Method and apparatus for determining a position of a transmitter in three dimensions

The invention relates to a method and an apparatus for determining a position of a transmitter in three dimensions. Such position determination is required, for example, for an access and operation authorization system which is referred to by the expression a "hands free" system. In order to determine a position of a transmitter in three dimensions, a signal transmitted by the transmitter is received by four receivers that are separated from one another in three dimensions and are not all disposed on the same plane. In which case the time intervals between a reception of the signal by the four receivers are used to determine the position of the transmitter, taking into account the configuration of the receivers and a propagation speed of the signal in space.