Abstract:
A tamper switch mechanism utilized in security interface devices such as keypad installations to render them tamper-resistant, wherein the devices are generally connected to burglar alarm and fire alarm systems. More particularly, provided is a conductive tamper switch which is installed in a security interface device, such as a keypad, which upon an unauthorized attempt to dislodge the device or keypad from a wall or surface on which it is mounted, will trigger an alarm or generate a warning signal at a monitoring site indicative that an effort at tampering with the device has been effected. Also disclosed is a method of providing the tamper switch mechanism in a security interface device, such as a keypad installation.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a switch mechanism utilized in security interface devices such as keypad installations to render them tamper-resistant, wherein the devices are generally connected to burglar alarm and fire alarm systems. 
   More particularly, the present invention pertains to the provision of a conductive tamper switch which is installed in a security interface device, such as a keypad, which upon an unauthorized attempt to dislodge the device or keypad from a wall or surface on which it is mounted, will trigger an alarm or generate a warning signal at a monitoring site indicative that an effort at tampering with the device has been effected. 
   Currently, security interface devices, such as those which consist of keypad units, are normally mounted on the walls or other upright surfaces of the most diverse locations, such as in homes, apartments, offices and manufacturing sites and plants. The security interface devices are frequently equipped with tamper-indicating structures. For instance, such structures may comprises tamper switches installed in the keypads, and among other locales, which may contact electronic operative components contained in the keypad housings, such as printed circuit boards (PCBs). However, presently employed tamper-indicating structures may be sensitive to noises such as mounting surface conditions, the skill of an installer, the proper assembly of a tamper switch and keypad enclosure, and may even be unduly sensitive to external environmental and weather conditions. For example, upon the installation of a security interface device, such as a keypad, on a wall surface which is subject to uneven surface mounting properties, it is possible that a tamper post contained in the housing, wherein the tamper post is intended to be in contact with electronic circuitry on a printed circuit board located in the keypad housing may be offset and misaligned from a tamper switch on the printed circuit board subsequent to the installation of the keypad, thereby leading to potential tamper detecting malfunctions. Consequently, the personnel or installers which are engaged in mounting the security interface devices must be capable of properly implementing any necessary adjustments to either the security interface device or to the surface of the wall in order to be able to ensure the reliable functioning thereof in connection with the tamper-detecting mechanism subsequent to installation of the device. 
   Such tamper-detecting devices have heretofore been comprised of plastic or rubber posts or metallic spring members, which are mounted interiorly of the keypad housing and extend from the back housing portion forwardly into contact with a tamper switch or contact located on a printed circuit board contained within the keypad housing, whereby any attempt to pull the keypad device from the wall in an unauthorized manner will cause a disengagement between contacts formed by the tamper post or spring and a tamper switch mounted on the printed circuit board or to rupture a segment of the back housing mounting the tamper post, so as to produce a short circuit in the electronic system of the printed circuit board and to consequently trigger a signal raising an audible alarm and/or notifying a remote location which monitors the function of the keyboard or the security device, such as at an alarm company or law protective agency. 
   Moreover, this type of prior art structure, upon the unauthorized pulling off the front cover portion of the keypad housing, will trigger an alarm signifying that tampering has occurred, but is not adapted to provide a disconnection between the printed circuit board and the tamper post or spring which activates the tamper switch when the keypad housing is pulled away from the wall in its entirety, rather than merely the front housing part, unless the frangible segment of the back casing of the housing is ruptured, which segment is fastened to the wall, whereby the tamper post which is mounted on that segment and normally contacts the tamper switch on the printed circuit board, is concurrently pulled away from the printed circuit board so as to break contact therewith. This, of course, in due course requires replacement of the damaged rear portion of the keypad housing for reuse thereof. Thus, a good installation, which incorporates a tamper switch or mechanism utilized in the security interface device, such as a wall or surface mounted keypad, not only requires an assured reliability in reporting any tampering, but in addition to such functional requirements should also be cost effective in the manufacture, installation and utilization thereof in service over a lengthy service life. 
   2. Discussion of the Prior Art 
   Clark, U.S. Pat. No. 6,016,677 discloses a keypad for a door lock including a tamper detection and response feature whereby the unauthorized removal of a part or a front portion of the keypad, which forms a component of a deadbolt lock will activate a sensor switch utilized on a push/pull lock arrangement. This provides that the lock is automatically relocked when the mechanism is in a secured position, and in which whereby the system of the keypad provides for a remote enable and disable unit, directs a detection and a response unit, a low battery sensing arrangement, includes a bolt extension indicating feature and adjustable bolt throw feature. This is a relatively complex configuration, which does not readily lend itself to a simple tamper indicating switch mechanism which is incorporated in a wall or surface mounted keypad security device. 
   Magner, et al., U.S. Patent Publication No. 2005/0140496 A1 discloses a keypad and method providing for electronic access security and keyless entry of a vehicle. In that instance, there is disclosed a keypad for the keyless entry of the vehicle, including a coded arrangement. However, this particular structure does not incorporate a tamper-indicating feature analogous to that contemplated for by the present invention. 
   With regard to Hom, et al., U.S. Patent Publication No. 2003/0227766 A1, there is disclosed a keypad system including an illumination arrangement and light from LEDs which signify activation thereof. Again, there is no tamper indicating switch structure contacting a printed circuit board analogous to that employed in the present invention. 
   SUMMARY OF THE INVENTION 
   Accordingly, an advantage in the formation of a tamper switch installation in a wall or surface mounted keypad, which is highly efficient and reliable in operation while also concurrently being cost effective mounted, resides in the provision therein of a resilient rubber tamper switch, which possesses an electrically conductive end surface contacting a printed circuit board forming part of the operative system located within the keypad housing. The rubber tamper switch is normally in a compressed state upon the installation and mounting of the keypad on a surface or wall, in that in various embodiments of the invention, the tamper switch includes a rearwardly protruding portion, which is depressed upon the keypad being mounted on the wall or surface causing a constant contacting pressure to be exerted between the circuitry of the printed circuit board, which is fastened to the front cover of the keypad, and an electrically conductive end portion of the tamper switch during normal installation and operation of the keypad. Upon a tampering with the keypad by an unauthorized person, whereby the latter attempts to pull the front or cover portion of the keypad housing away from the back housing portion which is fastened to the wall or surface, this will cause the printed circuit board to be pulled forwardly, thereby enabling the compressed tamper switch, which is mounted to the interior of the housing back panel, to expand but lose contact of the conductive end thereof with the printed circuit board. The resultant short circuit or electrical malfunction will cause a signal to be generated and/or trigger an alarm at a remote monitoring installation or law enforcement agency, such as the police, indicative that a tampering action has been imparted to the keypad, and thereby alerting the appropriate authorities of that fact and to take protective steps. 
   Pursuant to another aspect of the present invention, upon the entire keypad housing being pulled from the wall as a integral unit, rather than merely the front or cover portion of the keypad housing being pulled away from the housing back panel, this will cause the tamper switch to also extend rearwardly and expand from its compressed state so as to cause the electrically conductive front end of the switch to lose contact with the printed circuit board, thereby also in this instance, resulting in the triggering of a signal or alarm indicative that tampering has taken place. 
   In accordance with a modified embodiment of the invention, wherein the keypad housing is mounted over an opening in the wall or surface, such as over a junction or switch box, or some other recess, there is provided a modified tamper switch configuration whereby the disengagement between the front and back panels of the keypad housing, such as a pulling away of the front or cover portion, will cause the compressed tamper switch to expand only forwardly from its mounted position in the rear panel, but to lose contact between the electrically conductive leading end thereof and the printed circuit board contained in the keypad housing, resulting in a short or malfunction and thereby again triggering a signal and/or raising an alarm at a monitoring location indicative that tampering with the keypad has taken place. 
   In order to achieve the maximum displacement for the tamper switch mechanism, the latter of which is constituted of a resilient material, such as rubber, and preferably of silicon rubber, which is highly resistant to deleterious and corrosive conditions while maintaining its elasticity and formative integrity, and wherein the tamper switch mechanism includes a leading end forming an electrically conductive surface for contacting a printed circuit board in the keyboard, such as being of a conductive metal, for instance, such as a gold plated copper or the like, or a conductive rubber or plastic composition, while imparting a high degree of flexibility and compressibility to the tamper switch mechanism. This preferred silicon rubber material also provides a high degree of flexibility when mounting the keypad possessing a rearwardly protruding tamper mechanism on an uneven surface or wall, thereby avoiding tamper switch offsets and misalignments with the PCB during installation of the keypad. Furthermore, utilizing silicon rubber for the tamper switch exhibits excellent resistance to compression set at room temperature, high and low temperature stability and resistance to deleterious chemical and weather conditions. Through the invention, there is an important cost savings involved when replacing presently employed tamper switches and eliminating a mounting screw which is employed in the connection of the frangible segment portion of the back housing panel in order to enable the segment to be broken away when pulling the keypad from a surface on which it is mounted, by the action of an unauthorized person. Pursuant to the invention, the mounting screw and the frangible segment portion are eliminated by employment of the novel rubber tamper switch design, thereby saving time for installers by an error proof alignment of the keypad components. 
   In essence, upon the installer completing the necessary wiring of the printed circuit board for activating an operation of the keypad, as is well known in the security device technology, by enclosing the front housing panel or cover and attaching it to the back panel of the keypad housing, the printed circuit board, the latter of which is located and mounted within the front cover portion of the keypad housing, makes contact with a conductive leading end pad which is mounted or molded on the compressible rubber switch and compresses the rubber shaft of the latter. The printed circuit board circuitry contact is now shorted with the conductive pad of the switch, and the compressed switch shaft applies contact pressure between the printed circuit board and the switch conductive pad during the entire period of time while the keypad is in its proper installed and operative state. 
   Upon an intruder unauthorizedly opening the front cover portion of the keypad housing which mounts the printed circuit board therein, while the security device is in activated service, the printed circuit board contact is separated from the electrically shorting conductive pad which is mounted at the end of the shaft of the rubber tamper switch and resultingly causes the security interface device to send out a signal indicative of a tampering attempt having taken place. Furthermore, in a tampering attempt, when the intruder rather than removing the front cover portion of the keypad housing, removes or pulls the entire device while intact from the surface on which it is mounted, the rubber switch also returns to the normal extended condition thereof, and causes the conductive pad on the shaft of the switch to be separated from the printed circuit board contact, thereby again causing the security interface device to transmit a signal indicative of a tampering having taken place. 
   Accordingly, it is an object of the present invention to provide a novel tamper switch mechanism for utilization in a security interface device, such as in a keypad. 
   Another object of the present invention is to provide a resilient or compressible tamper switch, which is mounted in a keypad housing and is in normal electrical contact with a printed circuit board and operative mechanism in the keypad housing in a compressed state and which will expand upon the unauthorized removal of the keypad housing from its mounting or the unauthorized removal of the front cover portion of the keypad housing, thereby breaking contact with the printed circuit board and emitting a tamper indicating signal. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Reference may now be made to the following detailed description of preferred embodiments of the invention, taken in conjunction with the accompanying drawings; in which: 
       FIG. 1  illustrates a front view of a security interface device in the form of a keypad; 
       FIG. 2  illustrates a perspective rear view of the device of  FIG. 1 ; 
       FIG. 3  illustrates a sectional view taken along line  3 - 3  in  FIG. 1 ; 
       FIG. 4  illustrates an enlarged detailed view of the encircled portion A in  FIG. 3 ; 
       FIG. 5  illustrates a sectional view taken along line  5 - 5  in  FIG. 1 ; 
       FIG. 6  illustrates an enlarged detailed view of the inventive tamper switch, similar to  FIG. 4 , shown in an installed wall mounted position of the device; 
       FIG. 7  illustrates a perspective view of the novel tamper switch; 
       FIG. 8  illustrates a front view of the tamper switch; 
       FIG. 9  illustrates a front view of the tamper switch showing in a compressed condition similar to that of  FIG. 6 ; 
       FIG. 10  illustrates a sectional view of the tamper switch with an extension plate mounted thereon; 
       FIGS. 11 ,  12 ,  13  and  14  illustrate respectively perspective, front, sectional and compressed sectional views of a modified tamper switch pursuant to the invention; 
       FIG. 15  illustrates the tamper switch of  FIG. 11 , as shown installed in a keypad; 
       FIG. 16  illustrates the tamper switch similarly to  FIG. 15 , but with the keypad shown mounted on a wall surface; 
       FIG. 17  illustrates a sectional view of the tamper switch shown with an extension plate mounted thereon; 
       FIG. 18  illustrates a sectional view similar to  FIG. 3  showing a modified tamper switch installed in the keypad, while mounted on a wall; 
       FIG. 19  illustrates an enlarged detailed view of the encircled portion B in  FIG. 18 ; and 
       FIGS. 20-22  illustrate, respectively, perspective and sectional views of the tamper switch, as utilized in  FIGS. 18 and 19 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now in specific detail to  FIGS. 1 to 5  of the drawings,  FIG. 1  illustrates a front view of a security interface device in the form of a keypad  10 , which is adapted to be normally mounted on a vertical surface or wall  12 , for example, as shown in  FIG. 5  of the drawings. As illustrated, the keypad  10  contains the usual operating components including electronics and a printed circuit board  14  mounted therein. An array of touch keys  16  for imparting an operational activity code conjunction with a monitoring system (at a remote location), such as may be located at a burglar and fire alarm company or a law enforcement agency, for example, a local police station or precinct. The keys  16  may be activated by means of a touch control, or by means of a heat sensitive screen or panel, as is well known in the technology. The electronics and operating components housed within an essentially rectangular keypad housing, although other shapes are contemplateable, the latter of which may be comprised of or molded from a rigid plastic material, and which includes a rear closure casing or panel structure  18 , as shown in  FIG. 2  of the drawings, including screw-receiving apertures  20  for mounting the panel or the rear closure structure  18  to the upright wall or surface  12 . Attachable to the rear casing structure  18  is a front housing cover member  22 , which may include a bottom-hinged cover portion  24 , adapted to be temporarily opened to enable access to the touch keys  16  for the inputting of coding information in order to either activate or deactivate the keypad and the alarm system, and closed at other times. The front cover or casing member  22  of the housing may also include a window opening  26  to enable a display of information as to whether the keypad system is activated or deactivated, and as to which particular locations on the premises are in a secured condition. 
   In essence, the keypad structure  10 , as described herein to this point is well known in the technology, and such keypads, which are configured in essentially rectangular casings of varied sizes and colorations, although other shapes, such as round, can also be considered, and molded from plastic materials or metals are widely employed and installed in homes, apartments, offices, manufacturing facilities, and in the most diverse locations where it is desired to provide for a degree of security against break-ins, tampering or unauthorized entry, while concurrently affording operative communication with a monitoring system for fire and smoke detection, in addition to a burglar alarm, as may be desired by a particular user of the keypad. Generally, the interior operative structure, including the printed circuit board  14 , which mounts or includes electronic circuitry for activating or deactivating the keypad functions is fastened to the interior  28  of the front cover member or casing  22  of the keypad housing, and is adapted to be detachably fastened to the rear closure panel or closure casing  18 , which mounts the entire keypad housing containing the keypad operating arrangements to the wall or surface structure  12 , as shown in  FIG. 5  of the drawings. 
   In order to provide a clear indication and information as to unlawful tampering or attempt of tampering having taken place with the keypad  10 , while the latter is mounted on the wall  12  and in an operative or so-called “armed” condition, and to possibly trigger an audible alarm at the site of the keypad installation and/or a signal at a remotely located monitoring installation, such as an alarm company or law enforcement authorities, pursuant to the invention there is provided a tamper switch mechanism in the keypad. This mechanism, in one embodiment of the invention, will provide a clear indication as to an occurrence of tampering upon either the unauthorized pulling away or removal of the front housing cover and casing member  22  of the keypad  10  from the wall-mounted rear or back housing casing  18 , which is attached to the wall, or, alternatively, the indication of an attempt to pull the intact entire keypad arrangement  10  from the mounting thereof on the wall  12 . 
   In order to impart this particular function, as shown in  FIGS. 3 through 10  of the drawings, there is provided a generally elastic or resiliently compressible tamper switch  30 , which, as detailed in  FIGS. 7 to 10 , includes an elongated preferably cylindrical shaft or post  32  having an annular flange  34  at proximate one end and a preferably cylindrical projection  36  projecting beyond the flange. The flange  34  is connected to the projection  36  by means of a thin frusto-conical web structure  38  surrounding the former and located intermediate the switch ends. This enables the tamper switch  30  to be resiliently compressed and effectively shortened when axial pressure is applied thereto, as shown in  FIG. 9  of the drawings. In order to render this compressive shortening further feasible, a hollow  40  may be provided to extend through the shaft portion  32  of the tamper switch  30  in a somewhat diamond cutout shape, to enable the shaft  32  to be also compressed in addition to compression-of the thin frusto-conical web structure  38  connecting  34  and  36 , thereby enabling the entire switch structure to be axially compressed when installed, for a purpose as described hereinbelow. 
   Preferably, although not necessarily, the entire tamper switch, as shown in  FIGS. 7-10 , may be constituted of an electrically non-conductive or dielectric silicon rubber, although a natural rubber or other suitable resiliently compressible material, which is substantially impervious to deleterious environmental, weather and temperature conditions, so as to impart a long service life thereto, is employable in connection with the invention. 
   At the end of the shaft portion  32  distant from projection  36 , there is mounted or molded thereon a circular pad  42  constituted of an electrically-conductive material, preferably but not necessarily such as gold plated copper, or a carbon impregnated silicon rubber or any other suitable electrically-conductive metal. 
   Implementing an installation of the tamper switch  30  in the keypad housing  10 , as shown in  FIGS. 2 ,  3  and particularly  FIG. 4 , the cylindrical projection  36  is adapted to extend rearwardly and outwardly of an aperture  46  formed in the back panel or casing  18  of the keypad housing, the annular flange  34  biasing against an inner ring-shaped sleeve member  48  of casing  18 , and with the end mounting the electrically-conductive pad  42  being at a short distance or gap  50  from an electrical circuit  52  on the printed circuit board  14 . In effect, in an uncompressed state, as shown in  FIG. 2 to 4  of the drawings, when the tamper switch  30  is positioned on the member  48  within the housing of the keypad  10 , the electrically-conductive pad  42  on the shaft or post  32  end facing the printed circuit board  14  forms a gap  50  and may either short or cause a malfunction of the circuit  52 , while the projection  36  distal thereto extends outwardly from the outer surface of the back panel or casing  18  of the keypad housing  10  in an armed condition of the keypad. 
   Upon the keypad  10  being mounted to a wall or surface  12 , as shown in  FIGS. 5 and 6  of the drawings, the attachment of the rear or back housing casing  18  to the wall imparts an axial compressive force to the projection  36  of the tamper switch  30 , forcing the projection  36  forwardly into the keypad housing  10 , with the flange  34  being pressed against the surface of the ring-shaped member  48 , and thereby resultingly compressing the thin frusto-conical web structure  38 , and possibly also the shaft portion  32 , as shown in  FIG. 9  of the drawings, thereby axially compressing and shortening the length of the tamper switch  30 . This causes the electrically conductive pad  42  to be in firm electrically-conductive contact with the circuitry  52  on the printed circuit board  14 , thereby closing the circuit, and rendering the entire structure to be in condition for proper operation upon the front cover member  22  being mounted and fastened to the back panel or casing  18  of the keypad housing  10 . 
   As can be readily ascertained, the cylindrical projection  36  of the tamper switch  30  which extends rearwardly outwardly of the rear casing  18  of the keypad housing  10  is of a sufficient axial length so as to be able to compensate for any irregularities present in the wall surface  12  on which the keypad  10  is mounted. However, in the event that such wall irregularities are more extensive in nature, then as shown in  FIGS. 7 and 10  of the drawings, an extension plate  60  having a shaft portion  62  may be mounted on the projection  36  of the tamper switch, with a hollow being formed in the projection  36 , which is adapted to engagingly receive shaft portion  62 . This extension plate  60 , which increases the length of the tamper switch  30  can also be molded onto the projection  36 , if desired. 
   When the keypad  10  is in operation, i.e., has been activated or “armed”, in the event that an unauthorized person or intruder pulls the front cover member  22  of the keypad housing  10 , which has the printed circuit board  14  fastened to the interior thereof, away from the back casing  18 , which is fixedly mounted to the wall, the compressed web structure  38  and switch shaft  32  will expand by the compressive force having been lifted, as shown in  FIG. 4 , but will form gap  50  between the conductive pad  42  at the inner end of the switch to and the circuit  52  on the printed circuit board  14 , thereby either causing a short or a malfunction to be affected in the circuit  52 , and resultingly triggering an alarm and/or transmitting a signal indicating that the keypad  10  has been subjected to tampering by an intruder. 
   Furthermore, in the event that the keypad housing  10  is pulled away in its entirety by an unauthorized person or intruder from the wall or surface  12  on which it is mounted, without separation between casing parts  18  and  22 , while the keypad is in an activated condition, the projection  36  will expand rearwardly and also permit for expansion of the tamper switch web  38 , which, in essence, will also create a gap  50  between the electrically-conductive pad  42  at the leading end of shaft or post  32  and circuit  52  on the printed circuit board  14 , as shown in  FIG. 4 , and thereby trigger an alarm and/or signal which can be transmitted to an appropriate alarm monitoring facility or law enforcement authority in order to alert them or other agencies involved with maintaining the integrity of the security system. 
   In a modified embodiment, wherein the basic operation of a tamper switch  70  is essentially similar to that as previously described, and wherein similar components are identified by the same reference numerals, in that instance, the tamper switch  70  has been somewhat modified in its configuration, as shown in  FIGS. 11 to 17  of the drawings. In this instance, the compressively resilient or rubber shaft portion  72 , as shown in the drawings, is connected to a projection  74 , which is adapted, as heretofore, protrudes from the back panel  18  of the keypad housing  10  prior to being mounted to a rear wall  12 , such as shown in  FIG. 16  of the drawings. As previously stated, the projection  74  includes a hollow  76  which may be adapted to receive an extension pad  78 , as shown in  FIG. 17 , to compensate for excessive irregularities in the wall mounting surface  12 . An annular ring-shaped flange  80  is connected to the projection  74  by means of a thin, flexibly resilient frusto-conical annular web structure  82 , the latter of which is compressible, as shown in  FIG. 14  of the drawings, when the tamper switch  70  is installed and compressed upon mounting the keypad  10  on an upright surface or wall  12 , as shown in  FIG. 16  of the drawings. In this instance, although the function of the tamper switch  70  is identical to that of switch  30  as in the previous embodiment, in this instance; however, the configuration of the tamper switch  70  is somewhat different in that the shaft portion  72  does not possess a through aperture (such as aperture  40  in switch  30 ) and is not compressible in a manner analogous to that as in the first embodiment. However, in this embodiment, the connection between the shaft portion  72  and the projection  74  is provided by a resiliently flexible annular segment  77 , which is also of a frusto-conical configuration. Consequently, the axial expansion and compression of switch  70  is provided for by both of the frusto-conical annular segment  77  and web structure  82 , as shown in  FIGS. 14 and 16  of the drawings. For the remainder, the function and structure of the keypad  10  is identical to that of the preceding embodiment and need not be repeated herein. However, in this embodiment, a primary distinction resides in that the deflection is provided for by a combined compression of the frusto-conical annular segment  77  and the web  82 , rather than the potentially dual compressive action afforded by the tamper switch  30  of the previous embodiment, in which both the annular frusto-conical web  38  and the shaft portion  32  containing aperture  40  are compressible upon installation and mounting the keypad  10  on a wall or surface  12 . 
   In the event that the keypad is mounted on a wall  12 , which does not provide for a contact surface behind a projection  36  or  74  of the tamper switch  30  or  70 , as in the previous embodiments, for example, when a tamper switch  90  is mounted over an opening in the wall or a deep cutout such as for a junction or switch box, in that instance, there is provided the tamper switch  90 , as shown in  FIGS. 18 to 22  of the drawings. In this instance, the tamper switch  90 , as shown particularly in detail in  FIGS. 20 to 22 , includes a cylindrical portion  92 , which is hollow in order to enable the mounting thereof on the cylindrical sleeve member  48  on the inner surface of the back panel  18  of the keypad housing  10 , and includes a short smaller cylindrical projection  94  attached thereto or integrally therewith with the interposition of resiliently compressible annular thin web  96 . The short cylindrical portion  94  has an electrically-conductive pad  98  on the surface thereof which faces towards the circuitry  52  printed circuit board  14 , which is mounted in the keypad  10 . In this instance, when mounted interiorly of the keypad housing in which the larger cylindrical portion is positioned on the guide sleeve member  48  in the back housing panel  18 , and the front cover member  22  is closed, a compressive force is imparted to the tamper switch  90  such that the electrically-conductive pad  98  is in contact with the printed circuit board  14 , thereby closing the circuit  52 . Accordingly, when an unauthorized person or intruder pulls the front cover member  22 , which has the printed circuit board  14  fastened thereto, away from the back panel which is fastened to the wall, this will form a gap  50  between the conductive pad  98  on the leading end of the tamper switch  90  and the circuit  52  on the printed circuit board  14 , causing either a short or malfunction in the circuit  52 , which will trigger an alarm and/or transmitting a signal signifying that an unlawful act has been committed by tampering with the keypad  10 . Again, as in the previous embodiment, this will generate a signal at a monitoring location or a law enforcement authority, and may concurrently trigger an audible alarm alerting the site as to the tampering action by the unauthorized person or intruder. 
   Although the tamper switches  30 ,  70  and  90 , as described herein, have been represented as consisting of cylindrical components, they may also be constituted as being polygonally-shaped in transverse cross-section, and the cylindrical shapes are not to be construed as being limiting in nature. 
   From the foregoing, it becomes clearly and readily apparent that the present invention is directed to a novel and economical structure for providing a tamper switch to produce a tamper resistant keypad, and whereby the tamper switch may be readily retrofitted on keypad structures which are currently in use. Concurrently, this invention, in the various embodiments thereof, enables the dual function of monitoring any tampering with a keypad in the event that either the front cover of the housing or casing is pulled away from a rear casing, while the latter remains fastened to the wall or mounting surface, or, alternatively, in case the keypad is pulled in its entirety away from its wall mounting position. 
   While the present invention has been particularly shown and described with respect to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in forms and details may be made without departing from the scope and spirit of the present invention. It is therefore intended that the present invention not be limited to the exact forms and details described and illustrated, but fall within the scope of the appended claims.