A system and method for surveillance of a physical environment. May utilise already installed equipment, such as WLAN for surveillance purposes. This makes the system cost effective to implement. Transmits a first and a second signal. The signals are received by receivers, and the received signals are compared in order to detect a difference in the signals, the difference being caused by a physical change present in the signal path between transmitter(s) and receiver(s). Does not require high spectral purity of the transmitted signals or heavy computations in order to establish that a change has occurred. Suitable for intruder alarm purposes.
|IPC||G01V3/12; G08B13/24; G08B25/08; (IPC1-7): G08B13/00|
|Priority number||US20030602921 20030625|
|Publication status||Published - 29 Apr 2004|