Radio Transmitting Alarm System

Abstract

A radio transmitting alarm system where each signal actuating device includes a radio transmitter of short range and determined frequency and a self-contained power supply. The switch actuation of the transmitter may include a plunger-type switch, a level-indicating switch using mercury or a heat-responsive switch. The receiving station, as well as having a radio receiver tuned to the same frequency as the transmitter, may have a light, bell or a tape-actuated signal which is sent to a central monitoring station.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of art to which this invention pertains is found in Communications, Electrical and in particular to the subclass wherein the "signal is automatically responsive to a particular condition."

2. Description of the Prior Art

Alarm systems are, in general, well known and include many variations which provide specific functions. Many of these known systems require wire means for conducting the signals from the signal source to the signal receiving or distributing center. Some alarm systems are known wherein a radio transmission and receiving apparatus is made a part of the system. In those known radio alarm systems, the physical size of the transmitting device and the means for powering the transmitting device are principal problems for using such transmitting systems.

Alarm systems which provide for burglar detection, fire or smoke detection and for swimming pool monitoring are both necessary and desirable. These alarm systems may be individual or collective in nature but ease of installation, in testing of the installation and in foolproof operation of the systems have been large and sometimes insurmountable problems.

SUMMARY OF THE INVENTION

The radio transmitting alarm system of this invention provides for a signal originating device which is preferably a self-contained or self-sufficient radio transmitting unit of relatively small size. As a swimming pool monitor, the signal actuation may be in a float tethered in the pool or as a rope or cable actuated signal originating device. As a burglar alarm, the signal actuation and originating device is contained in a tubular member which is mounted in a door, a door stile or in a windowsill. As a signal actuation for a heat-responsive fire alarm, the transmitting device is preferably a tubular member mountable in a hole in a ceiling or wall.

The alarm receiving member or station of this system is adapted to receive the transmitted signal and in response thereto to actuate a bell, siren, light and/or a tape-actuated signal which is relayed to another central monitoring station such as a police or fire station.

As a swimming pool alarm, the radio transmitting unit is exemplified in two embodiments of this invention. One embodiment includes a self-sufficient transmitter and switch in a float adapted to be buoyed on the surface of the water within the swimming pool. The float is tethered by means of a cable or the like to a weight or anchor which is adapted to rest upon the bottom of the pool. This float is hollow, of course, and carries a small radio transmitter which is powered by a battery or other electromotive force self-contained within the float. A fluid switch such as mercury is designed to regulate the current flow from the battery to the transmitter. This mercury switch is responsive to the tipping of the float to a determined angle.

In one embodiment this mercury switch is made adjustably responsive so as to make the switch in the float responsive to greater or lesser waves or splashes greater than the normal average of the waves produced in the pool. In yet another embodiment of the swimming pool alarm, the switch includes two opposed metal members, one of which is cup shaped, and is disposed to carry an electrical current-conducting metal ball, the other member is a circular disk movable towards or away from the circular cup so as to increase or decrease the distance between the opposed metal members. The distance between the members is selectively adjustable so as to limit the amount of tilt of the float required to cause switch to be closed and the transmitter to be actuated.

In yet another embodiment of this swimming pool alarm, a cable or rope is attached to posts disposed in fixed array around the periphery of the pool. Any person, animal or other object falling into the pool engages the cable or rope and causes it to be pulled or deflected to actuate a switch and a resulting radio transmitted signal.

In yet other embodiments of the radio transmitting alarm system there are shown burglar and fire alarms in which a small tubular member encloses the transmitter and battery of the signaling device and one end retains a switch means to activate the transmitter. The switches disclosed include a sliding switch, a reed switch, and a heat-responsive switch which is a spring-actuated switch released in response to a determined amount of heat.

Among the many advantages of the radio alarm system provided by this invention is that the transmitter is of the instant-on type. Such a system permits the batteries used to power the transmitter to remain in a deactivated condition until the switch is closed thereby causing an electric current to flow to the transmitter and a signal to be sent. This design permits the use of very small batteries resulting in a very long life for these same batteries. The transmitter, in the several embodiments of this alarm system, is maintained in a non-transmitting condition during its times of nonuse so that the life of the battery is not unduly shortened.

The receiving station of this alarm system is preferably key controlled and includes a test signal circuit whereby the system may be checked as to whether the receiving circuit is in a proper receiving condition, this checking being done without the actuation of the various signal devices. The key switch also insures that the device is shut off or is in an operating condition and remains in the desired operating condition as determined by the operator.

It is an object of this invention to provide a radio transmitting alarm system in which the transmitter signal device is desirably rendered inoperative during the times of nonuse and in which the receiving station is caused to be actuated only during the times of desired surveillance.

It is a further object of this invention to provide an alarm system wherein a mercury switch having its contacting means in an inert atmosphere is made adjustably responsive to the tilting movement of the switch.

INTENT OF THE DISCLOSURE

Although the following disclosure offered for public dissemination is detailed to insure adequacy and aid in understanding of the invention, this is not intended to prejudice that purpose of a patent which is to cover each new inventive concept therein no matter how it may later be disguised by variations in form or additions of further improvements. The claims at the end hereof are intended as the chief aid toward this purpose, as it is these that meet the requirement of pointing out the parts, improvements or combinations in which the inventive concepts are found.

There has been chosen a specific embodiment of a radio transmitting alarm system and modifications to switching systems as adopted for use therewith. This specific embodiment and the alternate switch constructions used therewith have been chosen for the purposes of illustration and description as shown in the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents a partly diagrammatic view showing a typical installation of a radio transmitting alarm detection system of this invention;

FIG. 2 represents in an enlarged view a typically housed receiving station of this alarm system, the view having a portion of the housing cover broken away to show a tape-controlled signal transmitting device mounted within the housing;

FIG. 3 represents a diagrammatic representation of the disposition of the several transmitting signal alarm members and a receiving station disposed to receive said transmitted signals, the combination providing an alarm system for the protection of persons and property;

FIG. 4 represents a preferred swimming pool alarm signal transmitting device as carried within a tethered float member;

FIG. 5 represents a signal receiving housing and a switch control for the receiving station therewith;

FIG. 6 represents a door-retained signal transmitting device as mounted within a door;

FIG. 7 represents in a substantially full size scale a partly sectional view of the door-retained signal transmitting device of FIG. 6;

FIG. 8 represents a reed switch as disposed in an open condition;

FIG. 9 represents the reed switch of FIG. 8 in a closed condition;

FIG. 10 represents the preferred arrangement of a smoke or fire alarm transmitting device adapted to provide a heat-detecting radio transmitting alarm;

FIG. 11 represents a cross-sectional view of a pool float housing and showing a shock mounting means for retaining the switch and transmitting system therein;

FIG. 12 represents an alternate embodiment of a mercury switch system for use in the swimming pool float and transmitting system of FIG. 4;

FIG. 13 represents yet another alternate embodiment of a switch system in which mercury is used, this switch particularly disposed for use in the swimming pool float and transmitting system of FIG. 4;

FIG. 14 represents a modified embodiment of the mercury switch of FIG. 13, this modified switch also preferably for use in the swimming pool float and transmitting system of FIG. 4;

FIG. 15 represents the mercury switch of FIG. 14, but turned to an inactivated or off condition;

FIG. 16 represents an isometric schematic view of a portion of a swimming pool as provided with a rope signal device, and

FIG. 17 represents a view of a signal support member of the rope signal device of FIG. 16.

In the following description and in the claim various details will be identified by specific names for convenience. These names, however, are intended to be generic in their application. Corresponding reference characters refer to like members throughout the several figures of the drawings.

The drawings accompanying, and forming part of, this specification disclose certain details of construction for the purpose of explanation of the broader aspects of the invention, but it should be understood that structural details may be modified in various respects and that the invention may be incorporated in other structural forms than shown.

DESCRIPTION OF THE ALARM SYSTEM OF FIGS. 1 AND 2

Referring now in particular to FIG. 1, there is shown a building 20 upon which is mounted a housing 21 in which is contained a signal receiving apparatus to be more fully described hereinafter. A determined distance from this building there is shown a swimming pool 22 containing a supply of water 23, in and on this water a float alarm 24 is buoyed by the water and by means of a tether 25 connected to a weight or anchor 26 is maintained in a determined position in the pool. Within the float 24 there is provided an alarm signal transmitting device and a switch means for actuating this device in response to a splash or wave. The construction of the float and signal device is described in detail hereinafter.

Referring now in particular to FIG. 2, there is shown the housing 21 for the signal receiving system. This housing includes a case 28 which may receive a supply of electric current through a conduit 29 and also return an actuated signal through a feed conduit 30 to the interior of the house. This signal may be fed to a telephone line or other monitoring device or service. It is to be noted that the case 28 is contemplated as containing a bell, siren or horn (not shown), but whose sound may emerge through a grid 31. A flashing signal light 32 mounted on the cover of case 28 may also be actuated upon the receipt of a radio transmitted signal. A tape deck 33 is mounted in the case 28 and may be actuated to feed a signal to a telephone line or the like. Such signals may be sent to the police headquarters or to other monitoring stations to inform those guardians of the property or others to be advised.

Referring next to FIG. 3, the receiving station housing 21 is represented in the upper left-hand portion of the phantom parameter of the system. The receiving station includes the tape deck 33, the light 32 and a bell 34 which is mounted behind the grid 31. A radio receiver 35 having an antenna 36 is adapted to receive signals from any of the transmitting devices and upon the receipt of these signals, to cause a signaling relay to close. This actuation causes the light 32 to flash, the bell 34 to ring and the tape deck 33 to start transmitting its signal over the telephone wire to police headquarters, to fire department, or to a burglar protection monitoring system or to other monitoring services. Signals to actuate the radio receiver 35 may be sent from the pool alarm 24 as shown in the lower right-hand portion of FIG. 3, and/or may be sent from a radio transmitting signal device 37 which may be actuated by the moving of a sash portion of a window 38.

A signal transmitting device 39 is connected to a heat-detecting head 40 which includes a switch which is actuated in response to predetermined conditions to cause a signal to be sent to the radio receiver 35. This signal may be actuated in response to the overheating of a room. A door-activated switch-transmitter 41 is adapted also to send a radio signal to the radio receiver 35. A pneumatic actuated switch in a floor mat placed in front of a door or on a step is adapted to actuate a transmitter 42. Another transmitter signaling device 43 is also indicated as mounted within the door 44 itself.

Referring now in particular to FIG. 5, the receiver housing 21 preferably contains a power on lamp 45, as shown in this particular embodiment. The power for the receiver is supplied by means of a flexible cord 46. The antenna 36 extends upwardly from the top of the housing and from the bottom of this housing, a control cable 48 extends to a switch box 49 having a key switch 50 mounted therein. The cover plate of the box also carries a pair of signal lamps 51 and 52. In the use of the switch box 49, it is contemplated that a key 53 is carried to the switch box and is removably inserted in the lock 50 whereupon the key is turned to a first on position, a test is made to actuate a checking signal indicating to the key operator that the signal apparatus is in signal receiving condition. This check is made without causing an actuation of the light 32, bell 34 or tape deck 33. The indication of a satisfactory check is shown by the turning on of the test lamp 52. If the pool alarm 24 has first been thrown in the water the float may be still bobbing as the system is turned on. As the pool alarm would then send signals, the test position of the switch would be maintained until all signals are stopped and a steady illumination is maintained at signal light 52. After the apparatus has been checked for satisfactory signal receiving condition, the switch is then turned to an operating condition whereupon light 51 is illuminated showing the receiving station is in operation. The key 53 is then removed from the lock, leaving the receiving apparatus in an activated condition so that any signal received from any of the transmitters will cause the light 32 to flash, the bell 34 to ring and any other programming signaling to be actuated.

SWIMMING POOL FLOAT OF FIG. 4

Referring next to the pool alarm device of FIG. 4, there is shown the float alarm 24 which includes a lower housing member 54; an upper housing member 55, and a gasket 56 disposed between the members at the juncture of the housing members so that the float, in its operating condition, is a substantially watertight assembly. It is contemplated that members 54 and 55 are molded of plastic and have relatively thin walls and also, of course, that the float alarm assembly 24 must be able to lightly float upon the water. Within the sealed float housing there is mounted a radio transmitter 57 having a determined signal frequency and range. The transmitter is powered by a battery 58. A tilt-responsive switch means in this float alarm includes a lower cup-shaped member 60 and an upper metal member 62 which is disposed a determined distance above member 60. This upper member is carried by a threaded stud 63 which extends through a threaded collar 64 of rubber or plastic. The threaded collar 64 is attached to or is a part of member 55 and is made sufficiently resilient and engages the threaded portion of the stud 63 sufficiently tight so as to keep water from entering the interior of the float housing. Carried by the lower cup metal member is a ball 65, usually of metal. This ball, if not of conductive metal, is at least constructed so that the surface acts as an electric current conductor. This ball may be of steel having a plated conductive surface such as nickel or copper, or the ball may be made of some other metal having a satisfactory electrical current-carrying characteristic. Such a metal is aluminum.

From the metal cup member 60, a conductor 66 extends to one side of the battery 58 while a conductor 67 extends from the other side of the battery to the radio transmitter 57. From the transmitter, a conductor 68 extends to the stud 63, whereupon as the ball 65 is caused to roll to one side of the cup 60, the ball is brought in way of the upper metal member 62 causing current from the battery to be carried between members 60 and 62 by means of the ball 65 and permitting current to flow from the battery to the transmitter 57. It is to be noted that the transmitter 57 and battery 58 are shown as being suspended from the upper float housing member 55; however, this is merely a matter of selection and an alternate support is described hereinafter.

DOOR SIGNAL ALARM OF FIG. 6

Referring next to FIG. 6, there is seen a door frame 70 on which a door 71 is hingedly supported. The door 71 contains a signal transmitting device 43 to be more fully described in conjunction with FIG. 7.

Referring next to the signal device 43 as seen in FIG. 7, the transmitting device includes a switch 72 carried by housing 73, which housing may be a plastic tube. The switch 72 is a commercially obtainable switch designed to be in an open condition when a plunger member 74 of the switch 72 is at either of two extremes of operation. Such extremes occur for example, when a door 71, as seen in FIG. 6, is completely closed or when the door is completely open. The closing actuation of the switch occurs as the plunger 74 is moved from outer extreme to the inner extreme of movement. This switch is a commercial product, Model No. 46, as produced by the Edwards Company, Inc., of Norwalk, Connecticut. The switch 72, is connected to a battery 75 and by means of a metal sleeve 76 carries current forwardly to a radio transmitter 77. The radio transmitter 77 may be similar to, if not exactly like, the radio transmitter 57 of the float alarm above-described. Preferably this transmitter is a crystal-controlled transmitter having a small antenna 78. The battery 75 and transmitter 77 are retained and enclosed within the housing 73 for protection. The housing 73 may be the housing seen in FIG. 6 wherein a flange portion 79 is retained by means of flat head screws 80 within a hole drilled endwise into the door 71.

As reduced to practice the actual diameter of the housing 73 is about three-quarters of an inch or less and the housing 73 itself is about 5 1/2 inches long. This permits the door transmitter signaling device 43 to be installed in nearly any door and particularly a hollow door. When it is determined that the door is not to be drilled, the device 43 may be installed in a hole provided in the frame of the door. As thus installed, the door is closed against the button end of the plunger 74 and the switch 72 is actuated as above-described.

Referring next to FIGS. 8 and 9 there is shown an alternate plunger-type switch commonly known as a reed switch. This reed switch 82 is retained in a forward plunger housing 83 which is mountable in a signaling device similar to the device shown in FIG. 7. In the switch as seen in FIGS. 8 and 9, there is a plunger 84 which carries a magnet 85, which magnet is brought in way of the reed switch 82 causing the contacts of the switch to be closed (FIG. 9). The actuation of the switch is merely a matter of arranging the magnet 85 to provide a switch which is normally in an open or in a closed condition. When it is desired to have the actuation of the plunger close the switch, as for an example, the stepping on a pneumatic pad or the stepping on a tred of a step, the switch shown in FIGS. 8 and 9 is used. It is also to be realized that the switch 82 may be placed at the forward or left position in the housing 83 whereby with the plunger button 84 in the position of FIG. 8, the switch 82 is in the closed condition and with the plunger in the position of FIG. 9, the switch 82 is in an open condition. The housing 83 and switch of FIGS. 8 and 9 may be placed in housing 73 of the device of FIG. 7 as an alternate to the switch 72 shown therein.

HEAT DETECTING SIGNAL DEVICE OF FIG. 10

Referring next to FIG. 10, there is shown the door transmitter 43 of FIG. 7 modified to have a heat detecting head 86 mounted thereon. This head includes a switch, normally open, and is commercially available as Catalog No. 445 from the Edwards Company, Inc., of Norwalk, Connecticut. The heat detecting signal device of FIG. 10 may be mounted in a hole in a ceiling or wall with the detecting head 86 exposed so as to be responsive to a determined degree of heat. A test switch 86a may be provided so that upon actuation of switch 86a a test signal from the transmitter may be sent to the receiving station. This test may be a periodic standard procedure to insure that each of the heat-detecting apparatus is in satisfactory operating condition.

SWIMMING POOL FLOAT OF FIG. 11

Referring next to FIG. 11, it is to be noted that the swimming pool float 24 has upper housing 55 and lower housing 56 provided with foam plastic members 87 and 88. This foam plastic may be Styrofoam, a product of the Dow Chemical Company. These members 87 and 88 are shown as substantially the same thickness and are disposed to snugly meet about midpoint of the interior of the housing. In each member there are formed mating hollow cutout portions sized to accept and support the radio transmitter, the battery, the switch means, the conductors and any other members of the apparatus within the housing which are necessary for the actuation of the float. In addition to acting as a support and shock absorber for the radio transmitter alarm components, the foam members 87 and 88 tend to stiffen and support the plastic pieces 55 and 56.

ALTERNATE FLOAT ALARM SWITCH OF FIG. 12

Referring next to FIG. 12, the upper cover 55 is shown as providing an alternate switch assembly in which a reservoir member 90 is molded integral with the cover portion 55. The reservoir member has an aperture formed in its bottom, and in this aperture there is mounted a conducting screw 91. The threaded end of the screw extends below the reservoir, and attached thereto is a conductor 92 which extends to one side of the battery. A threaded metal cover member 94 has a recessed inner end so shaped as to provide a metal collar portion at its inner end. This metal member 94 is conductively engaged by means of screw post 95 to which a flexible conductor 96 is attached. The conductor 96 extends from the screw post 95 to the transmitter. Within the hollow portion of the reservoir 90 there is provided a supply of mercury 97. The threaded cover member 94 is adjusted up and down in the reservoir so as to vary the distance between the edge of the collar portion of the metal member 94 and the surface of the mercury. This adjusted distance establishes the determined amount of tilting required to bring the mercury into a current conducting engagement with the member 94.

DESCRIPTION OF THE MERCURY SWITCH OF FIG. 13

Referring next to FIG. 13, there is shown a mercury switch in which a glass envelope 100 is hermetically sealed and encloses a metal conducting ring 101. This ring 101 is supported by means of wires 102 and 103 which are also electrical conductors. Centrally carried in the housing 100 is an insulated wire conductor 105 having an exposed central conducting end 106. Within the envelope a determined amount of mercury 107 is provided. Connected to the glass envelope portion 100 is a depending portion 108 which may also contain a portion of mercury 109. By varying the supply of mercury 109, the level of the mercury 107 within the glass envelope 100 is increased or decreased. This transfer of mercury from portion 108 to envelope 100 is made by tapping the depending portion 108 to cause small portions of the mercury 109 to flow to envelope 100 or small portions of mercury 107 to flow to depending portion 108.

DESCRIPTION OF THE MERCURY SWITCH OF FIGS. 14 AND 15

Referring next to FIGS. 14 and 15, it is to be noted that a hermetically sealed glass envelope 110 similar to the envelope 100 also contains a metal ring 101 which is similarly supported by conductors 102 and 103. Centrally carried in the glass envelope 110 is an insulated conductor 105 which has its exposed inner end 106 extending down into a supply of mercury 112. When the envelope 110 is turned upside down, as in FIG. 15, the mercury 112 occupies a determined space below the ring 101 and the exposed inner end of the conducting end 106 of the conductor 105 is disposed a substantial distance above the level of the mercury, insuring that this mercury switch to be in a nonconductive or off condition.

The switches of FIGS. 13, 14 and 15 are glass enclosed and are hermetically sealed and an inert gas is provided to occupy the space in the envelope not taken by the mercury.

ROPE ACTUATED POOL ALARM

Referring finally to FIGS. 16 and 17, there is shown an alternate swimming pool alarm signal system wherein a rope or cable 120 is carried by a plurality of support posts 122. One of the rope supports is a signal alarm post 123 adapted to retain a transmitter 77 and a power source such as a battery 75. A switch such as the switch 110 of FIG. 14 may be used as a signal control device for the transmitter 77. When such a switch is used, the post 123 is carried by a spring 124 mounted in base 125 so that a pull on rope 120 causes the post 123 to be tilted, causing the mercury switch to be brought to an "on" condition and the transmitter 77 to be actuated.

A tension actuated switch (not shown) may be used in the post 123 instead of a mercury switch 110 and a spring 124. The reed switch 82 of FIGS. 8 and 9, for example, may be adapted to be moved to a closed condition upon the pull of the rope 120. The rope 120, of course, is removable from the pool when the pool is to be placed in authorized use. The rope is disposed so that a small child, animal and the like entering or falling into the pool must displace the normal position of the rope around the pool. The rope 120 may be floated on the surface of the water. When so disposed the rope may be one to two feet from the edge of the pool. As in the above water supported rope, the displacement of the rope from its normal condition causes the switch to be closed to actuate the transmitter.

USE AND OPERATION OF SIGNAL SYSTEM

In the above-described alarm signal system, a signal receiving apparatus which is retained in a housing 21 is turned on and off by a key 53. In an off condition, the receipt of any signals from the signal transmitting systems are ineffective. The signal receiving system is also adapted to be tested for operating effectiveness before turning the system to operating condition.

The alarm signaling devices all include a self-contained instant-on type of transmitter. The power supply is usually a battery carried in a housing which also contains the transmitter. The switch for each signal producing control point is a "normally-off" switch which, in response to the action detection, is closed to cause a radio transmitted signal to be broadcast. The signal from each transmitter is a controlled frequency of the same frequency as the radio receiver.

As a swimming pool monitor the signal device may be carried in a float alarm 24 and be actuated by a wave of a greater than determined intensity or height. A switch such as those shown in FIGS. 4, 12, 13 and 14 are all designed to be responsive to a tilting actuation of the float. All these switches are also designed to be rendered positively inactive when the float is removed from the pool and is turned upside down for storage. In the swimming pool monitor of FIGS. 16 and 17, the rope 120 is a removable member which when removed permits the pool to be freely used at selected times. During the time the pool is to be under monitor surveillance, the rope 120 is mounted on the support posts or may be disposed on or over the water.

As a burglar alarm, the door transmitter device 43 of FIG. 7 is mounted in a door or sill. This device may also be mounted in a windowsill, in a step tread or in any other movable or actuated member whose movement would indicate the presence of an intruder or a trespassing animal or child. As a fire alarm signal device, the heat responsive switch of FIG. 10 is disposed to actuate a transmitter 77 to send a signal to the receiver.

As a surveillance system, the radio transmitting signal system permits an effective and flexible monitoring system to be easily installed. This system requires no wires between signal actuation station and signal receiving station. The system may be activated only during selected periods of time and the system may provide a multiple and variable type of monitoring requiring only one receiving station.

A common frequency is contemplated as being used in all transmitters but it is realized that a plurality of frequencies may be used, if desired. When plural frequencies are used the receiving control station is provided with means to differentiate between the frequencies of signal. For example, the receiver may have a dual frequency detecting means, one frequency disposed to indicate and be actuated in response to the fire detecting monitors, while a second frequency would be used to receive and be actuated by signals sent from a burglar alarm monitor installation. The effective range of radio transmission signals from the various transmitters is contemplated as being limited to a few hundred feet.

Terms such as "up," "down," "bottom," "top," "front," "back," "in," "out," and the like are applicable to the embodiments shown and described in conjunction with the drawings. These terms are merely for the purposes of description and do not necessarily apply to the position in which the radio transmitting alarm system members or units may be constructed or used and protection is sought to the broadest extent the prior art allows.

Claims

What is claimed is:

1. As an article of manufacture for use in a radio transmitting alarm system in the surveillance monitoring of a door or other movable object, a self-contained radio-transmitter unit comprising an elongated tubular housing of relatively small cross-section extent, said housing including mounting flange means at one axial end, whereby in application to a bore open to an edge of the door or other movable object the housing may be inserted in the bore and the flange means secured at the edge plane of the door or other movable object, said housing including a radio-transmitting member having an instant-on transmitter of determined regulated frequency and having a range at least no greater than a few hundred feet, a battery source within said housing for powering said transmitter, a switch which is normally open during the time the transmitter is placed in surveillance condition and which is normally closed when an alarm signal is sent, said switch being connected to control the flow of electrical current from said source to said transmitter, and a mechanically axially displaceable element carried by said housing and positioned for response to be monitored, said element including a resiliently outwardly urged portion projecting outwardly of said housing and beyond the general plane of said flange means and to a limited extent lending the same to cammed actuation upon interference with a door jamb or the like upon movement of the door or other movable object toward or away from the door jamb or the like, said element being disposed to control operation of said switch from open to closed position upon occurrence of said movement.

2. The article of claim 1 in which the switch for controlling the flow of current to the transmitter is a plunger-type switch carried by the tubular housing, the plunger-type switch being in an "off" condition at its two extremes of movement and being brought into an "on" condition when the plunger is moved past a point intermediate these extremes of movement.

3. The article of claim 1 in which the switch for controlling the flow of current to the transmitter is carried by the tubular housing, said switch including a plunger carried in a support means in the housing, a magnet carried by the plunger and movable therewith, a reed switch carried by the housing, the reed switch disposed to be actuated by the magnet as the magnet is moved to a determined position in the housing.

4. The article of claim 1, in which said mechanically displaceable element is guided within said housing for axial displacement between two portions, said switch being disposed to be closed only for positioning of said element between said two positions; whereby, when said article is installed blind in a bore normal to the hinged edge of a door in such adjacency to the door frame that if the door is closed said element is displaced to the inner of said two positions, a closure of said switch will occur for less than full opening of the door, and the switch will reopen for full opening of the door.

5. The article of claim 1 wherein said housing comprises a plastic tube.