Electronic equipment theft deterrent system

• US 5,767,771 A
• Filed: 03/08/1996
• Issued: 06/16/1998
• Est. Priority Date: 03/08/1996
• Status: Expired due to Fees

• Current Assignee: Independent Security Appraisers of Canada
• Original Assignee: Independent Security Appraisers of Canada
• Inventors: Lamont, Leonard A.
• Primary Examiner(s): SWANN III, GLEN R
• Application Number:
  US08/613,155
• Time in Patent Office: 830 Days
• Field of Search: 340/571, 340/568, 340/522
• US Class Current: 340/571
• CPC Class Codes: G08B 13/1409 for removal detection of electrical appliances by detecting their physical disconnection from an electrical system, e.g. using a switch incorporated in the plug connector

Abstract

A theft deterrent system disables one or more components of electronic equipment in response to the unauthorized removal of the electronic equipment. An AC control module is disposed between an AC source and a theft deterrent circuit. The theft deterrent circuit has a first sensor to detect the presence of AC power at the theft deterrent circuit, an alarm circuit having a second sensor to detect unauthorized removal of the electronic equipment, a DC source for supplying power to the alarm circuit and for arming the alarm circuit once the first sensor has detected the absence of AC power to the theft deterrent circuit and a disabling circuit having a high voltage output connected to one or more of the components of the electronic equipment, in order to permanently disable the components when the second sensor detects unauthorized removal of the electronic equipment. A master control unit connected via AC power lines to the AC control module is used for activating and deactivating the AC control module, such that the theft deterrent circuit can be armed remotely from the master control unit when AC power to the theft deterrent circuit is removed.

Claims

1. A theft deterrent system for disabling one or more components of electronic equipment in response to the unauthorized removal of the electronic equipment, the theft deterrent circuit comprising, in combination:

(a) an AC control module having an input connected to an AC source and an output connected to said electronic equipment;

(b) a theft deterrent circuit comprised of;

(i) an AC power relay to detect the presence or absence of AC power to said electronic equipment;

(ii) an alarm circuit having a sensor to detect unauthorized removal of the electronic equipment;

(iii) a DC source for supplying power to said alarm circuit, said DC source being enabled to supply power to said alarm circuit and place said alarm circuit in a stand-by mode once said AC power relay has detected the absence of AC power to said electronic equipment; and

(iv) a disabling circuit having a high voltage output connected to one or more of said components in order to permanently disable the said components, when said sensor detects unauthorized removal of the electronic equipment;

(c) a master control unit connected via AC power lines to said AC control module for activating and deactivating said AC control module and thereby activating and deactivating AC power to said electronic equipment.

2. A theft deterrent system as defined in claim 1, wherein said AC power relay is connected at the output of said AC control module such that said alarm circuit is placed on a stand-by mode once absence of AC power is detected at the output of said AC control module.

3. A theft deterrent system as defined in claim 2, wherein said alarm circuit comprises a motion detector and an audible alarm generator, said audible alarm generator being triggered when said motion detector detects movement of the electronic equipment.

4. A theft deterrent system as defined in claim 3, further comprising a timing circuit connected between said alarm circuit and disabling circuit, such that when said motion detector is triggered, a timing cycle in said timing circuit is started and said disabling circuit is not activated until a predetermined time measured by the timing circuit has elapsed.

5. A theft deterrent system as defined in claim 4, wherein said disabling circuit comprises an oscillator circuit connected to a multiplier circuit via a transformer, such that a low voltage at the input of the oscillator circuit can be amplified to a high voltage at the output of the multiplier circuit.

6. A theft deterrent system as defined in claim 5, wherein said master control unit communicates with said AC control module over said AC power lines, using an FM signal superimposed over AC.

7. A theft deterrent system as defined in claim 6, wherein said electronic equipment comprises a desktop computer.

8. A theft deterrent system as defined in claim 1, wherein said AC power relay is connected at the input of said AC control module such that said alarm circuit is placed on a stand-by mode once absence of AC power is detected at the input of said AC control module.

9. A theft deterrent system as defined in claim 8, wherein said alarm circuit comprises a motion detector and an audible alarm generator, said audible alarm generator being triggered when said motion detector detects movement of the electronic equipment.

10. A theft deterrent system as defined in claim 9, further comprising a timing circuit connected between said alarm circuit and disabling circuit, such that when said motion detector is triggered, a timing cycle in said timing circuit is started and said disabling circuit is not activated until a predetermined time measured by the timing circuit has elapsed.

11. A theft deterrent system as defined in claim 10, wherein said disabling circuit comprises an oscillator circuit connected to a multiplier circuit via a transformer, such that a low voltage at the input of the oscillator circuit can be amplified to a high voltage at the output of the multiplier circuit.

12. A theft deterrent system as defined in claim 11, wherein said master control unit communicates with said AC control module over said AC power lines, using an FM signal superimposed over AC.

13. A theft deterrent system as defined in claim 12, wherein said electronic equipment comprises a desktop computer.