The movable device includes a detector for detecting that an object is located in the vicinity of or at the movable device, as well as a transmitter module for transmitting two signals having different signals speeds. These two signals are received by a receiver, the receiver having a detector to ascertain whether the second signal arrives within a predetermined time period as of reception of the first signal, so as to provide, when this has been detected, a detector signal indicating that the movable device has been contacted by the object. Exemplary movable devices are game devices such as footballs. Exemplary objects are arms, legs, football shoes, rackets, bats, etc.