Abstract: An EAS presence detection system includes a transmitter for transmitting an electromagnetic radiation signal of a first predetermined frequency into a surveillance zone; a tag for attachment to an article to be detected within the surveillance zone, the tag containing a transponder including a material that, when in the presence of a magnetic bias field within a predetermined magnetic field intensity range, responds to detection of electromagnetic radiation of the said first predetermined frequency by transmitting electromagnetic radiation of a second predetermined frequency that is either a multiple harmonic or a frequency-divided quotient of the first predetermined frequency or at the first frequency; a detection system disposed for detecting radiation of the second predetermined frequency within the surveillance zone; and a magnetic field source for providing a magnetic bias field within the predetermined magnetic field intensity range within the surveillance zone.

Abstract: A pin-and-clutch theft-deterrent device that enables instantaneous detection of separation-force tampering with the theft-deterrent device. The device includes a pin in one component and a clutch assembly in a second component for attaching the device to an article to be protected by grasping the pin with the clutch to provide a predetermined retaining force for resisting separation of the components by prying or pulling the components apart; a force-sensitive switch assembly for detecting application to the two components of at least a predetermined threshold separation force applied in opposition to the predetermined retaining force; and a transponder coupled to the switch assembly for responding to an irradiated interrogation signal by radiating an alarm signal when the switch assembly detects application to the two components of at least the predetermined threshold separation force.

Abstract: A batteryless, portable, frequency divider includes a first resonant circuit that is resonant at a first frequency for receiving electromagnetic radiation at the first frequency; and a second resonant circuit that is resonant at a second frequency that is one-half the first frequency for transmitting electromagnetic radiation at the second frequency; and a circuit element electrically connecting the first resonant circuit to the second resonant circuit.

Abstract: A batteryless, portable, frequency divider according to the present invention includes a first resonant LC circuit that is resonant at a first frequency for receiving electromagnetic radiation at the first frequency; and a second resonant LC circuit that is resonant at a second frequency that is one-half the first frequency for transmitting electromagnetic radiation at the second frequency. The first circuit is coupled only magnetically to the second circuit to transfer energy to the second circuit in response to receipt by the first circuit of electromagnetic radiation at the first frequency. Each circuit includes a variable reactance element, such as a variable capacitance diode or varactor.

Abstract: A batteryless, portable, frequency divider according to the present invention includes a first resonant LC circuit that is resonant at a first frequency for receiving electromagnetic radiation at the first frequency; and a second resonant LC circuit that is resonant at a second frequency that is one-half the first frequency for transmitting electromagnetic radiation at the second frequency. The first circuit is coupled only magnetically to the second circuit to transfer energy to the second circuit at the first frequency in response to receipt by the first circuit of electromagnetic radiation at the first frequency. The second circuit includes a variable reactance element, such as a variable capacitance diode or varactor, in which the reactance varies with variations in energy transferred from the first circuit for causing the second circuit to transmit electromagnetic radiation at the second frequency in response to the energy transferred from the first circuit at the first frequency.

Abstract: A recording-tape-reel assembly, such as used with a computer, has an electronic tag to enable the presence of the assembly to be detected in a presence detection system in order to inhibit the unauthorized removal of the assembly from premises equipped with such a system. The assembly includes a reel for holding a recording tape, an electronic tag for enabling detection of the presence of the assembly in a presence detection system, and a housing that isolates the electronic tag from the recording tape and makes the tag inaccessible to users of the assembly. Electronic tags are housed in both reels and cassettes that contain reels.

Abstract: A batteryless, portable, frequency divider consists of a single resonant circuit consisting of an inductor and a diode. The resonant circuit detects electromagnetic radiation at a first predetermined frequency and responds to said detection by transmitting electromagnetic radiation at a second frequency that is one-half of the first frequency. The circuit is resonant at the second frequency when the voltage across the diode is zero. The frequency divider is utilized in a presence detection system that uses a tag containing the frequency divider. The system transmits electromagnetic radiation at the first frequency into a surveillance zone, and detects the second frequency to detect the presence of the tag in the surveillance zone.