Patent ID: 6844816
Filing Date: 2005-01-18
Classification: G07C,G08B,H04L,H04M

Abstract:
1. A monitoring system for monitoring location of a person or thing to be monitored, comprising: a transmitter, associated with the person or thing to be monitored, for transmitting authentic signals at time intervals that vary according to a pattern and which include information representative of respective current positions where such authentic signals occur in said pattern of various time intervals in order to predict when a subsequent authentic signal from the transmitter is expected; and a receiver for receiving signals, said receiver being operative to use said current position information in a received authentic signal to identify a subsequent time interval from said pattern of various time intervals in order to predict when a subsequent authentic signal from the transmitter is expected, and, further, to determine whether an actual subsequently received signal is an authentic signal that is actually transmitted by said transmitter based on whether such subsequent signal is received when expected in the pattern of various time intervals.