Apparatus for deactivating a surveillance tag

• US 4,318,090 A
• Filed: 10/27/1980
• Issued: 03/02/1982
• Est. Priority Date: 10/27/1980
• Status: Expired due to Term

• Current Assignee: Sensormatic Electronics Corporation (Johnson Controls International plc)
• Original Assignee: Sensormatic Electronics Corporation (Johnson Controls International plc)
• Inventors: Narlow, Douglas A., Stevens, Eugene
• Primary Examiner(s): Swann, III, Glen R.
• Application Number:
  US06/201,050
• Time in Patent Office: 491 Days
• Field of Search: 340/572, 343/6.5 SS, 343/6.8 R
• US Class Current: 340/572.3
• CPC Class Codes: G08B 13/2425 Tag deactivation

Abstract

A pulse source powers a wand-like probe with spaced contacts that is arranged to be applied to and drawn along the surface of a surveillance tag that contains a diode semiconductor with exposed terminals. When the probe contacts engage the diode terminals, current is passed through the diode sufficient to destroy its unidirectional conducting characteristics and thereby deactivate the tag. A cut-out circuit is included to prevent the passage of excessive current through the diode or damaging short-circuiting of the power amplifier output.

Claims

1. Apparatus for deactivating a surveillance tag, the detection of which by an interrogation station is dependent upon the condition of a semiconductor diode contained in said tag which diode is connected conductively to a first pair of contacts exposed adjacent at least one surface of said tag, said apparatus comprising a probe constructed to be brought into engagement with said one surface and moved relative thereto, said probe including a second pair of contacts that ride along said one surface during said movement of said probe so as to engage conductively said first pair of contacts, and means coupled to said second pair of contacts for furnishing thereto alternating current sufficient to deteriorate said diode during the interval of said conductive engagement such that said tag is no longer detectable by said interrogation station.

2. Apparatus according to claim 1, wherein said means comprises means responsive to a given change in potential drop across said second pair of contacts resulting from said engagement with said first pair of contacts for interrupting the flow of current through said second pair of contacts.

3. Apparatus according to claim 2, wherein said means responsive to a given change in potential drop across said second pair of contacts is also constructed and arranged upon such change in potential drop to provide a signal to an operator that a tag has been deactivated.

4. Apparatus according to claim 1, wherein said means comprises means responsive to a given change in potential drop across said second pair of contacts resulting from said engagement with said first pair of contacts for furnishing a signal to an operator that a tag has been deactivated.

5. Apparatus according to claim 1, wherein said means comprises an oscillatory source operating at an audio frequency having an output coupled to said second pair of contacts for feeding a train of pulses thereto.

6. Apparatus according to claim 5, wherein said audio frequency is about 3 KHz.

7. Apparatus according to claim 5, wherein said source output is coupled to an electro-acoustic transducer for producing an audible signal responsive to a given decrease in potential drop across said second pair of contacts resulting from engagement with said first pair of contacts to provide a signal to an operator that a tag has been deactivated.

8. Apparatus according to claim 5, wherein said source output is coupled through a given impedance to both said second pair of contacts and to a voltage comparator, and said voltage comparator includes an output coupled to a circuit interrupter that is coupled to said second pair of contacts for interrupting the flow of current through the latter whenever said voltage comparator senses a predetermined drop in the voltage applied to said second set of contacts.

9. Apparatus according to claim 8, further comprising means coupled to said circuit interrupter for resetting the latter a predetermined interval after said second pair of contacts has been disengaged from said first pair of contacts to prepare said apparatus for another deactivating sequence.

10. Apparatus according to claim 1, wherein said second pair of contacts are mounted at the end of a wand-like structure, projecting from an end face of the latter, and spaced apart a predetermined distance from each other, said second pair of contacts being configured to be drawn with a gliding contact across the surface of said tag when said wand-like structure is held at an angle to said tag surface and moved relatively thereto, and said probe includes means for guiding the positioning of said probe relative to said tag as the former is drawn across the latter.

11. Apparatus according to claim 10, wherein said tag is narrow, thin and elongated with parallel sides, said first pair of contacts are disposed at a given distance from said sides, and said means for guiding the probe comprises a pair of parallel spaced apart planar members for engaging, respectively, opposite sides of said tag when said second pair of contacts engage a surface of said tag that extends between said sides.

12. Apparatus according to claim 11, wherein said second pair of contacts comprise two U-shaped wire elements with the legs of the "U" mounted in said wand-like structure and the base of the "U" projecting to be engaged with the surface of said tag.