Emitters are security measures which emit laser beams. Depending on the type of Emitter, it is either impossible for an agent to walk onto a tile crossed by the beam, or there is a penalty for doing so (even if the agent is disguised, for example by Prism's Holo Projection Mesh). The type of Emitter(s) which appear in a facility depends on the corporation the facility belongs to.
Each Emitter is connected to a Power Supply which can be hacked or rebooted to disable or control the emitter. Emitters cannot be directly hacked as they do not have firewalls, but they can be rebooted using EMP Packs. Additionally, an enemy-controlled Emitter is always disabled when a guard is in the beam, even if the guard is knocked out or dead, or a drone under the agency's control.
Every facility has exactly one Emitter along a 2–4 tile boundary which connects two rooms, except for Security Dispatch missions and most Vault missions which have an additional Emitter protecting the objective room, and the Tutorial mission which has none. Except for Emitters protecting objective rooms, there is guaranteed to be an alternative route between two rooms connected by an Emitter which does not require disabling the Emitter or going through it.
While a Laser Panel is controlled by the enemy, it deactivates whenever a guard is in the beam, even when the guard is knocked out or dead. Otherwise, whenever the Laser Panel is enabled, whether controlled by the enemy or the agency, it deals lethal damage to any unit in the beam. In addition, if the beam deals lethal damage to an enemy unit while controlled by the agency, then the Laser Panel is rebooted for 6 turns.