Separation determination systems for determining the separation between a base station and a transponder, whereby the base station includes an oscillating signal source, for generating a signal and a transmission device for broadcasting the signal. The transponder includes a receiving device, for receiving the signal from the base station, an oscillator, for generating a signal which is phase-coherent therewith and a transmission device for broadcasting the phase-coherent signal. The base station furthermore includes a receiver device, for receiving the phase-coherent signal from the transponder and a separation determination device for determining the distance between base station and transponder. The system and components may be improved whereby the oscillator in the transponder is energized with the received signal in order to generate a quasi-phase-coherent signal.