in an ac magnetic tracker one or more multi - axis field sources , each operating at a different frequency , or frequency set , are detected and tracked in three - dimensional space , even when wireless or otherwise not physically connected to the tracking system . multiple sources can be tracked simultaneously as they each operate with their own unique detectable set of parameters . the invention not only provides the ability to uniquely identify one or more sources by their frequencies , but also to synchronize with these frequencies in order to measure signals that then allow tracking the position and orientation of the source . further , these sources need not be present at the time of system start - up but can come and go while being detected , discriminated and tracked . it also should be noted that application of such systems in multiples with more sensors not synchronized to a source or sources also could be employed to give the reverse appearance of a known source phase and incoherency with the sensors .