Phoenix Logs/UNSC Buildings/Turret
From Halopedia, the Halo wiki
Automated weapon towers are installed around UNSC firebases to deter attack. Most firebase facilities have power and control hookups prearranged for up to four Turrets. Turrets can engage a variety of targets, but each can be upgraded to specialize against one particular threat: aircraft. vehicle, or infantry.
The base towers used by the Spirit of Fire are relics of a defensive-in-depth tactical doctrine the UNSC was eventually forced to abandon as the Covenant War ground down Humanity's armies and industrial centers. Turrets are still invaluable tools for the field commander's arsenal on the Ark, however, freeing up troops and vehicles needed to find. fix, and destroy the Banished.