Abstract: A location system, for the tracking of personnel or products for establishing the location of an identification tag attached to a person or product, has the tag comprising a power source; an ultrasonic transducer; a transmitter connected to an output signal from the transducer and capable of transmitting multiple frequencies to establish the unique ID of the tag in question, including a first frequency solely to identify when a tag is about to start transmitting data; the system comprising further a plurality of strategically located ultrasonic receiver; and processing means including a reader incorporating a number of Goertzel filters corresponding to the number of frequencies transmitted to process output signals from the ultrasonic receivers to establish the ID of the read tag and its location.

Abstract: A location system, for the tracking of personnel or products for establishing the location of an identification tag attached to a person or product, has the tag comprising a power source; an ultrasonic transducer; a transmitter connected to an output signal from the transducer and capable of transmitting multiple frequencies to establish the unique ID of the tag in question, including a first frequency solely to identify when a tag is about to start transmitting data; the system comprising further a plurality of strategically located ultrasonic receiver; and processing means including a reader incorporating a number of Goertzel filters corresponding to the number of frequencies transmitted to process output signals from the ultrasonic receivers to establish the ID of the read tag and its location.