They are employed by technologically advanced organizations, such as the Enclave, or the Brotherhood of Steel, and historic sites for security detail, such as the Museum of History, though in the latter case their former operators had been long since dead. In one case, a raider gang near the Arlington Library has reprogrammed turrets to protect their camp and chem lab.
Automated turrets can either be mounted to the ceiling or the floor. Those mounted on the ceiling fire conventional ammunition at an automatic rate, whereas floor mounted turrets fire laser beams similar to the laser rifle but in a faster succession. Both varieties have unlimited ammunition. As a rule, odd numbered turrets use conventional bullets and even numbered turrets use laser projectiles.
Automated turrets are often found in military installations or areas of historical value. Although not too damaging at lower levels, they can be quite deadly if they surprise you, or if they are in groups. Both types of turrets can be frenzied by shooting either the targeting chip (on ground units) or the lens (on ceiling units). Once frenzied, similar to insects and robots, the turrets will fire on everything they see. All turrets can be shut down using the Robotics Expert perk if you can reach them unnoticed while sneaking.
Alien turrets are always ceiling-mounted and can be harder to see due to their much smaller size. They shoot energy beams similar to the alien atomizer and disintegrator in rapid salvos of five shots. The individual pulses aren't highly damaging, but can take a chunk out of the player's health if the Lone Wanderer gets caught out in the open for too long.
While they cannot be shut down or frenzied via terminal, it is possible to remotely detonate them using nearby switches aboard the Mothership. They explode in a blast of green plasma, similar to a plasma grenade. Like normal turrets, they are unable to shoot directly below them and can be shut down using the Robotics Expert perk if you are able to reach them by jumping while crouched.
These can be found in buildings and on bridges and ceilings. A couple are found at Fort Independence. These turrets are often used by organizations such as the Brotherhood Outcasts, but can be found widely across the wasteland. Even raiders use them as sentries. They can be frenzied just like any other turret when the player cripples the lens.
These turrets can be found inside, and in front of, buildings, as well as on bridges. All floor-mounted models have laser weaponry and can be frenzied when their targeting chip is destroyed. Some can be found outside the Citadel.
Turrets are generally controlled from a nearby terminal. Using your science skill to hack the terminal will allow you to reprogram the targeting parameters, which will allow you to either reset its targeting parameters, causing it to target any character (not just the player, similar to the frenzy effect), or shut it down completely. After being turned off, the turret can be turned back on at the same terminal if so desired.
The ceiling-based turrets have a blind spot directly below them where they cannot attack. They also rotate rather slowly following a mark, so can be outrun or circle-strafed at close distance.
With the Robotics Expert perk it is possible to sneak up on turrets and disable them, as long as you can reach them. You don't necessarily need to be hidden, simply being momentarily out of sight is enough to deactivate them.
Turrets, like eyebots, cannot be looted for scrap metal when killed, as they either explode into small pieces, or disappear altogether. However, sometimes floor-mounted turrets will not explode, yielding some scrap metal.