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CROSS REFERENCES TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to electronic article surveillance (EAS) tags, and more particularly, to an EAS tag with improved anti-defeat mechanisms. 
     2. Description of the Related Art 
     Electronic article surveillance systems are well known in the art and are used for inventory control and to prevent theft and similar unauthorized removal of articles from a controlled area. Typically, in such systems a system transmitter and a system receiver are used to establish a surveillance zone, which must be traversed by any articles being removed from the controlled area. An EAS tag is affixed to each article and includes a marker or sensor adapted to interact with a signal being transmitted by the system transmitter into the surveillance zone. This interaction causes a further signal to be established in the surveillance zone which further signal is received by the system receiver. Accordingly, upon movement of a tagged article through the surveillance zone, a signal will be received by the system receiver, identifying the unauthorized presence of the tagged article in the zone. 
     Certain types of EAS tags are deactivatable, are disposable, and may be permanently affixed to articles. Other types of EAS tags have been designed to be reusable and, thus, include releasable attachment devices for affixing the tags to the articles. Such attachment devices are further designed to be releasable by authorized personnel only so that unauthorized removal of a tag from its article is avoided. To this end, many attachment devices are made releasable only through the use of an associated special tool or detaching mechanism. 
     U.S. Pat. No. 5,426,419, entitled Security Tag Having Arcuate Channel and Detacher Apparatus for Same, (the &#39;419 patent) the disclosure of which is incorporated herein by reference, discloses an EAS tag that has a relatively hard tag body, which is adapted to be releasable from an article in an easy and simple manner by insertion of the arcuate probe of an associated detacher device into an arcuate channel of the tag to release a spring clamp mechanism. The spring clamp mechanism is a releasable locking mechanism that prevents removal of a tack assembly that is adapted for insertion through an article, which is captured when inserted into an opening in a portion of the tag body. 
     FIGS. 1-7 show various views of an EAS tag  1  in accordance with the principles of the invention disclosed in the &#39;419 patent, a portion of the description of which follows herein. As shown in FIG. 1, the tag  1  includes an upper housing  2  having side walls  2 A,  2 B,  2 C and  2 D which are joined by a top wall  2 E. The tag  1  also includes a lower housing  3  having side walls  3 A,  3 B,  3 C and  3 D which are joined by a bottom wall  3 E. The upper and lower housings  2  and  3  are joined or mated along corresponding or associated side wall pairs ( 2 A,  3 A), ( 2 B,  3 B), ( 2 C,  3 C) and ( 2 D,  3 D) to form a closed tag body  1 A. 
     The housings  2  and  3  are preferably made of a hard or rigid material. A usable rigid or hard material might be a hard plastic such as, for example, an injection molded ABS plastic. If a plastic is used, the mating side walls of the housings can be joined by an ultrasonic weld  1 B or like joining mechanism. 
     The tag  1  further includes a tack assembly  4  shown as having an enlarged tack head  4 A and an elongated tack body  4 B provided with slots or grooves  4 C and a pointed forward end  4 D (see, FIGS. 1,  2  and  6 A). The tack assembly  4  is used to attach the tag body  1 A to an article  51 , which is to be protected by the EAS tag  1 . 
     In order to sense the tag  1  and, therefore, detect the presence of the tag and the attached article  51 , the inner surfaces  2 F and  3 F of the walls  2 E and  3 E of the housings  2  and  3  are provided with frame members  2 G and  3 G which together define an interior cavity  1 C for receiving an EAS sensor  5  (see, FIGS. 2,  3  and  4 A). The EAS sensor  5  can be any sensor that generates detectable EAS signals, and may be an acoustically or mechanically resonant magnetic sensor such as, but not limited to, that disclosed in U.S. Pat. Nos. 4,510,489 and 4,510,490. Possible other magnetic EAS sensors usable for the sensor  5  might be, but not limited to, those disclosed in U.S. Pat. Nos. 4,686,516 and 4,797,658 and possible RF EAS sensors might be, but not limited to, those disclosed in U.S. Pat. Nos. 4,429,302 and 4,356,477. 
     As above-noted, the article  51  is joined to the tag body  1 A by the tack assembly  4 . This is accomplished by inserting the tack body  4 B into an opening  2 H in the wall  2 E of the upper housing  2 . When the tack body  4 B is fully inserted, the pointed end  4 D of the tack is received in an upstanding cavity or collar  3 H extending from the inner surface  3 F of the lower housing wall  3 E. The tack head  4 A, in turn, seats in a recessed area  21  in the upper surface  2 J of the wall  2 E. The article  51  is thus held between the tack head  4 A and the latter wall. 
     Member  6  to be discussed in greater detail below is provided within the tag body  1 A for releasably preventing the tack body from being withdrawn from the tag body. The tack assembly  4 B and the article  51  thus become releasably locked to the EAS tag by the member  6 . 
     The EAS tag  1  is further adapted so that access to the member  6  for releasing same is made difficult for other than authorized personnel. To this end, the tag body  1 A is configured so that access to the member  6  is through an arcuate channel  7  (see FIGS. 1,  3 ,  4 A,  4 B,  6 A and  6 B) defined by one or more inner walls and by parts of the side walls and upper and lower walls of the tag body  1 A. With this configuration, a special arcuate probe  8  is needed to reach and release the member  6  and, thus, detach the tack assembly  4  and the article from the tag body  1 A. 
     As shown, the arcuate channel  7  is defined by a curved inner wall  7 A. This wall extends upward from the inner surface  3 F of the bottom housing  3  to abut the inner surface  2 F of the upper housing  2 . The wall  7 A is further spaced from the side wall  3 D of the bottom housing  3  and its outward end  7 A′ terminates at an inward curved part  3 A′ of the side wall  3 A. The inward curved part  3 A′ of the wall  3 A results in a space or slot  9 A between the side walls  3 A and  3 D of the lower housing  3 . 
     The slot  9 A cooperates with a similar slot  9 B between the sides wall  2 A and  2 D of the upper housing  2  to define a second opening  9  for providing entry or access into the outward end  7 ′ of the channel  7 . At this entry point, the side wall  2 A also curves inwardly at a part  2 A′, the latter part  2 A′ mating with the curved side wall part  3 A′ of the side wall  3  of the lower housing  3 . 
     The channel  7  is further defined by a second curved wall  7 B (see, FIGS. 4A and 7) extending downwardly from the inner surface  2 F of the upper housing  2 . The wall  7 B is situated outward of the inner end  7 A″ of the curved wall  7 A and extends beyond this end to the frame member  2 G. 
     The presence of the wall  7 B changes or alters the configuration of the channel  7  at its inner end  7 ″ which end lies adjacent the member  6  (see, FIG.  6 B). This change or alteration in configuration defines a keyway for the channel  7  which must be accommodated by the probe  8  to pass through the channel and gain access to the member  6 . 
     The wall  7 B changes the channel cross section from substantially rectangular to substantially L-shaped. This is illustrated in the cross section of FIG. 7 which has been taken along the line B—B in FIG. 1 so that the cross section of the channel end  7 ″ is made visible. 
     FIGS. 6A and 6B are enlarged views of the section of the lower housing  3  containing the member  6  and the arcuate channel  7 . In FIG. 6A, the arcuate probe  8  is shown as received in and guided by the channel  7  to the member  6  for the purpose of releasing same. As can be seen, the forward end  8 A of probe  8  is L-shaped and, thus, fit within the L-shaped keyway defined by inner end  7 ″ of the channel. In FIG. 6B, the probe  8  is shown as withdrawn from the channel. 
     Adjacent the inner end  7 ″ of the channel  7 , the lower and upper housings  2  and  3  are provided with further curved walls  9  and  11  which terminate in wall sections  9 A and  11 A abutting the end walls  2 D and  3 D. The walls  9  and  11  are outward of the channel  7  and, with the end walls  2 D and  3 D, define a trap area  13 , which prevents access to the member  6 . This area provides a safety measure for blocking unauthorized objects introduced into the channel  7  of the tag body  1 A in an attempt reach the member  6 . 
     As above-noted, the member  6  is adapted to releasably prevent the tack body  4 B from being withdrawn from the tag body  1 A. More particularly, the member  6  is specifically adapted to accommodate release of the tack body  4 B via the arcuate probe  8  moving in the arcuate channel  7 . The member  6  is shown in detail in FIGS. 6A and 6B and in an exploded view in FIG.  5 . 
     As shown, the member  6  is in the form of a spring clamp having a clamp body  14  and jaws  15  and  16 . The clamp body includes a mounting part  1   4 A extending laterally of the jaw  15  and a release part  144 B extending laterally of the jaw  16 . The mounting part  14 A includes a mounting aperture  14 A′. 
     Each of the jaws  15 ,  16  extends outwardly of the plane of the clamp body  14  and then inwardly toward the other jaw. The jaws  15 ,  16 , furthermore, terminate in facing edges  15 A and  16 A. These edges extend from a common edge  14 C of the clamp body  14  inwardly toward each other, then curve outwardly away from each other to define an aperture  14 C′ (typically, circular or elliptical) for receiving the tack body  4 B. The edges  15 A and  16 A then continue in aligned fashion and end in an elongated, lateral slot  14 D in the clamp body  14 . The latter slot lies inward of a further clamp body edge  14 E, which opposes the clamp body edge  14 C. 
     A further laterally extending elongated spring sleeve or arm  17  is attached by a joint area  18  to the side  14 E′ of the edge  14 E bordering the mounting part  14 A. The sleeve  17  extends along the length of the edge  14 E and is also out of the plane of the clamp body. 
     For mounting and supporting the spring clamp  14 , the lower housing  3  of the tag body  1 A includes a hollow circular mount  21  with a lip  21 A and support walls  22 ,  23  and  24  (see, FIGS. 2,  3 ,  6 A and  6 B). The clamp is mounted, via the aperture  14 A′ of the mounting part  14 , on the mount  21  with the area of mounting part adjoining the aperture  14 A′ supported on the lip  21 A. A circular wall  25  of the upper housing  3  and a central cylindrical stud  26  of this housing (see, FIGS. 2 and 4A) maintain the mounting part  14 A in its mounted position, while allowing the mounting part to be rotated. The spring clamp  14  is thus able to pivot about the mounting part as will be described more fully below. 
     The back end  14 A″ of the mounting part  14 A and the lateral part of the clamp connecting the mounting part  14 A and the release part  14 B are supported on the support walls  22  and  24 , while the release part is carried by the wall  23 . The spring sleeve  17  rests with one end  17 A in a slot  24 A in the support wall  24 . 
     When the pointed end  4 D of the tack body  4 B is introduced in the downward direction through the opening  2 H in the upper housing  2 , the part  2 K of the upper housing, which part is shaped to fit within the hollow of the spring clamp body  14  above the jaws  15 ,  16  and carries the opening  2 H, directs the tack body to the aperture  14 C′ defined by the facing edges  15 A,  16 A of the jaws. This causes the jaws to spread or open and allow the tack body  4 B to pass through the jaws. 
     When the downward tack travel is stopped at a desired slot  4 C, i.e., a slot which provides a tight fit of the tack head  4 A and article  51  to the wall  2 E of upper housing  2 , the jaws  15 ,  16  retract and clutch the tack body  4 B. In this position, the jaws  15 ,  16  prevent upward movement of the tack  4 . The tack  4  and article  51  thus become locked to the tag body  1 A. 
     In order to release the tack  4  from the tag body  1 A, the arcuate probe  8  is now introduced into the opening of the tag body  1 A via rotation of the probe about its rearward end  8 B. This causes the probe to be moved in and guided by the channel  7  until the L-shaped forward end  8 A of the probe reaches and passes into the L-shaped inner end  7 ″ of the channel  7 . This brings the probe end  8 A to the part of the common edge  14 C bordering the release part  14 B of the clamp body  14 . 
     Continued rotational movement of the probe  8  then causes a force on the release part  14 B. This force, in turn, causes the clamp body  14  to rotate about the support area  14 A on the mount  21 . The jaws  15 ,  16  are thus enabled to spread apart or open due to the force of the tack body  4 B, which is held stationary by the collar  3 H, acting on the walls of the aperture  14 C′. The aperture  14 C′ thus expands, releasing the tack body  4 B from the grip or clutch of the jaws. The tack  4  can now be moved in the upward direction past the jaws, via an upward force on the tack head  4 A, thereby withdrawing and separating the tack body  4 B from the tag body  1 A and the article  51  from the tag  1 . 
     During rotation of the spring clamp body  14  as a result of the in-plane force exerted by the probe  8 , the spring arm  17  at the joint  18  is compressed. After the tack  4  is separated from the tag body  1 A, the probe  8  is rotated in the reverse direction. This reverse rotation disengages the probe from the release part  14 A of the spring clamp  14  as the probe  8  is withdrawn from the channel  7 . The force on the spring clamp  14  is thus removed and the spring arm  17  expands. This causes the spring clamp  14  to rotate in the opposite direction about the support area  14 A. The spring clamp  14  is thereby brought back to its original position awaiting reentry of the tack body  4 B for again attaching an article to the tag  1 . 
     Detaching assemblies which incorporate the arcuate detaching probe  8 , and can be used to rotate the probe as above-described to detach the tack  4  from the tag  1  are fully illustrated in the &#39;419 patent, which has been incorporated herein by reference. It should be noted that the spring clamp  14  of the tag  1  can be constructed of spring sheet metal. The probe  8 , in turn, can be constructed of hardened tool steel. 
     The EAS tag of the &#39;419 patent is difficult to defeat, but attempts are constantly made to defeat the tags by damaging the tags or by unauthorized removal of the tags from the article to which they are attached to prevent detection of the articles as they pass through the surveillance zones. Once an EAS tag is put into service, attempts at unauthorized removal begin. After a period of time, defeating techniques may become known to persons wanting to remove articles undetected by associated EAS systems. Modifications and improvements to the EAS tag become a natural progression in an attempt to stay ahead of the known defeat techniques. U.S. patent application Ser. No. 09/634,236, filed on Aug. 8, 2000, the disclosure of which is incorporated herein by reference, illustrates certain improvements to the EAS tag disclosed in the &#39;419 patent to make defeating the tag more difficult. Further improvements to prevent unauthorized tag defeats are disclosed hereinbelow. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with a first aspect of the present invention, an electronic article surveillance tag is provided in which the tag includes a tag body and with a tack assembly for attaching the tag body to an article. The tack assembly includes a tack head and a tack body, which is receivable in the tag body and the tag body is provided with a preventing mechanism for releasably preventing withdrawal of the tack body. Channel defining structure within the tag body defines an arcuate channel. This channel leads to the preventing mechanism and permits an arcuate probe to be guided to such mechanism for releasing same. Release of the preventing mechanism permits withdrawal of tack body thereby separating the tack assembly and article from the tag body. A sensor detectable by an electronic article surveillance system is disposed in said tag body. A shield is provided in said tag body adjacent the sensor to prevent insertion of an instrument through the tag body and into the sensor to damage the sensor. 
     The preventing mechanism can include a receiving and clutching mechanism, which receives and clutches the tack body, thereby preventing withdrawal of the tack body from the tag body. A release part of the receiving and clutching mechanism when engaged causes the receiving and clutching mechanism to release, thereby allowing withdrawal of the tack body. A second opening in the tag body leads to the arcuate channel which, in turn, leads to the release part of the receiving and clutching mechanism to allow the arcuate probe to engage same to effect the release. A shield is disposed in the tag body adjacent the releasing and clutching mechanism to prevent unauthorized release of the receiving and clutching mechanism by other than the arcuate probe. 
     The above described shield in said tag body adjacent the sensor to prevent insertion of an instrument through the tag body and into the sensor to damage the sensor can be included in the tag body with the shield used to prevent unauthorized release of the tack assembly. 
     In a second aspect of the present invention, an electronic article surveillance tag is provided in which the tag includes a tag body and with a tack assembly for attaching the tag body to an article. The tack assembly includes a tack head and a tack body, which is receivable in the tag body and the tag body is provided with a preventing mechanism for releasably preventing withdrawal of the tack body. Channel defining structure within the tag body defines an arcuate channel. This channel leads to the preventing mechanism and permits an arcuate probe to be guided to such mechanism for releasing same. Release of the preventing mechanism permits withdrawal of tack body thereby separating the tack assembly and article from the tag body. A sensor detectable by an electronic article surveillance system is disposed in said tag body. An alarm is disposed within the tag body, for sounding an audible alarm if the tack assembly is withdrawn from the tag body without the arcuate probe being guided through the arcuate channel to the preventing mechanism. 
     An LED or other light-emitting device can be made visible on the exterior of the tag body to periodically flash when the alarm is armed. 
     A plurality of relatively small apertures can be disposed on the tag body to permit the audible sound from the alarm to travel from the interior of the tag body to the exterior of the tag body. The plurality of apertures covers a sufficient portion of the tag body to prevent external localization of the position within the tag body of a sound emitting mechanism for generating the sound from the alarm. 
     A magnet switch for triggering the alarm when a relatively strong magnetic field is incident on the tag body can be included. 
     The preventing mechanism can include a receiving and clutching mechanism, which receives and clutches the tack body, thereby preventing withdrawal of the tack body from the tag body. A release part of the receiving and clutching mechanism when engaged causes the receiving and clutching mechanism to release, thereby allowing withdrawal of the tack body. A second opening in the tag body leads to the arcuate channel which, in turn, leads to the release part of the receiving and clutching mechanism to allow the arcuate probe to engage same to effect the release. A first switch put into a first state by the tack body upon insertion into the tag body. A second switch put into a first state by the tack head upon insertion of the tack body into the tag body. A third switch put into a first state by the arcuate probe when the arcuate probe is introduced into the arcuate channel to engage the receiving and clutching mechanism. The alarm sounds when the first switch is put into a second state without the third switch in its first state, and the alarm also sounds when the second switch is put into a second state without the third switch in its first state. 
     A lanyard can be used to attach the tag to an article. The alarm can sound when the lanyard is cut or broken or otherwise becomes discontinuous. 
     In a third aspect of the present invention, an electronic article surveillance tag is provided in which the tag includes a tag body and with a tack assembly for attaching the tag body to an article. The tack assembly includes a tack head and a tack body, which is receivable in the tag body and the tag body is provided with a preventing mechanism for releasably preventing withdrawal of the tack body. Channel defining structure within the tag body defines an arcuate channel. This channel leads to the preventing mechanism and permits an arcuate probe to be guided to such mechanism for releasing same. Release of the preventing mechanism permits withdrawal of tack body thereby separating the tack assembly and article from the tag body. A sensor detectable by an electronic article surveillance system is disposed in said tag body. An LED or other light-emitting device can be made visible on the exterior of the tag body to periodically flash to simulate that the tag contains an armed alarm. 
     In a fourth aspect of the present invention, an electronic article surveillance tag is provided in which the tag includes a tag body and with a tack assembly for attaching the tag body to an article. The tack assembly includes a tack head and a tack body, which is receivable in the tag body and the tag body is provided with a preventing mechanism for releasably preventing withdrawal of the tack body. Channel defining structure within the tag body defines an arcuate channel. This channel leads to the preventing mechanism and permits an arcuate probe to be guided to such mechanism for releasing same. Release of the preventing mechanism permits withdrawal of tack body thereby separating the tack assembly and article from the tag body. A sensor detectable by an electronic article surveillance system is disposed in said tag body. An alarm is disposed within the tag body, for sounding an audible alarm if the tack assembly is withdrawn from the tag body without the arcuate probe being guided through the arcuate channel to the preventing means. A first switch put into a first state by the tack body upon insertion into the tag body. A second switch put into a first state by the tack head upon insertion of the tack body into the tag body. A third switch put into a first state by the arcuate probe when the arcuate probe is introduced into the arcuate channel to engage the receiving and clutching mechanism. The alarm sounds when the first switch is put into a second state without the third switch in its first state, and the alarm also sounds when the second switch is put into a second state without the third switch in its first state. An LED or other light-emitting device can be made visible on the exterior of the tag body to periodically flash when the alarm is armed. A plurality of relatively small apertures can be disposed on the tag body to permit the audible sound from the alarm to travel from the interior of the tag body to the exterior of the tag body. The plurality of apertures covers a sufficient portion of the tag body to prevent external localization of the position within the tag body of a sound emitting mechanism for generating the sound from the alarm. 
     A magnet switch for triggering the alarm when a relatively strong magnetic field is incident on the tag body can be included. 
     A lanyard can be used to attach the tag to an article. The alarm can sound when the lanyard is cut or broken or otherwise becomes discontinuous. 
     A shield can be provided in said tag body adjacent the sensor to prevent insertion of an instrument through the tag body and into the sensor to damage the sensor. 
     A shield can be disposed in the tag body adjacent the releasing and clutching mechanism to prevent unauthorized release of the receiving and clutching mechanism by other than the arcuate probe. 
     In a fifth aspect of the present invention a method for alarming an electronic article surveillance tag having a tag alarm disposed within a tag body, the tag body adapted to receive a tack assembly for releasable attachment of the tag to an article. The method includes providing an electronic article surveillance tag having an internal circuit for sounding an audible alarm in response to unauthorized detachment of the tag. Arming the tag alarm by insertion of a tack assembly into a tag body and sensing a first state of a tack switch, a first state of a plunger switch, and the first state of an on/off switch. Activating the tag alarm upon sensing a second state of the tack switch and the first state of the on/off switch. Activating the tag alarm upon sensing a second state of the plunger switch and the first state of the on/off switch. And, unarming the tag alarm upon sensing the second state of the on/off switch. 
     Sensing a relatively strong magnetic field incident on the tag body can activate the tag alarm. Sensing a discontinuity in an attached lanyard can activate the tag alarm. 
     In a sixth aspect of the present invention, an electronic article surveillance system having an electronic article surveillance tag attachable to an article, the electronic article surveillance tag includes a tag body and with a tack assembly for attaching the tag body to an article. The tack assembly includes a tack head and a tack body, which is receivable in the tag body and the tag body is provided with a preventing mechanism for releasably preventing withdrawal of the tack body. Channel defining structure within the tag body defines an arcuate channel. This channel leads to the preventing mechanism and permits an arcuate probe to be guided to such mechanism for releasing same. Release of the preventing mechanism permits withdrawal of tack body thereby separating the tack assembly and article from the tag body. A sensor detectable by an electronic article surveillance system is disposed in said tag body. An alarm, disposed within the tag body, for sounding an audible alarm if the tack assembly is withdrawn from the tag body without the arcuate probe being guided through the arcuate channel to the preventing mechanism. A transmitter for transmitting a first signal into a surveillance zone. A receiver for receiving a tag signal resulting from the interaction in the surveillance zone of the first signal with the detectable electronic article surveillance sensor in the tag body for detecting the presence of the tag in the surveillance zone. 
     In a seventh aspect of the present invention, an electronic article surveillance system having an electronic article surveillance tag attachable to an article, the electronic article surveillance tag includes a tag body and with a tack assembly for attaching the tag body to an article. The tack assembly includes a tack head and a tack body, which is receivable in the tag body and the tag body is provided with a preventing mechanism for releasably preventing withdrawal of the tack body. Channel defining structure within the tag body defines an arcuate channel. This channel leads to the preventing mechanism and permits an arcuate probe to be guided to such mechanism for releasing same. Release of the preventing mechanism permits withdrawal of tack body thereby separating the tack assembly and article from the tag body. A sensor detectable by an electronic article surveillance system is disposed in said tag body. A shield is provided in said tag body adjacent the sensor to prevent insertion of an instrument through the tag body and into the sensor to damage the sensor. A transmitter for transmitting a first signal into a surveillance zone. A receiver for receiving a tag signal resulting from the interaction in the surveillance zone of the first signal with the detectable electronic article surveillance sensor in the tag body for detecting the presence of the tag in the surveillance zone. 
     In an eighth aspect of the present invention, an electronic article surveillance system having an electronic article surveillance tag attachable to an article, the electronic article surveillance tag includes a tag body and with a tack assembly for attaching the tag body to an article. The tack assembly includes a tack head and a tack body, which is receivable in the tag body and the tag body is provided with a preventing mechanism for releasably preventing withdrawal of the tack body. Channel defining structure within the tag body defines an arcuate channel. This channel leads to the preventing mechanism and permits an arcuate probe to be guided to such mechanism for releasing same. Release of the preventing mechanism permits withdrawal of tack body thereby separating the tack assembly and article from the tag body. A sensor detectable by an electronic article surveillance system is disposed in said tag body. A shield is disposed in the tag body adjacent the releasing and clutching mechanism to prevent unauthorized release of the receiving and clutching mechanism by other than the arcuate probe. A transmitter for transmitting a first signal into a surveillance zone. A receiver for receiving a tag signal resulting from the interaction in the surveillance zone of the first signal with the detectable electronic article surveillance sensor in the tag body for detecting the presence of the tag in the surveillance zone. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other features and aspects of the present invention will become more apparent upon reading the following detailed description in conjunction with the accompanying drawings, in which: 
     FIG.  1 . shows a prior art EAS tag and associated detacher probe in accordance with the principles of the present invention; 
     FIG. 2 shows a cross-section of the EAS tag of FIG. 1 taken along the line A—A in FIG. 1; 
     FIG. 3 shows a view of the interior of the lower housing of the EAS tag of FIG. 1; 
     FIG. 4A shows a view of the interior of the upper housing of the EAS tag of FIG. 1; 
     FIG. 4B shows a view of the exterior of the upper housing of the EAS tag of FIG. 1; 
     FIG. 5 illustrates an exploded view of the spring clamp used in the EAS tag of FIG. 1; 
     FIGS. 6A and 6B show partial views of the interior of the lower housing of the EAS tag of FIG. 1 with the probe inserted in and withdrawn from the arcuate channel of the tag, respectively; 
     FIG. 7 is a cross section of the EAS tag of FIG. 1 taken along the line B—B in FIG. 1 with the probe inserted in the arcuate channel in the tag; 
     FIG. 8 is an exploded perspective view of an EAS tag incorporating multiple anti-defeat embodiments of the present invention. 
     FIG. 9 is an inverted perspective view of the upper tag housing member showing one embodiment of the sensor shield. 
     FIG. 10 is a perspective view of one embodiment of the clamp shield. 
     FIG. 11 is a perspective view of one embodiment of the tag on/off switch. 
     FIG. 12 is a perspective view of one embodiment of the tack switch. 
     FIG. 13 is a perspective view of the lower tag housing member showing one embodiment of the PC board and switch positions. 
     FIG. 14 is a block diagram of one embodiment the tag alarm of the prevent invention. 
     FIG. 15 is a top plan view of one embodiment of the EAS tag of the present invention. 
     FIG. 16 is a perspective view of another embodiment of the EAS tag of the present invention having a lanyard for attachment of the tag to an article. 
     FIG. 17 is a flow chart of the tag alarm switch logic of the present invention 
     FIG. 18 is a block diagram of an electronic article surveillance system for use in conjunction with the EAS tag of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 8, EAS tag  100  is illustrated incorporating the anti-defeat embodiments of the present invention. Reference numerals below are the same for identical items from prior art FIGS. 1-7. Upper tag housing member  102  and lower tag housing member  104  mate together to capture sensor  5  in a similar manner as EAS tag  1  shown in FIG.  1  and described hereinabove. The terms “upper” and “lower” refer only to the orientation of tag  100  as shown in FIG. 8, and are not structural limitations. Sensor  5  can be any sensor detectable in an EAS system as described herein. Sensor shield  106  is placed on one or both sides of sensor  5  to prevent one mode of defeat where a metal probe, screw driver, or the like, is forced through upper or lower tag housing members  102  or  104 , respectively, to damage or destroy sensor  5 . Once sensor  5  is destroyed, the article to which tag  100  is attached can be moved through the interrogation zone without setting off an EAS alarm. Sensor shield  106  is preferably made of a nonferrous metal such as stainless steel or other very hard material that does not effect the operation of sensor  5 , but which is capable of making the insertion of a metal probe or the like to damage sensor  5  extremely difficult. Referring to FIG. 9, upper tag housing member  102  is shown in an inverted position to illustrate one possible positioning of sensor shield  106 . 
     Returning to FIG. 8, a secondary shield, clamp shield  108 , is utilized to prevent another defeat technique. A probe can be forced through upper or lower housing  102  or  104 , respectively, to engage spring clamp  6 , illustrated in FIGS. 5 and 6A, to rotate spring clamp  6  about support area  14 A to release tack body  4 B. Thus, a probe forced through upper or lower housing  102  or  104 , respectively, can be made to release tack  4  in a similar manner to that described hereinabove in relation to using detaching probe  8 . Clamp shield  108  can be made of a metal such as stainless steel or other very hard material that is capable of making the insertion of a metal probe or the like through upper or lower tag housing members  102  or  104 , respectively, to act upon spring clamp  6  extremely difficult. FIG. 10 illustrates an embodiment of clamp shield  108  configured to be used with EAS tag  100 . The exact shape of clamp shield  108  will depend upon the EAS tag to which it is to be installed. 
     Another preventative measure to prevent tag defeat is a self-alarming tag alarm  150 . Tag alarm  150  is fully described hereinbelow and shown in FIG. 14. A self-alarming tag alarm is an alarm signal emitted by the tag itself, and is not the alarm signal emitted by the EAS system when the EAS tag is carried into an interrogation zone. Printed circuit (PC) board  110  contains the circuitry for the alarm, which goes off if the tag  100  is detached by other than detacher probe  8 , as fully described hereinbelow. Battery  112  fits into cavity  113 , and a piezo transducer  152 , shown in FIG. 14, fits into cavity  114 , which are both used in conjunction with circuitry on PC board  110  to form the alarm. The alarm can be configured so that battery  112  can be placed into cavity  113  or cavity  114 , and the piezo transducer can be placed into the unused cavity. The series of apertures  115  and  116  through the upper and lower tag housing members, respectively, cover the area adjacent both cavities  113  and  114 . Because the apertures cover the area adjacent cavities  113  and  114 , the apertures  115  and  116  cannot be used as a localized target to direct a probe to the piezo in an attempt to destroy or damage it. A probe forced directly into the piezo could damage or destroy the piezo, but a probe indiscriminately inserted into the tag  100  could set off the tag alarm. The tag alarm will sound upon unauthorized removal of tack  4  from tag  100  according to the position of plunger switch  118 , on/off switch  120 , and tack or pin switch  122 , which are used to provide alarming logic as fully described hereinbelow. On/off switch  120  and tack switch  122  are better seen in FIGS. 11 and 12, respectively. 
     Referring to FIGS. 8 and 13, when a tack assembly  4  (shown in FIGS. 1 and 2) is inserted into aperture  124 , the bottom of tack head  4 A depresses plunger switch  118 , which protrudes slightly through aperture  126  in upper tag housing member  102 , and tack body  4 B simultaneously contacts tack switch  122  moving it into a contact on PC board  110 . Both plunger switch  118  and tack switch  122  must be contacted to arm tag  100 . Once tag  100  is armed, if either switch  118  or  122  are opened, the tag alarm will sound. If only tack switch  122  was used to arm tag  100 , the tack head  4 A could be cut or pried off and the tag would not alarm. If only plunger switch  118  is used to arm tag  100 , then inadvertent pressing and releasing of plunger switch  118  during normal handling could set off the tag alarm. Once armed, to disarm or turn off the tag alarm of tag  100 , on/off switch  120  must make contact with a suitable contact area  128  on PC board  110 . On/off switch  120  is adapted to rotate in conjunction with spring clamp  6  during normal detachment of tag  100  using conventional detacher probe  8 . Upon rotation, switch contacts  121  engage contact area  128 , thus switching the alarm of tag  100  off. The tag alarm switch logic is fully described hereinbelow. 
     Referring to FIG. 14, a block diagram of one embodiment of tag alarm  150  is illustrated. Microprocessor  155  is connected to piezo  152 , tack or pin switch  122 , plunger switch  118 , on/off switch  120 , and battery  112 . Microprocessor  155  generates the signal to drive piezo  152 , based upon the switch logic, which is explained fully hereinbelow. Piezo  151  can be driven at about 3 kHz steady, or to conserve battery life, can be pulsed, for example, at 1 Hz, or can be frequency modulated with a deviation of 250 Hz and a modulation frequency of 4 Hz, or driven in a combination of modulation techniques. Piezo  152  can be any small transducer that makes an audible sound and that can be driven at relatively low power. 
     In addition to the switches described above, magnet switch  130  is connected to microprocessor  154 . One embodiment of tag  100  includes a magnetomechanical sensor  5 . Magnetomechanical sensors include a magnetostrictive resonator that resonates at a preselected frequency when biased by a magnetic field. Magnetomechanical sensors are thus effected by a magnetic field, and one defeat method involves placing a relatively strong magnet next to the tag so the resonator is no longer biased correctly and no longer resonates at the desired frequency. If the tag does not resonate at the desired frequency, it will not be detected when moved through an interrogation zone. Tag  100  can include a magnet switch  130 , which is closed upon exposure to an externally applied magnetic field, thus alarming tag  100 . The magnet switch  130  can be any suitable magnet switch such as a reed switch, or a wire segment with a free end positioned within an exposed wire loop, and which moves in an applied magnetic field touching the exposed wire loop to make contact and close the switch. 
     Referring also to FIG. 15, LED  132  is connected to microprocessor  154 . When tag  100  is armed, LED  132  flashes to indicate that tag  100  is active. LED  132  can be configured to flash at a desired repetition rate, for example at 3 seconds ‘on’ and 3 seconds ‘off’. To conserve battery life, the ‘on’ time for LED  132  can be pulsed or cycled at a frequency that is higher than that detectable to the human eye. Thus, during the time that LED  132  is ‘on’, it will appear to be constant but will actually be cycling ‘on’ and ‘off’ very rapidly. For example, the cycle frequency for the ‘on’ time should be greater than 50 Hz, such as 333 Hz. A flashing LED  132  indicates that tag  100  is armed, and will alarm if tampered with, which provides additional deterrence to defeat attempts. Upon alarming, the repetition rate of 3 seconds ‘on’ and  3  second ‘off’ will change, for example, cycling at a faster repetition rate. When the tag  100  is alarming, the response of LED  132  will thus be visually different than when tag  100  is in the armed state. This permits easy location of an alarming tag  100  in proximity to a plurality of armed tags that are not alarming. 
     Referring also to FIG. 16, lanyard  134  is connected to microprocessor  154 , and is used in an embodiment of tag  100 ′, which includes a lanyard  134  for attachment of tag  100 ′ to articles. Lanyard  134  attaches around or through a portion of an article and loop  135  is disposed under tack head  4 A, with tack body  4 B passing through loop  135  and into tag  100 ′. Lanyard  134  incorporates an electrical wire and if lanyard  134  is cut, microprocessor  154  will alarm tag  100 ′. 
     Referring to FIG. 17, the tag alarm switch logic is illustrated, which starts in the unarmed state  200 . When the tack  4  is inserted at  201 , the tack switch is closed and the plunger switch is enabled at  202 . When the plunger switch is closed at  203  the tag is armed at  204 . If tack  4  is removed, or if lanyard  134  is cut at  205 , without using a detacher probe  8 , tag alarm  150  will alarm at  206 . If detacher probe  8  was used at  205 , the tag is unarmed at  200 . If the tack  4  is not removed, or lanyard  134  is not cut, and the magnet switch is closed at  208  by an applied magnetic field, tag alarm  150  will alarm at  206 . If the magnet switch is not closed at  208 , and the plunger switch is released or opened at  210 , the tag will alarm at  206 , which indicates that the tack head  4 A was cut or pried off. The alarm and the tag is turned off by detachment of tack  4  by detacher probe  8  at  212 . 
     Tag  100  can be configured to have all of the tag defeat devices and methods described hereinabove or any combination thereof. For example, decoy tags could be used where LED  132  flashes to indicate the tag is armed, but the tag may not have an alarm, it may only have the flashing LED. A perpetrator will not know if the tag will alarm or not, as it will appear identical to the tags  100  that are equipped with alarms. Likewise, tag  100  may contain both shields  106  and  108 , or neither, or only one of the shields. Alternately, shields  106  and  108  can be incorporated into EAS tag  1  without any self-alarming features. 
     FIG. 18 illustrates an EAS system  301  used to detect or sense EAS tag  100  when passing through a surveillance zone  302 . EAS tag  100  is an EAS tag  1 , described hereinabove, modified to include the present invention. An interrogation signal is transmitted into the zone  302  via a transmitting device  303 . A signal resulting from interaction of the sensor  5  in the tag  100  with the transmitted signal is received at a receiver  304 , which communicates with a detection and alarm device  305 . The latter detects the received signal and generates an alarm indicating the presence of the tag  100  and the article  51  in the surveillance zone  302 . 
     The particular configurations used for the devices  303 ,  304  and  305  in the system  301  will depend on the particular nature of the sensor. For example, instead of a transmitter  303  and separate receiver  304 , one or more transceivers can be used. For the types of sensors disclosed in the hereinabove-mentioned patents, devices of the types also disclosed in these patents can be used. 
     It is understood that the above-described arrangements are merely illustrative of the many possible specific embodiments, which represent applications of the present invention. Numerous and varied other arrangements can be readily devised in accordance with the principles, of the present invention without departing from the spirit and scope of the invention.

Summary:
An EAS tag in which the tag is held to an article by an attaching assembly a part of which is releasably prevented from being withdrawn from the body of the tag. The tag body is provided with an arcuate channel through which an arcuate detacher probe can be guided for releasing the attaching assembly part. A spring clamp provides the releasable preventing function and includes jaws specifically adapted to respond to in-plane torsional forces provided by the arcuate probe which is moved through the arcuate channel by rotation to reach the spring clamp. The tag has improved anti-defeat devices and methods including one or more of the following; a shield to protect the EAS sensor, a shield to protect the releasable spring clamp, a tag self-alarm that alarms upon various unauthorized defeat attempts, an LED to signal an armed condition of the tag alarm, a magnet switch to alarm the tag upon exposure to a relatively strong magnetic field, and a plurality of apertures to decoy the position of the alarm piezo.