Patent ID: 6181253
Filing Date: 2001-01-30
Classification: G08B

Abstract:
A method for monitoring the location of a monitored person (MP) with reference to a permitted site, the method comprising the steps of:(1) designating a site, having a connected and closed curve or surface of arbitrary shape as a site boundary, as a permitted site;(2) permitting an MP to move on the permitted site;(3) receiving location determination (LD) signals at an LD unit attached to the MP that allow determination of the present location of the MP;(4) determining the present location of the MP, using the LD unit;(5) when the MP is not on the permitted site at one or more of the location determination times, transmitting an alarm signal number 1;(6) providing a signal generator that is attached to the MP's body and that, when activated, transmits a distinguishable electromagnetic signal;(7) providing the MP with a motion sensor that, when the sensor is substantially motionless, issues a stationarity signal;(8) when the MP is on the permitted site:(8A) determining whether the LD unit is receiving LD signals;(8B) when the LD unit is receiving LD signals, returning to step (4), and when the LD unit is not receiving LD signals, proceeding to step (8C);(8C) issuing an advisory signal number 1 and causing a first timer to begin a countdown from an initial time .DELTA.t1=.DELTA.t1, max;(8D) determining whether the motion sensor is issuing a stationarity signal;(8E) when the first timer reaches the maximum accumulated time .DELTA.t1=.DELTA.t1, max and the motion sensor has not yet begun issuing a stationarity signal, transmitting an alarm signal number 2 and returning to step (8A);(8F) when the motion sensor begins issuing a stationarity signal before the first timer reaches the maximum accumulated time .DELTA.t1=.DELTA.t1, max deactivating the LD unit, deactivating the first timer, resetting the first timer accumulated time to .DELTA.t1=0, activating the signal generator and causing the signal generator to transmit a distinguishable signal;(8G) providing a signal sensor, positioned at a selected location, that receives the distinguishable signal from the activated signal generator and that assigns a range attribute value A, having a real number value, to the received signal that is an approximate measure of the distance between the signal generator and the signal sensor;(8H) determining whether the range attribute value A for the distinguishable signal, received from the signal generator, is less than a selected range attribute threshold value A.sub.thr, at a sequence of at least two times;(8I) when A.gtoreq.A.sub.thr, continuing to compare the range attribute value A with the threshold value A.sub.thr and(8J) when A<A.sub.thr(8J-1) transmitting an advisory signal number 2 and causing a second timer to begin a second countdown from a time .DELTA.t2=0 to a second selected maximum accumulated countdown time of .DELTA.t2=.DELTA.t2, max;(8J-2) when the second countdown has begun, the motion sensor is issuing a stationarity signal, and .DELTA.t2<.DELTA.t2, max continuing to compare the range attribute value A with the threshold value A.sub.thr ;(8J-3) when the second countdown has begun, the motion sensor is issuing a stationarity signal, and .DELTA.t2<.DELTA.t2, max transmitting an alarm signal number 3, returning to step (8H);(8J-4) when the second countdown has begun and the motion sensor is not issuing a stationarity signal, deactivating the second timer and resetting the second timer accumulated time to .DELTA.t2=0;(8J-5) when the second countdown has begun and the motion sensor is not issuing a stationarity signal, activating the LD unit and causing a third timer to begin a countdown from an initial time .DELTA.t3=0 to a third selected maximum accumulated countdown time .DELTA.t3=.DELTA.t3, max;(8J-6) when the second countdown has begun, the motion sensor is not issuing a stationarity signal and .DELTA.t3.ltoreq..DELTA.t3, max determining if the LD unit has acquired LD signals;(8J-7) when the second countdown has begun, the motion sensor is not issuing a stationarity signal and .DELTA.t3.ltoreq..DELTA.t3, max and the LD unit has acquired LD signals, initializing and deactivating the third timer and returning to step (8A);(8J-8) when the second countdown has begun, the motion sensor is not issuing a stationarity signal and .DELTA.t3.ltoreq..DELTA.t3, max, and the LD unit has not acquired LD signals, returning to step (8J-6)]; and(8J-9) when the second countdown has begun, the motion sensor is not issuing a stationarity signal and .DELTA.t3.ltoreq..DELTA.t3, max and the LD unit has not acquired LD signals, deactivating and initializing the third time counter, transmitting an alarm signal number 4 and returning to step (8A).