Controlling the function of a mobile device with a retractable cord

A mobile device, particularly a wireless headset 10, includes a cord 12 to which an earpiece 11 is fixed and a module 13 having a spring-actuated retractor reel 30 into which the cord 12 is retracted. A fastener 15 on the module 13 makes the device wearable. A rotary encoder generates a position data output according to the rotational position of the reel 30, and a controller receives the position data output from the sensor, and, in response, controls a function such as placing the device in an on-hook or off-hook state. The retractor may comprise a ratchet and pawl arrangement (37,38 - figure 4) and slip rings (29a, 29b) may be used to transmit audio signals to the cord. The rotary encoder may comprise a discontinuity in a circumferential surface of the reel which may be sensed by a Hall-effect sensor as the reel rotates. At least one of the discontinuities may comprise a recessed area (36) formed in one of the slip rings.