Importance

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Abstract

A self-contained personal alarm device capable of signaling its location to a remote site such as a security station. The personal alarm device includes a housing enclosing a controller, an antenna, a cellular transmitter and a cellular receiver. The controller is coupled to the transmitter and receiver, which are in turn coupled to the antenna. The controller controls the transmitter and the receiver to receive position location signals such as Global Positioning System signals (GPS), establish a cellular connection with a remote site, and transmit device location data to the remote site on the cellular connection, wherein the device location data indicates the location of the device. The cellular connection is established via a cellular telecommunication network that includes an array of cell base stations. The GPS signals are transmitted to the device over the cellular network by providing each cell base station with a Differential Global Positioning System (DGPS) receiver. Using the DGPS receivers, GPS signals are repeated over the cellular network.

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First Claim