Created by the RobCo Industries, protectron robots were designed (as their name suggests) for protection, although they can also be seen being used in a manual labor role as well. Typically used in office-type settings, their secondary programming is modular, making them useful as greeters, ticket collectors, bartenders, celebrity or historical figure impersonators, even sexual partners. In terms of combat, protectrons are usually weak and easy to defeat, because of their weak weapons and slow movement speed.
Some attributes of the protectrons looks were derived from 1950's comic books, the era in which many of Fallout's designs come from.
Many protectrons were commissioned by the U.S. Army before the Great War of 2077. They are painted a dark olive drab with a white star on their chest. These mechanized soldiers still wander the wastes, attacking everything from radroaches to Brotherhood Outcasts. Interestingly, the Brotherhood Outcasts use their own protectrons which are painted in rust and black. The Pitt adds a new variety of protectron called the "factory protectron", which lacks a glass dome but possesses a single ocular lens, and a cage around the combat inhibitor. The top of where the dome would be appears to be made to look like a construction hard-hat and the body has a yellow coloration. Broken Steel adds "Enclave protectrons", which appear to be much newer, with red glass domes and a polished steel-gray finish. A special red-painted protectron appears at the House of Wares in Point Lookout.
Protectrons in various areas have been programmed differently; the protectrons in the Nuka-Cola plant for example, say that they are operating under the authority of the Nuka-Cola Corporation as they attack you, with the words "Nuka-Cola!" being dubbed in from an exterior source. Other protectrons have even been supplied with sophisticated personalities, such as Button Gwinnett and Dean Dewey.
A protectron with the basic personality loaded can execute "sequences", lists of tasks to complete, such as patrolling an area for intruders or scanning passengers for tickets, in the case of the metro station protectrons. Some sequences may have been programmed by RobCo Industries, while others were written by robotics technicians at the locations where they are used. When not in use, a protectron unit is stored in a base pod, which also charges its battery. The protectron is connected to its base pod via radio uplink, and the pod is in turn linked to a control terminal or computer system, which can be hacked to release the protectron from stasis.