack's passive jamming abilities, allowing turrets to target said player.