Abstract: The present invention provides a burglar alarm system capable of accurately discriminating an alarm from a disturbance noise approximate to the alarm such as background music, ambient noises, etc. In a burglar alarm system comprising an alarm unit attached to an object to be protected from theft to emit an alarm of a particular frequency and an alarm sensor device for issuing an alarm signal upon sensing an alarm from the alarm unit, the alarm sensor device counts a predetermined number of waveform pulses of a received sound (S2, S5) more than once (S1˜S3, S4˜S6), determines, if it transpires that a differential between counted values falls within a predetermined time range, that the received sound is an alarm and issues an alarm signal (S7).

Abstract: The present invention provides a burglar alarm system capable of accurately discriminating an alarm from a disturbance noise approximate to the alarm such as background music, ambient noises, etc. In a burglar alarm system comprising an alarm unit attached to an object to be protected from theft to emit an alarm of a particular frequency and an alarm sensor device for issuing an alarm signal upon sensing an alarm from the alarm unit, the alarm sensor device counts a predetermined number of waveform pulses of a received sound (S2, S5) more than once (S1˜S3, S4˜S6), determines, if it transpires that a differential between counted values falls within a predetermined time range, that the received sound is an alarm and issues an alarm signal (S7).

Abstract: The invention provides an antitheft system comprising an alarm unit 1 attachable to a commodity, and an antitheft gate 2 installed in the vicinity of an exit of a store and having incorporated therein a transmitting circuit for producing an alarm activating signal for the alarm unit 1. The alarm unit 1 comprising a buzzer 1, receiving antenna 15 and control circuit 18. The control circuit 18 comprises an interrupt detecting circuit 18b alternatively settable in an interrupt permitting mode wherein the signal received by the antenna 15 is permitted to pass through the circuit 18b or an interrupt prohibiting mode wherein the received signal is prevented from passing therethrough, and a CPU 18a for judging whether the received signal input from the interrupt detecting circuit 18b is the alarm activating signal.

Abstract: The invention provides an antitheft system comprising an alarm unit 1 attachable to a commodity, and an antitheft gate 2 installed in the vicinity of an exit of a store and having incorporated therein a transmitting circuit for producing an alarm activating signal for the alarm unit 1. The alarm unit 1 comprising a buzzer 1, receiving antenna 15 and control circuit 18. The control circuit 18 comprises an interrupt detecting circuit 18b alternatively settable in an interrupt permitting mode wherein the signal received by the antenna 15 is permitted to pass through the circuit 18b or an interrupt prohibiting mode wherein the received signal is prevented from passing therethrough, and a CPU 18a for judging whether the received signal input from the interrupt detecting circuit 18b is the alarm activating signal.

Abstract: This invention provides an antitheft system comprising an antitheft gate 2 installed in the vicinity of an exit of a store, and an alarm unit 1 attached to a commodity. The gate 2 has incorporated therein a signal generator 21 for producing a notifying signal, and an alarm device 22 capable of producing an alarm. The alarm unit 1 comprises an electronic buzzer 11, a receiving antenna 15 for receiving the notifying signal from the signal generator 21 of the gate 2, and a control circuit 17 for operating the buzzer 11 upon the antenna 15 receiving the notifying signal. The alarm device 22 of the gate 2 comprises an alarm producing circuit 225 capable of producing an alarm, a receiving antenna 221 for receiving electromagnetic waves generated by the buzzer 11 by operating the buzzer 11, and a control circuit 224 for operating the alarm producing circuit 225 upon the antenna 221 receiving the electromagnetic waves. The construction described renders the alarm unit 1 compact.

Abstract: An antitheft system embodying the invention comprises an alarm unit 2 attached to a commodity for producing an alarm on receiving a detection signal or an alarm activating signal while stopping the alarm on receiving an alarm stopping signal, and a signal generator provided on a cashier's counter for producing alarm activating signals and alarm stopping signals alternately. When the commodity is handed by the customer to the clerk at the cashier's counter, with the alarm unit 2 attached to the commodity, the alarm unit 2 intermittently produces an alarm on receiving alarm activating signals and alarm stopping signals alternately, thereby enabling the clerk to reliably recognize that the alarm unit 2 is attached to the commodity. When the clerk thereafter removes the alarm unit 2 from the commodity, the production of alarm is forcibly ceased.

Abstract: A nullification device of the invention comprises a nullifying signal generator 15 for producing a nullifying signal, and a controller 14 for measuring a predetermined period of time and on/off-controlling a mode change switch 16 provided between the signal generator 15 and a transmitting antenna 18. On the other hand, an activation device comprises a generator 23 for producing an activating signal for the nullification device. The activation device and the nullification device have connection terminals a, b and a', b', respectively, where the devices are in contact with each other, with the nullification device placed in a accommodating recess in the activation device.