Patent ID: 7072671

Claim:
A radio system comprising at least one master station and a plurality of secondary stations, the master station having means for establishing a master log of time stamps of signals transmitted by active ones of the secondary stations and the active stations' identities, at least one of the secondary stations having means for establishing a log of time stamps of signals received from the active stations together with the received signals' measured quality and means for forwarding at least a portion of the log to the master station, the master station further comprising means for correlating the time stamps in a log forwarded to it with the time stamps in its master log in order to identify the active stations originating the signals received by the forwarded log's associated secondary station and for utilising the signal quality measurements in the forwarded log to determine the relative position of the associated secondary station, wherein the master log stores the relative locations of at least some of the active stations that are non-portable in the space being monitored and in that the position of a secondary station is indicated relative to at least one of the non-portable active stations.