means for transmitting into or through the surveillance zone electromagnetic energy at or near the resonant frequency of the security tag 20 and means for detecting a field disturbance that the presence of an active resonant circuit security tag causes thereby establishing the presence of a security tag 20 and thus a protected article within the surveillance zone the resonant circuit 15 may comprise one or more inductive elements electrically connected to one or more capacitive elements in a preferred embodiment the resonant circuit is formed by the combination of a single inductive element l electrically connected with a single capacitive element or capacitance c in a series loop however multiple inductor and capacitor elements could alternatively be employed the size of the inductor l and the value of the capacitor c are determined by the desired resonant frequency of the resonant circuit in the presently preferred embodiment the tag 20 preferably resonates at or near 8 2 mhz which is one commonly employed frequency used by electronic security systems from a number of manufacturers it will be apparent to those of ordinary skill in the art however that the frequency of the eas system may vary according to local conditions and regulations thus this specific frequency is not to be considered a limitation of the present invention deactivation of the tag which typically occurs at the point of sale or checkout counter prevents the resonant circuit from resonating within the detection frequency range so that the electronic security system no longer detects the article passing through the surveillance zone of the electronic security system fig3 a.