A movable or removable seat for a motor vehicle is disclosed which preferably takes the form of a re-movable vehicle seat (1). The removable seat incorporates a first inductor (17) which forms part of an inductive coupling between the removable seat and a second inductor (21) which is mounted on the motor vehicle. The first inductor forms part of a resonant circuit which incorporates at least one capacitor. The resonant frequency of the resonant circuit is variable in response to a sensed parameter such as, for example, the position of a head-rest of the seat, the inclination of the back-rest of the seat and such like. A central unit (23) generates a square wave which excites the resonant circuit. A signal is transmitted from the resonant circuit to the central unit (23) which analyses the resonant frequency of the resonant circuit.