An assembly and a method for determining a change in capacitance in a cable, such as a change caused by a deformation of the cable. The deformation may be caused by a deforming element attached to the cable and slideable along the cable. The deforming element may be adapted to be compressed by a user and convert the compression force into a compression of the cable so as to cause the capacitance change. The assembly may form part of a headset and the deformation may be used to control a media player or mobile telephone used with the headset.