Abstract:
An alarm for a door is operable to generate an alarm signal when a rotary grip member of the door is rotated to a particular position, such as an unlocked position. The alarm comprises a housing having a strap retainer configured to receive and retain a strap to hold the housing to the rotary grip member. The alarm comprises a tilt switch for switching when the housing is tilted. Control circuitry is interconnected to the tilt switch and to an annunciator and is operable to activate the annunciator dependent on a state of the tilt switch.

Description:
FIELD 
       [0001]    The present invention relates to alarms, and in particular, to alarms for rotary door hardware, such as for the thumb turns of door locks. 
       BACKGROUND 
       [0002]    Various types of alarms exist to protect against unauthorized or undetected access to secured premises. Some such alarms may be installed on a knob of a door. Typically, such alarms include a switching mechanism to activate an auditory alarm signal when the door is opened. Unfortunately, conventional alarms may be difficult to install, only work in a single orientation, or provide limited information to the user. 
       SUMMARY 
       [0003]    In an aspect, an alarm for a door having a rotary grip member is disclosed, comprising a housing having a strap retainer configured to receive a strap; a tilt switch supported by the housing for switching when the housing is tilted; an annunciator; control circuitry interconnected with the tilt switch to receive an input signal from the tilt switch, the control circuitry operable to activate the annunciator dependent upon a state of the tilt switch; a strap for retention by the strap retainer to strap the housing to the rotary grip member so that the housing rotates with the rotary grip member. 
         [0004]    In another aspect, an alarm for a door having a rotary grip member is disclosed, comprising a housing having a strap retainer configured to receive a strap; a tilt switch supported by the housing for switching when the housing is tilted; an annunciator; control circuitry interconnected with the tilt switch to receive an input signal from the tilt switch, the control circuitry operable to activate the annunciator dependent upon a state of the tilt switch; a strap extending around the rotary grip member and retained by the strap retainer, said strap holding the housing to the rotary grip member so that the housing rotates with the rotary grip member. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    In the figures, which illustrate example embodiments: 
           [0006]      FIG. 1  is a perspective view of a door alarm installed on a door lock; 
           [0007]      FIG. 2  is a top view of the door alarm of  FIG. 1 ; 
           [0008]      FIG. 3  is a rear cross-sectional view of the door alarm of  FIG. 1 , along line  3 - 3  shown in  FIG. 2 ; 
           [0009]      FIG. 4  is a cross-sectional view of the door alarm of  FIG. 1 , along the line  4 - 4  shown in  FIG. 2 ; 
           [0010]      FIG. 5  is a cross-sectional view of the door alarm of  FIG. 1 , along the line  5 - 5  shown in  FIG. 2 , with the door alarm in a first orientation; 
           [0011]      FIG. 6  is a further cross-sectional view of the door alarm of  FIG. 1 , along the line  5 - 5  shown in  FIG. 2 , with the door alarm in a second orientation; 
           [0012]      FIG. 7  is a schematic block diagram of components of the door alarm of  FIG. 1 ; 
           [0013]      FIG. 8  is a cross-sectional view of another door alarm in a first orientation; 
           [0014]      FIG. 9  is a cross-sectional view of the door alarm of  FIG. 8  in a second orientation 
           [0015]      FIG. 10  is a perspective view of another door alarm installed on a door lock; 
           [0016]      FIG. 11  is a side view of another door alarm installed on a door lock; and 
           [0017]      FIG. 12  is a perspective view of the door alarm of  FIG. 11 ; 
           [0018]      FIG. 13  is a cross-sectional view of another door alarm; 
           [0019]      FIG. 14  is a top view of another door alarm; 
           [0020]      FIG. 15  is a cross-sectional view of the door alarm of  FIG. 14  along line  15 - 15 ; 
           [0021]      FIG. 16  is a perspective view of another door alarm installed on a door lock; 
           [0022]      FIG. 17  is a top view of the door alarm of  FIG. 16 ; 
           [0023]      FIG. 18  is a rear view of the door alarm of  FIG. 16 , along line  18 - 18  shown in  FIG. 17 ; 
           [0024]      FIG. 19  is a cross-sectional view of the door alarm of  FIG. 16  along the line  19 - 19  shown in  FIG. 17 ; 
           [0025]      FIG. 20  is a cross-sectional view of the door alarm of  FIG. 16 , along the line  20 - 20  shown in  FIG. 17 , with the door alarm in a first orientation; and 
           [0026]      FIG. 21  is a further cross-sectional view of the door alarm of  FIG. 16 , along the line  20 - 20  shown in  FIG. 17 , with the door alarm in a second orientation. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]      FIG. 1  depicts a door alarm  100 . Door alarm  100  includes a housing  102 , adapted for mounting to a rotary actuator of a door, e.g. a grip member such as thumb turn  104  of a door lock  106  in door  108 . 
         [0028]    In conventional fashion, door lock  106  has a dead bolt  110 , connected to thumb turn  104  such that rotation of thumb turn  104  in a vertical plane as indicated by arrow A causes dead bolt  110  to extend or retract from door  108  as indicated by arrow B. Thumb turn  104  has a locked position and an unlocked position. When thumb turn  104  is in its locked position, dead bolt  110  is extended. When thumb turn  104  is in its unlocked position, dead bolt  110  is retracted. As depicted in  FIG. 2 , in its locked position, thumb turn  104  is oriented substantially horizontally. In its unlocked position, thumb turn  104  is oriented substantially vertically. Thumb turn  104  extends from the surface of door  108  to allow manual operation by a user. 
         [0029]    As will be appreciated, in other embodiments, housing  102  and thumb turn  104  may be oriented vertically in the locked position and horizontally in the unlocked position. 
         [0030]    Referencing  FIG. 3  along with  FIG. 1 , housing  102  of door alarm  100  is generally rectangular and has front, top and bottom and side walls. The rear of housing  102  is open so that door alarm  100  may be installed on door lock  106  by positioning housing  102  over thumb turn  104  so that thumb turn  104  is received in the rear of housing  102  and abuts four anchor posts  124  on housing  102 . Anchor posts may be formed, for example, from metal plastic or wood and may be coated with a soft or tacky material such as rubber, silicone or the like, which may promote frictional engagement between thumb turn  104  and anchor posts  124 . Housing  102  is securely held to thumb turn  104  by adjustable straps  112 . 
         [0031]    Strap retainers  118  are formed on housing  102  to hold straps  112  in place. In the depicted embodiment, housing  102  has two pairs of strap retainers  118 , each pair comprising a strap retainer  118  on the top wall of housing  102  and a strap retainer on the bottom wall of housing  102 . Each pair of strap retainers  118  holds a strap  112 , with each end of the strap  112  being received in one strap retainer  118  of the pair. Each of strap retainers  118  has an internal pawl, indicated generally at  111 . Straps  112  have ends  117  with teeth  119  which interlock with the pawls to define a ratchet mechanism between straps  112  and retainers  118  which allows the ends of straps  112  to be pulled through retainers  118  to tighten the straps  112 , but prevents reversing (loosening of the straps). Straps  112  may therefore be tightened to pull against the strap retainers  118 , urging housing  102  against thumb turn  104 . 
         [0032]    Tightening of straps  112  urges housing  102  against thumb turn  104  so that thumb turn  104  and anchor posts  124  bear against one another. Conveniently, strap retainers  118  prevent loosening or removal of straps  112  so that housing  102  cannot be removed from thumb turn  104  without breaking straps  112 . Straps  112  may be formed of a tough nylon or plastic which can be cut with a blade, but with sufficient tensile strength so that a strap  112  cannot easily be broken by hand. Accordingly, once door alarm  100  is installed and secured with straps  112 , it cannot easily be removed without a strap cutting tool. 
         [0033]    It will be appreciated that a user may carry several sets of straps to allow re-use of the door alarm on different doors when, for example, the user is travelling. 
         [0034]    As seen in  FIG. 2 , thumb turn  104  is formed at the end of a shaft  120  which extends into door  108  to operate the mechanism of lock  106  when thumb turn  104  is turned by a user. A small gap exists between door  108  and the rear surface  116  ( FIG. 3 ) of thumb turn  104 , which accommodates straps  112 . As depicted, straps  112  hold housing  102  against thumb turn  104  so that the rear edge of housing  102  is approximately flush with rear surface  116  of thumb turn  104 . However, as will become apparent, in other embodiments, thumb turn  104  may protrude from the rear edge of housing  102  or the rear edge of housing  102  may extend past thumb turn  104 . 
         [0035]      FIG. 3  depicts door alarm  100  and thumb turn  104  in rear cross-sectional view along lines  3 - 3  shown in  FIG. 2 . Housing  102  has an interior transverse wall  122 , with four anchor posts  124  extending diagonally therefrom towards thumb turn  104 . 
         [0036]    As is best shown in  FIG. 4 , anchor posts  124  extend diagonally from wall  122  and define a notch into which thumb turn  104  is received. Straps  112  squeeze thumb turn  104  against anchor posts  124 , securing engagement of door alarm lock  100  to thumb turn  104 . 
         [0037]    Referencing  FIGS. 4 and 5 , housing  102  of door alarm  100  also has a circuit board  123 , extending from transverse wall  122  to a front wall  114  of housing  102 . Mounted to circuit board  123  are a battery holder  126  holding a battery  128 , two tilt switches  130 - 1  and  130 - 2  (individually and collectively, tilt switches  130 ), a control unit  134 , and light and audio annunciators, namely, speaker  132  and light-emitting diode (LED)  136  and a wireless transceiver  142 . As depicted, control unit  134  and wireless transceiver  142  are formed as separate chips. However, in some embodiments, control unit  134  and wireless transceiver  142  may be modules of a single chip. Door alarm  100  is also equipped with a power switch  138 , mounted to circuit board  123 . 
         [0038]    Battery  128  may be any suitable type and size of battery, such as a 9V, C, D, AA, or AAA alkaline or lithium-ion cell or the like. Battery  128  may be single-use or rechargeable. In some embodiments, battery  128  may comprise multiple cells connected in series or parallel. Battery holder  126  is configured to securely hold battery  128  to circuit board  123  and thus, to housing  102  and electrically interconnect battery  128  to the alarm circuit. Front wall  114  of housing  102  has a hinged door portion  115  to allow access to battery holder  126  and battery  128 . Battery  128  may be replaced by lifting door portion  115 . In other embodiments, door  115  is removable, rather than being hinged. 
         [0039]    Each of tilt switches  130 - 1 ,  130 - 2  has a set of electrical contacts and a movable element  131  which moves under the influence of gravity to close (turn ON) the switch in a first orientation and to open (turn OFF) the switch in a second orientation. When gravity pulls the movable element in the direction indicated by arrow O in  FIG. 5 , the switch is opened (turned OFF). Conversely, when gravity pulls the movable element in the direction of arrow C, the switch is closed (turned ON). Tilt switches  130 - 1 ,  130 - 2  extend at approximately a 90-degree angle to one another. With door alarm  100  installed, tilt switches  130 - 1 ,  130 - 2  are each oriented in a vertical plane parallel to the plane of rotation of thumb turn  104 . In the position shown in  FIGS. 1-5 , thumb turn  104  is oriented substantially horizontally, and each of tilt switches  130 - 1  and  130 - 2  extends upwardly at an angle of approximately 45 degrees to the vertical. In this position, both tilt switches  130 - 1  and  130 - 2  are closed (turned ON). Conversely, when thumb turn  104  and housing  102  are rotated to a vertical orientation, one of tilt switches  130 - 1  and  130 - 2  extends downwardly at an angle of approximately 45 degrees to the vertical and is pulled open (turned OFF) by gravity. For example, as depicted in  FIG. 6 , housing  102  is rotated 90 degrees counter-clockwise relative to its position in  FIG. 5 , and tilt switch  130 - 1  is pulled open (turned OFF). If, alternatively, housing  102  were rotated 90 degrees clockwise from the position shown in  FIG. 5 , tilt switch  130 - 2  would be pulled open (turned OFF). If housing  102  were rotated 180 degrees from the position shown in  FIG. 5 , both of tilt switches  130 - 1 ,  130 - 2  would be pulled open (turned OFF). Thus, the states of tilt switches  130  are indicative of the position of housing  102  and thumb turn  104 . When housing  102  and thumb turn  104  are oriented horizontally, both of tilt switches  130 - 1 ,  130 - 2  are in the same state (ON or OFF). When housing  102  and thumb turn  104  are oriented vertically, tilt switches  130 - 1 ,  130 - 2  are in different states (one ON, one OFF), 
         [0040]    Speaker  132  is a conventional low-power speaker. Speaker  132  is sufficiently powerful to produce an audible alarm signal when powered. Speaker  132  may, for example, be adapted to emit a high-pitched tone or an oscillating siren signal when powered. 
         [0041]    Transceiver  142  includes an antenna and appropriate control circuitry. Transceiver  142  is adapted to send and receive messages in one or more protocols and on one or more frequency bands. Transceiver  142  may include for example, GSM/GPRS/3G, WI-FI, RF, Bluetooth or similar radios. 
         [0042]    Control unit  134  is an integrated circuit adapted to determine the state of tilt switches  130 - 1  and  130 - 2  and thus, the orientation of housing  102  and thumb turn  104  to which housing  102  is mounted. Control unit  134  includes a memory (not shown) with firmware installed thereon. The firmware provides logic functions for producing outputs of the door alarm by driving speaker  132 , LED  136  and transceiver  142  based on the determined states of tilt switches. 
         [0043]    Door alarm  100  also has mode selector buttons  139 - 1  and  139 - 2 , which are operatively mounted to circuit board  123  and protrude through front wall  114 . Mode selector buttons  139 - 1  and  139 - 2  are used to select a mode corresponding to the direction of rotation of housing  102  (clockwise or counter-clockwise) required to unlock lock  106 . 
         [0044]      FIG. 7  depicts a schematic block diagram of components of door alarm  100  Control unit  134  receives input signals indicative of the states of each of tilt switches  130 - 1  and  130 - 2  and mode selector buttons  139 - 1  and  139 - 2 . In an example embodiment, each of tilt switches  130 - 1  and  130 - 2  and mode selector buttons  139 - 1  and  139 - 2  may be connected to a different digital input of control unit  134 , with LOW and HIGH digital signals on these inputs indicating the respective states of each switch. 
         [0045]    Based on these input signals, control unit  134  provides control signals to each of the annunciators (speaker  132  and LED  136 ) and to transceiver  142 . 
         [0046]    Control unit  134 , speaker  132 , LED  136  and transceiver  142  are powered by battery  128  ( FIG. 6 ). 
         [0047]    As noted, control unit  134  receives input signals indicating the states of each of tilt switches  130 - 1  and  130 - 2 , and thus, the orientation of housing  102  and thumb turn  104 . As is further described below, door alarm  100  is armed by powering on door alarm  100 , installing door alarm  100  on thumb turn  104 , turning thumb turn  104  to its locked position, and actuating one of mode selector buttons  139 - 1 ,  139 - 2  to indicate to control unit  134  the states of tilt switches  130 - 1 ,  130 - 2  when thumb turn is in each of its locked and unlocked positions. 
         [0048]    As will be appreciated, the states of tilt switches  130 - 1 ,  130 - 2  change as door alarm  100  is rotated in approximately 90-degree increments. Firmware of control unit  134  stores a sequence of states representing a progression of rotations in each direction. That is, when door alarm  100  is in a particular orientation, firmware in control unit  134  is able to determine the next state in a first direction (e.g., clockwise) and the next state in a second direction (e.g. counter-clockwise), which corresponds to the previous state in the first direction. 
         [0049]    Firmware of control unit  134  maintains a count of the number of times housing  102  and thumb turn  104  are moved to the unlocked position. Control unit  134  includes a reset trigger, to reset the count. For example, the count maintained by of control unit  134  may be reset when mode selector buttons  139 - 1  and  139 - 2  are toggled in a certain pattern. Additionally or alternatively, the counting circuitry may be reset when power is removed, i.e. when battery  128  is removed from holder  126 . 
         [0050]    Control unit  134  controls each of speaker  132 , LED  136  and transceiver  142  based on whether housing  102  and thumb turn  104  are in a locked or unlocked position and based on the count maintained in control unit  134 . 
         [0051]    In addition, control unit  134  may cause one or more of speaker  132 , LED  136  and transceiver  142  to emit a low battery warning signal when battery  128  is depleted to below a threshold level. 
         [0052]    In use, door portion  115  of front wall  114  is opened and battery  128  is installed in battery holder  126 . Door alarm  100  is powered on by actuating power switch  138 , accessed through the rear face of housing  102 . 
         [0053]    Door alarm  100  is installed on thumb turn  104  by positioning housing  102  over thumb turn  104 , with thumb turn  104  received in the rear of housing  102 . Straps  112  are looped around thumb turn  104  and ends  117  are received by strap retainers  118  of housing  102  and tightened. Straps  112  pull anchor posts  124  into snug engagement with thumb turn  104 , securing housing  102  to thumb turn  104 . Once door alarm  100  is installed on thumb turn  104 , power switch  138  cannot be accessed. Accordingly, door alarm  100  cannot be turned off without removing door alarm  100  from thumb turn  104 . 
         [0054]    Door alarm  100  is installed so that it is upright, with door portion  115  at the bottom of front wall  114 , when thumb turn  104  is in its horizontal, locked orientation. In this position, both tilt switches  130  are (ON). 
         [0055]    Mode selector buttons  139 - 1 ,  139 - 2  are used to indicate to control unit  134  the direction in which thumb turn  104  rotates to unlock. Thus, mode selector buttons  139 - 1 ,  139 - 2  indicate to control unit  134  the states of tilt switches  130 - 1 ,  130 - 2  when thumb turn  104  is in its unlocked orientation. 
         [0056]    To set the mode of door alarm  100 , door alarm  100  is powered on, installed on thumb turn  104 , and oriented in its locked position. One of mode selector buttons  139 - 1 ,  139 - 2  is pressed to indicate the direction in which thumb turn  104  rotates to reach the unlocked position. Control unit  104  reads the states of tilt switches  130 - 1 ,  130 - 2  and recognizes those states as being indicative of the locked position. Thus, the operation of mode selector buttons  139  and power switch  138  identify the locked state. One of mode selector buttons  139 - 1 ,  139 - 2  is pressed to indicate the direction in which thumb turn  104  rotates to reach the unlocked position. For example, mode selector switch  139 - 1  may be pressed to indicate a counter-clockwise turn to the unlocked position, or mode selector switch  139 - 2  may be pressed to indicate a clockwise turn to the unlocked position. Based on the measured state of tilt switches  130 - 1 ,  130 - 2  in the locked position and the selected direction of turning to the unlocked position, by reference to the sequence of states loaded in firmware, control unit  134  determines and stores the states of tilt switches  130 - 1 ,  130 - 2  which are indicative of unlocking. 
         [0057]    As noted, in the depicted embodiment, the locked position is as shown in  FIG. 5 , and the unlocked position is as shown in  FIG. 6  (a counter-clockwise turn). Thus, to arm door alarm  100 , the alarm would be powered on, and the alarm installed and oriented in the position of  FIG. 5 . Mode selector button  139 - 1  would then be pressed, causing control unit  134  to store the states of tilt switches  130 - 1 ,  130 - 2 , namely, both ON, as indicative of the locked position. Pressing of mode selector button  139 - 1  indicates to control unit  134  that the next orientation in the counter-clockwise direction (i.e. with tilt switch  130 - 1  OFF and tilt switch  130 - 2  ON) is indicative of unlocking and also causes control unit  134  to store the states of the switches in that orientation as being indicative of the unlocked position. 
         [0058]    Once armed, control unit  134  continuously monitors for signals received from tilt switches  130 - 1 ,  130 - 2 . If thumb turn  104  and housing  102  are rotated counter-clockwise from the position shown in  FIG. 5  to the unlocked position of  FIG. 6 , tilt switch  130 - 1  will turn OFF, and tilt switch  130 - 2  will remain ON, indicating to control system  134  that door lock  106  is unlocked. 
         [0059]    When control unit  134  determines that thumb turn  104  is in its unlocked position, counting firmware in control unit  134  increments a count of the number of times door lock  106  has been unlocked. The count is maintained until door lock  100  is reset. In an embodiment, the count may be reset when door lock  100  is powered off using power switch  138 . In another embodiment, the count may be reset when battery  128  is removed from holder  126 . The count may also be reset when it exceeds a predetermined value. 
         [0060]    When the control unit  134  senses the door is unlocked, the, control unit  134  activates speaker  132  and LED  136 . Speaker  132  may emit an alarm signal, such as a loud constant tone, siren, or recorded message and LED  136  may be illuminated. 
         [0061]    The alarm signal generated by speaker  132  and illumination of LED  136  may alert the user of door alarm  100  or other nearby persons of tampering or unauthorized unlocking of door lock  106 . Moreover, if the alarm signal is caused by an intruder unlocking door lock  106 , the loud alarm signal may draw attention and deter the intruder from passing through door  108 . If the door is unlocked by the user, the alarm signal and illuminated LED may provide a reminder to the user to re-lock door lock  106 . 
         [0062]    Control unit  134  may also cause transceiver  142  to transmit an alert message. In an embodiment, the alert message may be a message sent over a cellular network. For example, the alert message may be an SMS message sent to the cellular phone of the owner of door alarm  100 , warning that door  108  has been unlocked. Thus, the user may be alerted by a message sent to a cellular phone, of possible intrusion or tampering with door lock  106  when not in close proximity to door alarm  100 . In other embodiments, transceiver  142  may transmit a message to a dedicated receiver which may be portable and carried by the user of door alarm  100 . In still other embodiments, transceiver  142  may transmit a message to a central monitoring station. 
         [0063]    After door alarm  100  is triggered, that is, after control unit  134  senses that the door is unlocked, control unit  134  continues to activate speaker  132 , even if door alarm  100  is returned to the locked position. Control unit  134  may be caused to deactivate speaker  132  by actuating mode selector buttons  139 - 1 ,  139 - 2  in a predetermined disarming sequence. The disarming sequence may be pre-set in the firmware of control unit  134 , or may be manually set by invoking a programming mode of control unit  134  (such as by actuating mode selector buttons  139 - 1 ,  139 - 2  in a sequence) and then entering a desired disarming sequence. 
         [0064]    Control unit  134  may also be programmed to deactivate speaker  132  when a predetermined time has elapsed after activation. 
         [0065]    The operation of speaker  132 , LED  136  and transceiver  142  may also be controlled to indicate to the user the number of times that thumb turn  104  has been moved to its unlocked position. This may inform the user of tampering or unauthorized access, even if the user does not hear the alarm signal, see the illuminated LED  136  or receive a message from transceiver  142  when such tampering or unauthorized access occurs. 
         [0066]    Thus, when thumb turn  104  is in its locked position such that the alarm is not in alarm mode, speaker  132  and LED  136  could be operated in intermittent or oscillating patterns indicative of the unlock count. Thus, one or both of speaker  132  and LED  136  may be operated in a series of short pulses equal to the unlock count. For example, it may be that when the thumb turn  104  is in the locked position, the control unit  134  may control LED  136  to blink twice at periodic intervals to indicate the door has been unlocked twice since the last reset. 
         [0067]    Conveniently, this may enable a user to determine if tampering or unauthorized unlocking of lock  106  has occurred, even if the user does not hear or receive an alarm signal. If lock  106  is expected to be unlocked a certain number of times, the lock count may advise the user of any locking over and above that number. For instance, if door alarm  100  is used on a hotel room lock, a user may expect the lock to be opened once per day for housekeeping. If speaker  132  or LED  136  indicate that the lock has been opened more than once, a user will know that at least one unlocking was unauthorized or unexpected. 
         [0068]    In other embodiments, control unit  134  may activate speaker  132  when door alarm  100  is moved to any orientation other than the locked orientation. In one such embodiment, mode selector buttons  139 - 1 ,  139 - 2  may be replaced with a single button which, when pressed to arm door alarm  100 , causes firmware of control unit  134  to store the states of tilt switches  130 - 1 ,  130 - 2  and thereafter continually monitor the states of tilt switches  130 - 1 ,  130 - 2 . As will be apparent, any change in state of either of tilt switches  130 - 1 ,  130 - 2  indicates a change in orientation of door alarm  100  and control unit  134  may therefore activate speaker  132  whenever either one of tilt switches  130 - 1 ,  130 - 2  changes from its respective stored state. 
         [0069]    Though the above-described example relates to a thumb turn  104  which is in a horizontal orientation when locked and which rotates counter-clockwise to a vertical orientation when unlocked, those of ordinary skill will appreciate that door alarm  100  could also be used with a thumb turn which is oriented vertically when locked and/or with a thumb turn with rotates clockwise to unlock. 
         [0070]    Moreover, door alarm  100  may be used with thumb turns which are oriented obliquely in the locked and unlocked positions and which rotate through approximately 90 degrees to transition between locked and unlocked states. In such embodiments, door alarm  100  would be installed on the thumb turn and armed with the thumb turn in the locked position, and mode selector buttons  139 - 1 ,  139 - 2  would be used to select the appropriate direction in which the thumb turn rotates to unlock. As will be appreciated, the range of oblique angles in which door alarm  100  will function may be limited by the minimum operational orientations of tilt switches  130 - 1 ,  130 - 2 . In some embodiments, tilt switches  130 - 1 ,  130 - 2  may have a minimum operational angle of 15 degrees. That is, tilt switches  130 - 1 ,  130 - 2  may change states only if inclined by 15 degrees or more from the horizontal. In such embodiments, door alarm  100  may be used in oblique orientations such that, in both the locked and unlocked states, tilt switches are inclined by at least 15 degrees from horizontal. 
         [0071]    Conveniently, door alarm  100  may be easily installed on substantially any rotary grip member (e.g. thumb turn or handle) of any door. Installation may be permanent or temporary, as door alarm  100  may be removed by cutting straps  112 . Moreover, anchor posts  124  and straps  112  allow door alarm  100  to be installed on a wide range of locks, provided the handle is small enough to be received in housing  102  and large enough to be snugly engaged between straps  112  and anchor posts  124 . Anchor posts  124  may be resiliently deformable so that they may deflect slightly to accommodate a wider range of shapes and sizes of door grips. Door alarm  100  may therefore be used as a portable alarm. For example, lock alarm may be used as a temporary, portable alarm on the door lock of a hotel room. 
         [0072]    As described above, door alarm  100  is installed on a thumb turn of a door lock and provides an alarm when the lock is opened (unlocked). However, in other embodiments, door alarm  100  may be installed on other types of rotary hardware of doors. For example, door alarm  100  may be installed on a door handle or door knob and may detect whether the position of the handle or knob is consistent with the door&#39;s latch being open or closed. Accordingly, a user may be provided with an alarm indicating that a door has been opened and counting the number of times the door has been opened, regardless of whether the door itself is equipped with a lock. 
         [0073]    As described above, tilt switches  130 - 1 ,  130 - 2  are oriented at approximately a 45 degree angle to the vertical and approximately a 90 degree angle to one another. In this orientation, tilt switches are effective for detecting movement of thumb turn  104  between horizontal and vertical positions. In other embodiments, tilt switches may be arranged in different orientations so that they switch at different orientations of the housing. The arrangement of tilt switches may be based on the range of motion of the handle to which an alarm is installed. For example, if a thumb turn rotates through more or less than 90 degrees during opening/unlocking, the tilt switches may be re-oriented appropriately so they are OFF in one of the open or closed position and ON in the other of the open or closed position. In addition, more or fewer than two tilt switches may be used in any number of unique orientations so that the combined state of the tilt switches indicates whether the thumb turn is in an open or closed position. 
         [0074]      FIGS. 8-9  depict a door alarm  100 ′ with three tilt switches  130 - 1 ,  130 - 2  and  130 - 3 . Like parts of door alarm  100 ′ to those of door alarm  100  have been designated with like reference numerals. Third tilt switch  130 - 3  is oriented approximately at a 45 degree angle with each of tilt switches  130 - 1 ,  130 - 2 . Since tilt switches  130 - 1 ,  130 - 2  and  130 - 3  are oriented at different angles, each one will change between its respective ON (closed) and OFF (open) states at a different angular position of door alarm  100 ′. Specifically, since tilt switches  130 - 1 ,  130 - 2 ,  130 - 3  are oriented at approximately 45 degree angles to one another, one of tilt switches  130 - 1 ,  130 - 2  and  130 - 3  will change its ON or OFF state with each rotation of door alarm  100 ′ through approximately 45 degrees. Thus, control unit  134  of door alarm  100 ′ may be capable of detecting up to eight different orientations of door alarm  100 ′, separated by approximately 45 degree angles and door alarm  100 ′ may therefore be suitable for use with a thumb turn that only rotates through 45 degrees to open. In other embodiments, more tilt switches may be added at different angular orientations to enable defection of a greater number of discrete angular orientations of a door alarm, at smaller angular intervals. 
         [0075]    In some embodiments, straps  112  may be adjustable other than by forming a ratchet mechanism with retainers  118 . For example, straps  112  may be provided with clasps which may be attached to straps  112  after straps  112  are received through retainers  118  to prevent the straps  112  from slipping out of the retainers  118 . The position of such clasps may be adjustable and may define the effective length of straps  112 . Alternatively, straps may be received through retainers  118  and knotted to prevent slipping out of the retainers. 
         [0076]    In some embodiments, straps may have an integrally-formed head at one end.  FIG. 8  illustrates one such embodiment, where like parts to parts of door alarm  100  ( FIG. 1 ) have been given like reference numerals. As illustrated in  FIG. 10 , a door alarm  100 ″ is installed using straps  112 ′ with heads  113 . Door alarm  100 ″ has strap retainers  118 ′ which differ from strap retainers  118 . Each head  113  is adapted to receive the opposite end  117 ′ of the respective strap  112 ′ and has an internal pawl indicated generally at  111 ′ which forms a ratchet mechanism with teeth  119 ′ on the other end  117 ′ of the respective strap  112 ′. Straps  112 ′ are received in strap retainers  118 ′. Strap retainers  118 ′ are eyelets with central apertures sized so that a free end of a strap  112 ′ can be passed therethrough. To install door alarm  100 ″ to a thumb turn or other rotary grip member of a door, the alarm is positioned over the rotary grip member, and then each of straps  112 ′ is installed by threading a free end through a first strap retainer  118 ′, then around the rotary grip member, around housing  102  and into head  113 . The strap is then tightened by pulling its end through head  113 . The retainers  118 ′, in combination with the head  113 , hold the strap  112 ′ in place. 
         [0077]    In some embodiments, straps may be elasticized loops.  FIGS. 11-12  illustrate one such embodiment, where like parts to parts of door alarm  100  have been given like reference numerals. As illustrated in  FIGS. 11-12 , a door alarm  100 ′″ is installed by looping bands  112 ″ around thumb turn  104  and strap retainers  118 ″. Strap retainers  118 ″ are formed as hooks, with notches  140  opening away from thumb turn  104  to receive and securely hold bands  112 ″. 
         [0078]    In some embodiments, posts  124  may be replaced with walls defining a notch into which thumb turn  104  may be received. For example,  FIG. 13  depicts a door alarm  1000 , identical to door alarm  100 , except that anchor posts  124  have been replaced with anchor walls  124 ′ which extend from the outer walls of housing  102  and from internal wall  122  to define a rearward-facing notch to receive thumb turn  104 . Posts  124  or walls  124 ′ may be constructed of any material and attached to housing  102  in any manner that provides sufficient rigidity to securely brace against thumb turn  104 . As will be appreciated, walls  124 ′ may tend to be more rigid than posts  124  of the same material and attached in the same manner. 
         [0079]    In some embodiments, door alarms may be formed integrally with a rotary hardware of a door, so that the grip of the rotary hardware forms the housing of the alarm. For example,  FIGS. 14-15  depict one such door alarm  2000 . Many components of door alarm  2000  are identical to those of door alarm  100  and are indicated with like numerals. For example, door alarm  2000  comprises a control unit  134  connected to switches  130 - 1 ,  130 - 2 , mode selectors  139 - 1 ,  139 - 2 , transceiver  142 , LED  136  and speaker  132 . Door alarm  2000  further comprises a battery  128  in a battery holder  126 , accessible through a door  215  in housing  202 . A power switch  216  ( FIG. 14 ) is positioned at the rear of housing  202 . 
         [0080]    Door alarm  2000  acts as the thumb turn of a door lock  201 . Housing  202  of door alarm  2000  has a back plate  203  removably attached to transverse wall  122 , for example, using clips (not shown). A shaft  204  extends from back plate  203  and is retained on door  208  with a plate  206 . Shaft  204  may be fixed to back plate  203  or formed integrally with back plate  203 . Shaft  204  is held in door lock  201  by a plate  206 , a collar  210  positioned on shaft  204  outside the door  208  and a lock washer  212  positioned on shaft  204  in the interior of door  208 . Shaft  204  receives a lock shaft  214  which is connected to a deadbolt (not shown) and rotates to actuate the lock. Lock  201  may be operated by turning housing  202 . That is, the deadbolt may be extended when housing  202  is turned to a locked position and retracted when housing  202  is turned to an unlocked position. 
         [0081]    Door alarm  2000  may be operated in substantially the same manner as door alarm  100 . That is, door alarm  2000  may be armed, and the unlocked orientation selected, in substantially the same manner. Control unit  134  then operates as described above in connection with  FIGS. 5-7 . 
         [0082]    Door alarm  2000  may be provided as part of a custom lock  201 . Alternatively, housing  202  and its internal components may be provided along with shaft  204  for retrofitting to an existing lock. For example, plate  206  of a lock may be removed and shaft  204  may be mounted to lock shaft  214  of an existing lock. Shaft  204  may therefore be configured to be mountable to multiple possible types of lock shaft  214  so as to be compatible with multiple kinds (e.g. brands) of locks. 
         [0083]    In some embodiments, shaft  204  may be formed integrally with or attached directly to transverse wall  122  of housing  202 . 
         [0084]    As depicted above in  FIGS. 1-4 , anchor posts  124  of door alarm  100  are connected directly to transverse wall  122  of housing  102 . In some other embodiments, anchor posts may be attached using a removable back plate. Moreover, as depicted in  FIGS. 1-4 , strap retainers are formed on the walls of housing  102 . In other embodiments, strap retainers may be formed on the anchor posts. 
         [0085]    For example,  FIGS. 16-18  depict a door alarm  3000  with a back plate  303  removably attached to a wall  305  of a housing  302  for example using clips (not shown). Anchor posts  324  extend from back plate  303  and define a notch for receiving thumb turn  104 . Anchor posts may be attached to back plate  303  or formed integrally with back plate  303  and may be formed, for example, from metal, plastic or wood. Anchor posts  324  may be coated with a soft or tacky material such as rubber, silicone or the like, to promote frictional engagement with thumb turn  104 . 
         [0086]    Strap retainers  318  may be formed on anchor posts  324 . Strap retainers  318  may be substantially identical to strap retainers  118  ( FIGS. 1-4 ), and are configured to hold straps  112 , for example, by an internal pawl engaging teeth  119  on straps  112  to define a ratchet mechanism. 
         [0087]    Switches  130  are mounted to circuit board  123  using through-hole mounting. In some embodiments, door alarms may be constructed using tilt switches attached to circuit board  123  using a surface mount technique. As depicted in  FIGS. 19-21 , door alarm  3000  has surface mount tilt switches  330 - 1 ,  330 - 2 ,  330 - 3  (individually and collectively, surface mount tilt switches  330 ). Surface mount tilt switches  330  may be oriented parallel to circuit board  123 . That is, in the orientation of door alarm  3000  depicted in  FIG. 19 , surface mount tilt switches may be oriented in a horizontal plane. Surface mount tilt switches  330  are configured to function like tilt switches  130 . That is, when gravity pulls on a switch in the direction indicated by arrow O, the switch is opened (turned off). When gravity pulls in the direction indicated by arrow C, the switch is closed (turned on). Surface mount tilt switches, for example, may each have an internal ramp so that an internal movable element  331  is pulled by gravity and moved in the indicated directions. Surface mount tilt switches  330  may for example be model SQ-SEN-645β switches sold by SignalQuest LLC. As is the case with tilt switches  130 , surface mount tilt switches  330  are oriented at different angles so that they each turn on and off at different orientations of door alarm  3000 , and thus, each combined state of surface mount tilt switches  330  is associated with a particular range of orientations. Surface mount tilt switches  330 - 1 ,  330 - 2  are configured so that their opening directions are 90 degrees from one another, and surface mount tilt switch  330 - 3  is oriented so that its opening direction is 45 degrees from the opening directions of surface mount tilt switches  330 - 1 ,  330 - 2 . 
         [0088]    In some embodiments, door alarms may be constructed using a combination of surface mount and through-hole tilt switches. For example, switches  330 - 1  and  330 - 2  in door alarm  3000  may be replaced with through-hole switches like switches  130 - 1 ,  130 - 2 . 
         [0089]    In some embodiments, one or more supercapacitors may be provided to replace or supplement battery  128 . Configurations including supercapacitors may be well suited for alarms with annunciators that draw relatively high current when activated. An annunciator may be configured to initially draw from a supercapacitor when first activated, which may mitigate sharp current peaks on initial activation of the annunciator. Such a configuration may increase battery life relative to configurations in which a high-current annunciator is powered by a battery alone. 
         [0090]    In some embodiments, door alarms as described herein may comprise additional sensors interconnected with control unit  134 . For example, control unit  134  may be interconnected with a temperature sensor, and may be configured to activate speaker  132  or send a message using transceiver  142  when the temperature sensor measures a temperature above or below a certain threshold. 
         [0091]    As depicted, control unit  134  is a digital controller, which receives as inputs one or more signals indicating the states of tilt switches  130 - 1 ,  130 - 2  and which is equipped with control logic to operate the interconnected components as described above. However, in other embodiments, the door alarm may be controlled using analog circuitry. 
         [0092]    Other modifications will be apparent to those skilled in the art and the invention is therefore defined in the claims.