Personal alarm location system and method
First Claim
1. In a personal alarm location system having a plurality of locator units positioned at fixed positions and having a population of locatable units, a method of locating one of said locatable units, said method comprising steps of:
- transmitting a request signal from said one locatable unit;
receiving said request signal at a first group of said plurality of locator units;
measuring a power level for said request signal at each of said first group of locator units;
selecting a portion of said group of locator units in response to said power levels obtained in said measuring step; and
activating said selected portion of locator units to determine a position for said locatable unit.
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Accused Products
Abstract
A population of locatable personal detection units (PDUs) (20) are worn by users. Any number of locators (14) are placed at known locations within an area (10) where the users tend to be. When an alarm event for an individual user occurs, a request signal is transmitted from the user'"'"'s PDU (20). The request signal is received at several of the locators (14), each of which measure the power level of the request signal. A central computer (16) selects some of these locators (14) in response to the power level measurements. In sequence, the selected locators (14) transmit an interrogation signal to the PDU (20), the PDU (20) replies to the interrogation signal, and the locators (14) measure the duration transpiring between the interrogation and the reply. Based on the durations measured for at least three of the locators, the central computer (16) uses a multilateration process to localize the PDU (20).
120 Citations
30 Claims
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1. In a personal alarm location system having a plurality of locator units positioned at fixed positions and having a population of locatable units, a method of locating one of said locatable units, said method comprising steps of:
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transmitting a request signal from said one locatable unit; receiving said request signal at a first group of said plurality of locator units; measuring a power level for said request signal at each of said first group of locator units; selecting a portion of said group of locator units in response to said power levels obtained in said measuring step; and activating said selected portion of locator units to determine a position for said locatable unit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of operating a locatable unit in accordance with a personal alarm location system having a plurality of locator units positioned at fixed locations, said method comprising steps of:
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detecting an activation event; transmitting a request signal in response to said activation event; receiving a first interrogation signal; sending a first reply signal in response to said first interrogation signal, said reply signal being sent approximately a constant predetermined duration following said receiving step; receiving a second interrogation signal following said step of sending a first reply signal; and sending a second reply signal in response to said second interrogation signal said second reply signal being sent approximately said constant predetermined duration following said second interrogation signal receiving step. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A personal alarm location system operable over a predetermined area, said personal alarm system comprising:
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at least one locatable unit positioned in said area, said locatable unit being configured to transmit request and reply signals and to receive an interrogation signal; a plurality of locator units positioned at known places within said area, wherein each locator unit is configured to receive said request signal and said reply signal, to detect a power level at which said request signal is received, to send said interrogation signal and to measure the duration between the sending of said interrogation signal and the detecting of said reply signal; and a central controller in data communication with each of said locator units, said central controller being configured to instruct selected ones of said locator units to send said interrogation signal, said selected ones of said locator units being selected in response to request signal power levels detected at said selected ones of said locator units. - View Dependent Claims (25, 26, 27, 28, 29, 30)
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Specification