Acoustic signallers were components which could be installed into droids. The droid HURID-327 was equipped with a binary acoustic signaller.
Acoustic signallers were first mentioned in Galaxy Guide 7: Mos Eisley, a Star Wars Legends supplement for Star Wars: The Roleplaying Game, written by Martin Wixted and released in 1993. They were confirmed to be canon by the reference book Star Wars: The Force Awakens: The Visual Dictionary, which was written by Pablo Hidalgo and released in 2015.
- Star Wars: The Force Awakens: The Visual Dictionary
- Star Wars: Build Your Own R2-D2 1
- Star Wars: The Complete Visual Dictionary, New Edition