referring first to fig1 an alarm sensor in accordance with the present invention is generally designated by reference numeral 10 and shown in exploded form . a housing unit comprised of a housing base 12 and a housing cover 14 is shown . within housing base 12 and housing cover 14 is a printed circuit board 16 and a rotatable mounting disc 18 . although shown as coupled to mounting disc 18 , a first mounting pin 20 and a second mounting pin 22 are typically separate from mounting disc 18 and extend outwardly in generally opposite directions . printed circuit board 16 is shown as a pir sensor for illustrative purposes . thus , printed circuit board 16 includes a pir sensor element 24 and a pir lens 26 . also on printed circuit board 16 are terminal strips 28 and 30 . terminal strips 28 and 30 are preferably comprised of “ speaker - jack style ” terminals which simply snap down to secure connecting wires . thus , no terminal screws are necessary . in the instance where alarm sensor 10 is a pir sensor , housing cover 14 can also be split in two components to allow for dual focal lengths for the pir zones . dual focal lengths are often incorporated in pir sensors to eliminate false alarms due to pets . it will be noted by those skilled in the art that the mounting apparatus and method of the present invention can be utilized not only for pir sensors , but also for various security alarm sensors based on microwave technology , ultrasound technology , or any variations thereof . furthermore , the mounting apparatus and method of the present invention is equally applicable to alarm sensors for fire , smoke , temperature , etc . additionally , the mounting apparatus and method of the present invention can be utilized on hardwired or wireless sensors . thus , the actual components shown on printed circuit board 16 are only illustrative ; countless variations are possible . housing base 12 includes corner mount screw hole punch - outs 32 , 34 , 36 and 38 . an installer can selectively utilize screws through corner mount screw holes punch - outs 32 , 34 , 36 and 38 to mount housing base 12 onto corner walls 40 and 42 . similarly , housing base 12 illustrates four flat wall mount screw hole punch - outs 44 , 46 , 48 and 50 . an installer will selectively utilize flat wall mount screw hole punch - outs 44 , 46 , 48 and 50 when the housing base is to be installed onto a flat wall . finally , housing base 12 also includes a swivel mount punch - out 52 that allows installation so that alarm sensor 10 can be made to slightly rotate . while the alternative utilization of corner mount screw hole punch - outs 32 , 34 , 36 and 38 ; flat wall mount screw hole punch - outs 44 , 46 , 48 and 50 ; or swivel mount punch - out 52 allows a single housing unit to be incorporated in various applications , a screwdriver is required for all installations . particularly when a corner mounting is desired , the use of screws and a screwdriver on a ladder is often burdensome . housing base 12 is adapted to receive rotatable mounting disc 18 , first mounting pin 20 , and second mounting pin 22 . more specifically , housing base 12 includes a first guided groove 54 , a second guided groove 56 , a first guide slot 58 and a second guide slot 60 . as best shown in fig2 first guide slot 58 permits a path upon which first mounting pin 20 can easily travel whereas second guide slot 60 permits a path upon which second mounting pin 22 can easily travel . based on the proper manipulation of rotatable mounting disc 18 by means of a screwdriver slot 62 , first mounting pin 20 can be made to either retract within or extend beyond a first opening 64 on housing base 12 . similarly , second mounting pin 22 can be made to either retract within or extend beyond a second opening 66 on housing base 12 . first opening 64 and second opening 66 are typically on respective planes 65 and 67 of housing base 12 which are contoured at approximately 45 ° angles . this angle permits planes 65 and 67 to rest flatly on corner walls 40 and 42 that generally form a 90 ° angle . this flush alignment is best seen in fig3 . before addressing the interconnection between rotatable mounting disc 18 and housing base 12 , and the manipulation of mounting disc 18 to control the selective movement of first mounting pin 20 and second mounting pin 22 , it should be understood that alarm sensor 10 is typically packaged as a interconnected unit . housing base 12 is snapped together to housing cover 14 with circuit board 16 and mounting disc 18 therein . in order to separate housing base 12 from housing cover 14 , a screwdriver is typically inserted into a slot 68 to release a mounting tab ( not shown ) that holds housing unit 12 and housing base 14 together . at this stage , printed circuit board 16 is coupled to housing base 12 by means of a circuit board height index tab 70 . when slight pressure is applied to circuit board height index tab 70 , circuit board 16 can be easily removed . circuit board 16 can be wired at this point so that when ultimately replaced within housing base 14 , the wires can be easily displaced through the housing unit by means of a wire entry punch - out 72 . obviously , wireless sensors would not require wire entry punch - out 72 . once housing base 12 and housing cover 14 have been separated and circuit board 16 has been removed , housing base 12 is ready for mounting to walls 40 and 42 . an installer will simply hold housing base 12 at a desired location , insert a screwdriver into screwdriver slot 62 and turn rotatable mounting disc 18 approximately 45 °. the rotational movement of mounting disc 18 will result in first mounting pin 20 and second mounting pin 22 simultaneously moving outwardly so as to sufficiently pierce walls 40 and 42 and secure housing base 12 in place . at this point , printed circuit board 16 would be reconnected to housing base 12 by manipulating circuit board index tab 70 and housing cover 14 would be snapped onto housing base 12 . fig2 - 6 will assist demonstrating precisely how rotational movement of mounting disc 18 results in appropriate linear movement of first mounting pin 20 and second mounting pin 22 to selectively , but securely , attach alarm sensor 10 to corner walls 40 and 42 . as seen in fig2 rotatable mounting disc 18 includes optional directional arrows 74 and 76 to instruct an installer in the direction rotatable mounting disc 18 should be rotated to connect housing base 12 to walls 40 and 42 . fig2 demonstrates the position wherein rotatable mounting disc 18 has already been turned clockwise so that first mounting pin 20 and second mounting pin 22 extend outwardly from housing base 12 . instead of utilizing a screwdriver in screwdriver slot 62 , it may be possible to utilize thumb turns 78 and 80 to rotate mounting disc 18 . in the preferred embodiment of the present invention , a mechanism has been provided to prevent over - rotation of mounting disc 18 which would cause damage to first mounting pin 20 and second mounting pin 22 . referring to fig4 it is shown that rotatable mounting disc 18 includes a first protruding knob 82 and a second protruding knob 84 . first protruding knob 82 travels along first guided groove 54 whereas second protruding knob 84 travels along second guided groove 56 . a first non - protruding engagement end 86 of first mounting pin 20 rests loosely between first protruding knob 82 and a raised portion of mounting disc 18 . similarly , a second non - protruding engagement end 88 of second mounting pin 22 rests loosely between second protruding knob 84 and a raised edge of mounting disc 18 . first non - protruding engagement end 86 and second non - protruding engagement end 88 preferably extend at approximately 90 ° angles respectively from the rest of first mounting pin 20 and second mounting pin 22 . [ 0026 ] fig4 shows the back of housing base 12 and mounting disc 18 in a position wherein first mounting pin 20 and second mounting pin 22 are retracted within housing base 12 . conversely , fig5 shows the back of housing base 12 and mounting disc 18 in a position wherein first mounting pin 20 and second mounting pin 22 are extended beyond housing base 12 . this difference is caused by an approximately 45 ° turn of mounting disc 18 from the inside of housing base 12 . as shown in fig4 and fig5 mounting disc 18 has been connected to housing base 12 by pressure mounting tabs 90 , 92 , 94 and 96 . while experimentation has shown that mounting disc 18 is most securely attached to housing base 12 by utilizing four pressure mounting tabs , it is also possible to use two pressure mounting tabs . the utilization of pressure mounting tabs is preferred since , should mounting disc 18 break it is easy to attach a new one to the existing housing base without replacing the entire housing unit . however , there are many alternative techniques of connecting mounting disc 18 to housing base 12 that will become apparent to those skilled in the art . [ 0027 ] fig6 is a cross - sectional view of fig5 taken along reference line 6 - 6 and effectively shows the different components and shapes of components utilized in the preferred embodiment of the present invention . of significant importance in the preferred embodiment is the fact that not only can housing base 12 be easily installed to corner walls 40 and 42 , but , should the installer have made an error , the device is as easily removable and reinstalled at a new position . the pins are sufficiently narrow so as to cause only negligible damage to any wall . whether rotating mounting disc 18 to either retract or extend first mounting pin 20 and second mounting pin 22 , first guided groove 54 and second guided groove 56 prevent over - rotation of mounting disc 18 in any direction . thus , any potential damage to first mounting pin 20 and second mounting pin 22 is eliminated . although , through experimentation , the rotation of mounting disc 18 has been shown to be the best mode for achieving selective linear movement of first mounting pin 20 and second mounting pin 22 from a first retracted position to a second extended position , the utilization of other means is also foreseen . for instance , the mounting pins can be selectively moved by means of a thumb - controlled , ratcheted device similar to a smaller version of a car jack , by a geared wheel - turn , by a locked collar apparatus , or by other means known in the art for applying sufficient and selective torque to the mounting pins . the various means for achieving selective , linear movement of the mounting pins should be sufficiently small so as not to interfere with the replacement of the printed circuit board on the housing base . it will be apparent from the foregoing description that the present invention provides a new and improved method and apparatus for providing an easy connection of an alarm sensor to the corner of a room with minimal risk to the circuitry and without utilizing of any screws , nails or mounting brackets . while a specific preferred embodiment has been described , many variations may be utilized . for instance , although both first mounting pin 20 and second mounting pin 22 have been shown to incorporate only a single prong , double pronged pins ( similar to staples ) can be incorporated . additionally , first mounting pin 20 and second mounting pin 22 can be threaded pins in certain variations . moreover , while rotatable mounting disc 18 has been shown as being generally circular and of a composite material , it can indeed take various shapes as long as its rotational movement will result in basic linear movement of first mounting pin 20 and second mounting pin 22 . while there has been shown and described what is presently considered to be the preferred embodiment of this invention , it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the broader aspects of this invention . for instance , the preferred embodiment has described a single rotatable mounting disc 18 , which upon proper manipulation , simultaneously moves both first mounting pin 20 and second mounting pin 22 . it is certainly foreseen that separate mounting discs could be utilized for each mounting pin , particularly if the device is wide . moreover , while a particular means for separating the housing base from the housing cover and the printed circuit board from the housing base has been shown , many variations exist in the art . it is , therefore , aimed in the appended claims to cover all such changes and modifications as fall within the true scope and spirit of the invention .