Theft protection system particularly for shop areas

Claim 1

A theft protection system, particularly for a shopping area, for recording the unauthorized removal of objects to which a preferably passive protection device is affixed having a resonance circuit tuned to a given frequency, through one of a number of exit passages each of which comprises an antenna system having a transmitting antenna for transmitting electro-magnetic interrogation signals of said given frequency and a receiving antenna for the resonance signals generated by the unauthorized removal of an object bearing a said resonance circuit through the passage, an alarm device being connected to a receiver connected with said receiving antenna to generate an alarm in response to reception of said resonance signal, said antenna systems for the exit passages being connected to a common transmitter and a common receiver through a transmitting multiplexer and a receiving multiplexer, a common control unit is connected to and controls said multiplexers, said transmitter and said receiver for sequential coupling of said antenna systems to said transmitter and said receiver in successive time frames for individual ones of said exit passages and actuation of said transmitter and said receiver in a sequence of transmitting and receiving intervals within each time frame, said control device being further connected to a number of separate alarm generators, one for each of said exit passages for actuating an alarm generator associated with a given exit passage in response to compliance with at least one alarm criterion associated with the transmitting and receiving intervals associated with the exit passage.

Claim 6

A system for detecting the presence of a control device of at least one of a plurality of locations, said system comprising: receiving antenna means at each of said plurality of locations for receiving an interrogation signal and in response thereto generating an electromagnetic field at a predetermined frequency; transmitter switching means coupled to each of said receiving antenna means for successively sending said interrogation signal to each respective receiving antenna means; transmitter means coupled to said transmitter switching means for providing said interrogation signal; transmitting antenna means at each of said plurality of locations for transmitting a response signal from said control device when said control device is within the electromagnetic field generated by said receiving antenna means; receiver switching means having a plurality of inputs coupled to respective said transmitting antenna means for receiving signals from said transmitting antenna means and passing selected ones of said signals to an output; receiver means coupled to said output of said receiver switching means for receiving the signals selected by said receiver switching means; alarm means at each of said plurality of locations for indicating when said control device is at a respective location; control means coupled to said receiver means, said receiver switching means, said transmitter means, said transmitting switching means and said alarm means for controlling the operation of said system, wherein said control means controls said transmitter switching means and said receiver switching means to successively connect each of said transmitting antenna means to said receiver means and its associated receiving antenna means to said transmitter means such that when said control device is within the electromagnetic field generated by one of said receiving antenna means, a responsive signal is received by said receiver from the associated transmitting antenna means, said responsive signal causing said control means to activate the associated said alarm means.

Claim 7

A system for detecting the presence of a control device of at least one of a plurality of locations, said system comprising: receiving antenna means at each of said plurality of locations for receiving an interrogation signal and in response thereto generating an electromagnetic field at a predetermined frequency; transmitter switching means coupled to each of said receiving antenna means for successively sending said interrogation signal to each respective receiving antenna means; transmitter means coupled to said transmitter switching means for providing said interrogation signal; transmitting antenna means at each of said plurality of locations for transmitting a response signal from said control device when said control device is within the electromagnetic field generated by said receiving antenna means; receiver switching means having a plurality of inputs coupled to respective said transmitting antenna means for receiving signals from said transmitting antenna means and passing selected ones of said signals to an output; receiver means coupled to said output of said receiver switching means for receiving the signals selected by said receiver switching means; alarm means at each of said plurality of locations for indicating when said control device is at a respective location; control means coupled to said receiver means, said receiver switching means, said transmitter means, said transmitting switching means and said alarm means for controlling the operation of said system, wherein said control means controls said transmitter switching means and said receiver switching means to successively connect each of said transmitting antenna means to said receiver means and its associated receiving antenna means to said transmitter means such that when said control device is within the electromagnetic field generated by one of said receiving antenna means, a responsive signal is received by said receiver from the associated transmitting antenna means, said responsive signal causing said control means to activate the associated said alarm means.