A protocol droid was a type of droid designed to assist sentients in their relations with one another and were programmed mostly for etiquette, and were often used as translators between sentients or between sentients and computers.
They also possessed knowledge about various cultures and customs, in order to advise those for whom they are working, and also so that they themselves may behave in a diplomatic and culturally sensitive manner.
Protocol droids constructed around 4,000 BBY (around the time of the Great Sith War and the Jedi Civil War) were frequently engineered with certain situational and behavioral shifts set to occur whenever another design-generation was reached. A number of these droids underwent radical changes with each new generation—for example, when a C7-model droid supplanted the C6 variety. Each numeric "jump" in sequence could have had wide-ranging changes in functionality and temperament during that historical period.
Cybot Galactica, the most famous and successful manufacturer of protocol droids, outfited them with SyntheTech AA-1 VerboBrains to give protocol droids personalities with emotions and the ability to learn and grow very similar to organic beings. The 3PO unit possessed a TranLang III Communications device that could reproduce over six million languages, as well as reproduce any sound it picked up. Some models, such as the pricey E-3POs, also included the TechSpan I module, making it possible to interface with Imperial networks and undocumented technologies of Imperial subcontractors. To date, there are very few feminine-programmed protocol droids.
- 3DO Protocol/Service Droid; manufactured by Duwani Mechanical Products
- 3PO-series protocol droid; manufactured by Cybot Galactica
- 5YQ-series protocol droid; manufactured by Cybot Galactica
- B-1 series protocol droid
- CZ-series communications/business droid; manufactured by Serv-O-Droid, Inc.
- GE3-series protocol droid; manufactured by Czerka Corporation
- LOM-series protocol droid; manufactured by Industrial Automaton
- M-3PO military protocol droid; manufactured by Cybot Galactica
- Orbot protocol droid; manufactured by Serv-O-Droid, Inc.
- RA-7 protocol droid; manufactured by Arakyd Industries
- Registration protocol droid
- TC-series protocol droid; manufactured by Cybot Galactica