Abstract: The secure release apparatus is used with an anti-theft device having a member which is movable in response to an applied magnetic field. The secure release apparatus comprises a cover plate with an access opening and a permanent magnet structure which produces a concentrated magnetic field sufficiently strong to move the member. A tamper prevention structure is movable into a first position for preventing the member from moving into the concentrated field.

Abstract: The system includes a transmitter producing an electromagnetic field at a frequency repetitively swept through a predetermined range at a predetermined sweep frequency. A receiver senses a resonant frequency produced by a resonant tag circuit when the tag circuit is within the electromagnetic field and produces an output signal in response to the resonant frequency. A first noise rejection circuit is provided which accepts the output of the receiver and produces a pulse in response to selected output signals from the receiver. The selected output signals include an initial output signal and successive output signals which occur at an interval from the previous selected output signal which is at least as great as the period of the sweep frequency. The circuit then compares the frequency of the pulses produced with the sweep frequency and produces an alarm signal when the pulse frequency and sweep frequency are substantially equal.

Abstract: Disclosed is a loop antenna for the propagation of electromagnetic radiation with minimal electrostatic radiation for use in security systems. At least a single loop of conductor forms the radiating surface of the antenna. However, the loop is disposed in a tubular electrostatic shield which serves to minimize electrostatic radiation while not significantly interfering with the desired electromagnetic radiation. In preferred embodiments the electrostatic shield may be electrically grounded or a resistor may be placed in the conduction loop of the antenna to broaden the frequency response thereof. Additional preferred embodiments include twisting the single loop antenna one or more times such that two or more lobes are provided forming a twisted loop antenna. Far-field cancellation of transmitted signals is achieved and there is self cancellation in this antenna of received common mode signals.

Abstract: A locking device which includes a housing, a spring biased insert, arcuately spaced retaining balls, and cup means which is securely mounted in the housing and retains the balls and the lower end of the insert. The tapered side walls of the cup means provide a cam surface upwardly along which the balls can move when a pin is inserted in the lock. When the pin is released the balls tightly frictionally engage the pin under the bias of the spring, thereby preventing unauthorized removal of the pin.

Abstract: A fastening device for securing articles together, the device including releasably connected male and female components. The male component comprises a pin and the female component comprises a retaining insert positioned in a housing for releasably clamping the pin. When joined, the pin can not be separated from the retainer except by a special tool. The insert is of magnetic material, and an actuating tool including an electromagnet is employed to actuate the insert to permit removal of the pin. The housed insert is attached to a tag, with the tag being attached to the article which is to be sold. The tag houses an electrical circuit which activates an alarm if the tag is not properly removed at the checkout point by means of the special tool.

Abstract: A fastening device for securing articles together, the device including releasably connected male and female components. The male component comprises a pin and the female component comprises a retaining insert positioned in a housing for releasably clamping the pin. When joined, the pin can not be separated from the retainer except by a special tool. The insert is of magnetic material, and an actuating tool including an electromagnet is employed to actuate the insert to permit removal of the pin. The housed insert is attached to a tag, with the tag being attached to the article which is to be sold. The tag houses an electrical circuit which activates an alarm if the tag is not properly removed at the checkout point by means of the special tool.

Abstract: A fastening clip for securing articles together, the clip including releasably connected male and female components. The male component comprises a pin and the female component comprises a retainer for releasably clamping the pin. When joined, the pin cannot be separated from the retainer except by a specially formed tool which is insertable in the retainer. Manipulation of the tool serves to condition the retainer for removal of the pin. In a modified form of the invention, the retainer is of magnetic material, and an actuating tool including an electromagnet is employed to actuate the retainer and permit removal of the pin.

Abstract: A fastening device for securing articles together, the device including releasably connected male and female components. The male component comprises a pin and the female component comprises a retaining insert positioned in a housing for releasably clamping the pin. When joined, the pin can not be separated from the retainer except by a special tool. The insert is of magnetic material, and an actuating tool including an electromagnet is employed to actuate the insert to permit removal of the pin. The housed insert is attached to a tag, with the tag being attached to the article which is to be sold. The tag houses an electrical circuit which activates an alarm if the tag is not properly removed at the checkout point by means of the special tool.