Importance

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Abstract

A radio system and method for monitoring and locating objects, including individuals, animals and articles, both locally and on a nationwide scale use monitoring base stations communicating by ID code with portable transponders which are secured to the objects to be monitored. The transponder responds to signals transmitted by the base, the latter indicating by an alarm the absence of a timely appropriate response from the transponder. The base is capable of performing and participating in homing techniques to locate a lost transponder. A list of the IDs of all transponders reported missing is distributed from a central source by nationwide communication to a network of radio stations, each station broadcasting the list in an encoded signal in repetitive sequence along with regular programming. Cruising vehicles of public safety departments operating locally nationwide are equipped with automatic monitors for receiving specially coded messages including IDs from transponders within their areas. Each transponder, after failing to receive a signal from its base for a predetermined time period has the capability of scanning the band of the radio station network, locking onto the local station of the network and receiving its ID from the locked-on station when reported lost. Upon receipt of its ID from the locked-on station, the transponder initiates transmission of the specially coded message to make its presence known to the monitor of a local cruising vehicle and thereafter is capable of establishing communication with a local base for participation in local homing.

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First Claim