Beacon tower

Promotional image for Halo: Reach Noble Map Pack featuring the multiplayer map Tempest. From the Halo: Reach press kit.

A beam emitter as a part of a Halo ring's weather control system.

A beam emitter is a Forerunner device or a structure that, as the name implies, emits beams of energy. Though applied for many purposes, they are generally used to transport enormous amounts of energy from one place to another, serving as sophisticated power conduits. The beams may be constant, feeding a steady stream of energy to a certain system such as an energy barrier, or momentarily channel the energy required in the activation of an installation.

Types

File:Scrn 009.jpg

A beam emitter tower on Alpha Halo.

Beam emitters are often incorporated in large delta-shaped structures with a cleave down the approximate center. They fire beams upwards, in the case of the Halo installations to the center, and in the case of the Ark up into space.^[1] The exact function of these machines is unknown, but they may be used to transport energy for the activation process of the Halo rings or used to get rid of excess energy. It is also possible that the beams seen on Installation 04 are simulated firings of the ring.

The Control Rooms of the Halo installations also possess a type of beam emitter, which fires a continuous beam from the depths of the Control Room to the top of the structure, and into the center of the ring when the Installation is activated.^[1] In case the firing sequence is canceled, like on Delta Halo, the beam collects into a large bolt of energy, which is then fired into the center of the ring.^[2]

The Ark Portal in Kenya also has a type of beam emitter, which discharges a concentrated beam to the sky when the portal is activated.^[3] In addition, Apex site of the Unnamed Shield World also possessed a beam emitter. Continuous beams of energy are also channeled through the Phase Pulse Generators used to control the firing systems of the Halo rings.^[4] In High Charity, the Covenant used a conduit of energy to connect the Forerunner Dreadnought's engines into the city's power grid.^[5]

Around Installation 00's Citadel, three Barrier Towers featuring beam emitter towers are used to project an energy barrier that surrounds the Citadel.^[6] The weather control systems on the Halo rings also feature beam emitters.^[7]

Trivia

If you manage to stand at the top of the chute in which the beam shoots from, the beam can either kill you, sending you over a hundred feet in the air, or completely pass through you. When you are killed by the beam, it will say "(Player) was killed by the Guardians".
In Halo PC, the beams coming from the beam emitters will most likely kill you if you are hit by one. However, in Halo 3, the beams coming from the beam emitters (except in Valhalla) will not kill you, no matter what. This is most likely due to gameplay reasons.