Gary T Carroll, George J Pilmanis, Vincent D Stinton: Adaptable electronic monitoring and identification system. B I Incorporated, Fitch Even Tabin & Flannery, August 28, 1990: US04952928 (517 worldwide citation)

A personnel monitoring system includes a transmitting or transponding unit that is worn or carried by the individual being monitored. This transmitting or transponder unit periodically, or upon request, transmits a uniquely encoded signal that identifies the person being monitored, as well as inform ...