The droid detector at Chalmun's Cantina
Detectors for droids were specialized pieces of equipment designed to sense the existence of droids. Wuher, who worked as a bartender, possessed one of these detectors; it was installed within Chalmun's Spaceport Cantina. The device failed to function correctly when Luke Skywalker came to the cantina alongside the droids C-3PO and R2-D2, so it did not warn him about their arrival.