An appliance

A device 10 includes a main unit 12 to which one of a plurality of attachments (14, 16, fig.5) is attachable, a capacitance sensor 34, and a control module 28 operable to determine which of the plurality of attachments is attached to the main unit based on data output by the capacitance sensor. Device temperature or fan speed may be controlled based on the detected attachment. The main unit has one or plural electrodes 30 arranged around a bore 44 of the device. Each attachment has electrodes extending for different lengths around regions which attach to the main unit (fig.6), which produce different capacitance readings for each attachment. Alternatively or additionally a dielectric (256, 258, fig.10) on the attachments may vary in thickness between them. In another embodiment attachment electrodes interfere to different extents with an electromagnetic field generated by electrodes in the main unit (fig. 12) to alter a capacitance measurement. Applications include hair dryers, vacuum cleaners and power tools.