| 摘要 |
A method of determining the location and status of a subject upon the occurrence of a trigger event comprises activating a sensor to a predetermined level corresponding to a class of event upon the occurrence of an event. An event signal is then transmitted to a central station indicating the class of event. Acknowledgement of receipt of signal is monitored and either acknowledgement of receipt signal is noted, or the event signal is retransmitted. Upon receipt of the acknowledgement signal, monitor mode is entered.
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