PORTABLE SECURITY ALARM AND ALARM SYSTEM
United States Patent 3710371
A portable alarm system including at least one alarm device triggered when displaced from a normal position. A mercury switch triggers a latching type semi-conductor switch, causing electrical current to energize an alarm. Once sounded, the alarm cannot be silenced unless the correct procedure or key method is followed.
US Patent References:
Prowler alarm
Herst et al. - October 1967 - 3345627
Power control circuit
Laishley - June 1965 - 3189759
SELF-CONTAINED CONTACT ALARM DEVICE
Goldfarb et al. - September 1969 - 3465325
Baby guard
Charles - June 1962 - 3041594
System for signalling unauthorized displacement of an article
Eberts - April 1966 - 3247502
Prowler alarm
Herst et al. - October 1967 - 3345627
Power control circuit
Laishley - June 1965 - 3189759
SELF-CONTAINED CONTACT ALARM DEVICE
Goldfarb et al. - September 1969 - 3465325
Baby guard
Charles - June 1962 - 3041594
System for signalling unauthorized displacement of an article
Eberts - April 1966 - 3247502
Inventors:
Whalen, George J. (White Plains, NY)
Graf, Rudolf F. (New Rochelle, NY)
Graf, Rudolf F. (New Rochelle, NY)
Application Number:
05/012344
Publication Date:
01/09/1973
Filing Date:
02/18/1970
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
340/539.100, 340/327, 340/689, 327/483, 327/475, 340/539.260, 340/429, 340/531
International Classes:
G08B13/14; G08B13/14
Field of Search:
340/283,280,276,384E,224,261,327
US Patent References:
Primary Examiner:
Trafton, David L.
Claims:
We claim
1. An alarm system comprising a source of electrical power, alarm means for producing an alarm signal when connected to said source of electrical power, first switch means for providing a gating pulse, a latching gate, said first switch means being connected to said latching gate, said latching gate being responsive to said gating pulse for connecting said alarm means to said source of electrical power, and second switching means different from said first switch means for disconnecting said alarm means from said source of electrical power, said latching gate including a silicon controlled rectifier, said first switch means including a mercury switch, said second switch means including shunt means connected across said latching gate for diverting electrical power away from said latching gate.
2. The alarm device set forth in claim 1, wherein said second switch means is provided with a high gain current amplifier, a pair of contact means for causing current to flow through said high gain current amplifier when said contact means are activated, said high gain current amplifier shunting said latching gate diverting electrical power from said latching gate when said pair of contact means are activated and further disconnecting said alarm means from said source of electrical power when said contact means are deactivated.
3. The alarm device set forth in claim 2, including a housing having said alarm means, said source of electrical power, said first and second switch means, and said latching gate being located therein, said latching gate connecting said source of electrical power to said alarm means when said housing is displaced from a normal position.
4. The alarm device set forth in claim 3, wherein said first switch means includes a mercury switch being gravity responsive and connecting said source of electrical power to said alarm means when said housing is displaced from said normal position, said housing being provided with a bottom capable of adhering to non-level surfaces.
1. An alarm system comprising a source of electrical power, alarm means for producing an alarm signal when connected to said source of electrical power, first switch means for providing a gating pulse, a latching gate, said first switch means being connected to said latching gate, said latching gate being responsive to said gating pulse for connecting said alarm means to said source of electrical power, and second switching means different from said first switch means for disconnecting said alarm means from said source of electrical power, said latching gate including a silicon controlled rectifier, said first switch means including a mercury switch, said second switch means including shunt means connected across said latching gate for diverting electrical power away from said latching gate.
2. The alarm device set forth in claim 1, wherein said second switch means is provided with a high gain current amplifier, a pair of contact means for causing current to flow through said high gain current amplifier when said contact means are activated, said high gain current amplifier shunting said latching gate diverting electrical power from said latching gate when said pair of contact means are activated and further disconnecting said alarm means from said source of electrical power when said contact means are deactivated.
3. The alarm device set forth in claim 2, including a housing having said alarm means, said source of electrical power, said first and second switch means, and said latching gate being located therein, said latching gate connecting said source of electrical power to said alarm means when said housing is displaced from a normal position.
4. The alarm device set forth in claim 3, wherein said first switch means includes a mercury switch being gravity responsive and connecting said source of electrical power to said alarm means when said housing is displaced from said normal position, said housing being provided with a bottom capable of adhering to non-level surfaces.
Description:
Security systems are finding increasing personal use as well as in homes, automobiles, and factories. The systems generally available are frequently expensive, unreliable and complex to set. In addition, once sounded, the alarm signal is easily squelched by an intruder, thus detracting from its effectiveness. In addition, industrial and home alarm systems are, generally, stationary, thus permitting one to study the system to avoid triggering it.
An object of the present invention is to provide an improved security system.
Another object of the present invention is to provide an alarm device which is reliable, sturdy, easy to set, and passive prior to actuation, so that detection by an intruder is made substantially more difficult than with present alarm systems.
Still another object of the present invention is to provide a security alarm system which is difficult to silence after it is sounded.
Yet another object of the present invention is to provide a portable alarm system capable of being easily carried and moved, so as to afford the user the option of changing the setup of the alarm system by readily changing the location of the sensors within the area to be protected.
Still another object of the present invention is to provide an alarm system which is capable of being easily triggered, not only because of its inherent sensitivity, but also because of the "surprise" element resulting from the complete freedom of placement and variability of location made possible by use of sensing means which are not "tied down" by connecting wiring or the like.
A further object of the present invention is to provide an alarm system in which the independent alarm units can be readily camouflaged as ordinary packages, containers, merchandise or the like to further conceal the presence of an alarm system from the unwary intruder.
A still further object of the present invention is to provide an alarm system capable of producing either audible or non-audible signals to be remotely sensed.
Other objects, advantages and features of the present invention will be made more apparent from the following description.
In accordance with the principles of the present invention, these objects are accomplished by providing a security system including at least an alarm device comprising a housing being disposed in a normal position, a source of electrical current, alarm means in the housing for producing an alarm signal when energized, gating means in the housing connected to the alarm means for supplying the electrical current to the alarm means, and first switching means in the housing for controlling the gating means and causing the gating means to supply electrical current to the alarm means producing an alarm signal when the housing is displaced from the normal position.
The alarm device includes a mercury switch, enclosed in the housing, so that when the housing is displaced from its normal position, the mercury switch closes, triggering the gating means to supply electrical current to the alarm. With the housing of the alarm device being provided with a high center of gravity, the device is tipped easily thus triggering the alarm. The device is relatively light in weight and can be carried personally. In addition, its location can be changed frequently, thereby preventing the security system from being avoided. The alarm device can be placed in any desired portal, desk drawer, on counter tops, atop merchandise, on baggage, in vehicles to emit a periodic audible alarm when displaced from its normal position. By placing a plurality of such alarm units in a protected area and providing an audible or a non-audible alarm signal capable of being remotely detected, a relatively fool-proof security alarm system is achieved. Use of an audible local alarm may create panic in an unwary intruder, thereby reducing his probable changes for escape. In some cases, a non-audible local alarm may be deemed proper as the means of actuating a remote central alarm, to assist in capture of intruders while "in the act."
As another principle of the present invention, once the alarm is sounded, it cannot be silenced unless a prescribed key method or procedure is followed. In one embodiment, a "touch" switch silences the alarm only when its contacts are simultaneously touched with moistened finger tips. The contacts are placed on the outer surface of the housing and may easily be hidden from the unwary intruder. Considerable latitude in the use of hidden switching means is envisioned.
FIG. 1 is a side elevation view of one possible configuration of the alarm device of the present invention shown capable of being tipped;
FIG. 2 is an exploded assembly view of the alarm device;
FIG. 3 is a schematic diagram of one embodiment of the alarm circuit of the present invention;
FIG. 4 is a schematic diagram of another embodiment of the alarm circuit of the present invention; and,
FIG. 5 is a block diagram of an alarm system utilizing the alarm device.
The present invention provides a compact, yet sturdy alarm unit, which is capable of being placed on any surface and which when placed in an armed state, will signal its being moved from a normal position. The alarm may be audible or inaudible, as desired, and is relatively light and, therefore, portable. For personal use, it may be placed on an attache case while one is in a telephone booth and will be sounded if the alarm or attache case is moved. For convenience, the alarm is capable of being switched to a disarmed state preventing its being sounded whether or not its position changes. When in this state, the alarm may be jostled without sounding. A security system may be provided with a plurality of such alarm devices to protect a large area.
The alarm unit 10 may be cylindrical in shape and fabricated of a relatively sturdy and durable material to withstand rough use and prevent tampering. Considerable variation is possible in the outward appearance of the alarm unit, to permit its disguise, as an object of merchandise or other object normally found in a store, home or office, which an intruder would not suspect of being an alarm device. The components of the alarm device are placed within the alarm unit and preferably in the upper portion thereof to provide a relatively high center of gravity. Thus, when the device is placed on a level surface, it may readily be tipped when disturbed. The housing 12 of the unit includes a rounded and weighted bottom to be self-righting when disturbed and also usable on non-level surfaces. As another embodiment of the present invention, the central portion of the rounded bottom may be magnetized so that the unit could be placed on a non-level metal surface with some degree of adhesion, but still remaining free to be tipped when disturbed. As still another alternative, a temporary adhesive could also be utilized.
As described above, preferably the components of the alarm device are mounted within the housing 12. The alarm 14 is attached to the top portion of housing 12, and may be a "Sonalert" type (registered trademark of P. R. Mallory & Co., Inc.), which is an acoustical generator producing an audio tone of approximately 70 decibels interrupted at a period of 3 to 5 Hertz. It should be noted that this "Sonalert" would give way to other suitable means of signal generation where a non-audible alarm was desired. Such non-audible alarm signal generators could comprise ultrasonic or radio-frequency oscillators, suitably modulated so as to assure fool-proof detection by a remote central monitor. The components of the alarm device are mounted on and between oppositely disposed mounting plates 16 and 18. The plates are held together by means of threaded screws 20, 22 and 24 which fit through corresponding holes oppositely disposed in support plates 16 and 18. The alarm unit is powered by batteries connected in series to terminals 26 and 28. The batteries preferably are portable and may be rechargeable, if desired. The mounted components shown in FIG. 2 are schematically illustrated in FIG. 4 and will be described with reference to that Figure. After the functional description of this schematic circuit shown in FIG. 4 is completed, the components shown in FIG. 2 will be identified.
FIGS. 3 and 4 present schematic diagrams of an alarm circuit used with the present invention, and in addition, illustrate two different turn off procedures employed to silence the alarm. Electrical power for the alarm is provided by an internal battery 30 with the positive electrode of the battery connected to the positive terminal of the alarm 32. The negative terminal of the alarm is connected to the anode of a silicon controlled rectifier 34. Alarm 32, as described above, is capable of providing periodic bursts of sound at a specific frequency when energized. Silicon controlled rectifier 34 is a bi-stable semi-conductor device which conducts when a triggering pulse is applied to the gate terminal of the device. In effect, the silicon controlled rectifier 34 "latches on". The rectifier will remain conducting until the current through it falls below a pre-determined level. A General Electric type C106Y1 silicon controlled rectifier may be used with the principles of the present invention, although any other latching device would be suitable. The cathode of silicon controlled rectifier 34 is connected through a key operated switch 36 controlled by key 37 to the negative electrode of battery 30. When the silicon controlled rectifier 34 is triggered and conducting, the series path of battery 30, alarm 32, silicon controlled rectifier 34, and key operated switch 36 provides a closed circuit sounding the alarm 32. In its normal state, silicon controlled rectifier 34 is not conducting. The positive electrode of battery 30 is connected to a mercury switch 38 having contacts capable of being electrically connected by means of an electro-conductive blob of mercury 43 moving in response to gravity when the orientation of the switch 38 is altered in relation to the normal rest position. Normally, the contacts 40 and 42 are not so connected; that is, the mercury blob does not simultaneously touch both of the contacts. By placing contact 42 permanently in mercury blob 43 and contact 40 very close to the mercury blob, a slight alteration in the position of the alarm device will cause the mercury blob to close the electrical path between contacts 40 and 42.
The positive electrode of battery 30 is connected to contact 40. Contact 42 is connected through a parallel connection of resistor 44 and capacitor 46 to the gate terminal of silicon controlled rectifier 34. A resistor 50 is connected between the gate terminal and the cathode of the silicon controlled rectifier 34. Resistors 44 and 50 and capacitor 46 provide a wave shaping function for the triggering pulse applied to the gate terminal.
The positional sensor of the alarm is the mercury switch 38 which detects a disturbance of the unit from its normal position. Once the alarm is sounded, the circuit remains active, operating on the internal battery supply 30. In operation, the unit is placed in a predetermined position, so that the mercury blob 42 does not close contacts 40 and 42, and the key operated switch 36 is placed to its arm position. When the mercury switch 38 closes the electrical path between contacts 40 and 42, a trigger pulse is applied to the gate terminal of silicon controlled rectifier 34 triggering it into its conducting state. Once triggered, the rectifier 34 remains "latched" in the conducting state closing the above described path for current flow through the alarm 32. Thus, the alarm sounds and continues in operation until the unit is disarmed or the internal battery is exhausted. By turning, the key operated switch 36 to its disarm position, the current supplied through silicon controlled rectifier device 34 is interrupted, turning off the alarm. It should be noted that the alarm cannot be turned off by positional changes, only by use of a "key" method. By providing a relatively sturdy housing for the device, the sounding of the alarm cannot be interrupted by an intruder, unless he possess the required key method. The"panic property" inherent in a device which cannot be deactivated by a startled intruder, lacking the required knowledge to silence the alarm, is a principal feature of the present invention.
FIG. 4 presents a schematic diagram including the same alarm circuit shown in FIG. 3 and with similar components designated as primed numerals. The operation of the alarm circuit need not be repeated again except to point to differences therein. In FIG. 3, a key operated switch 36 was utilized as a master control for the device. In FIG. 4, a switch 52, preferably not key operated, is placed in the trigger circuit for the silicon controlled rectifier device 34'. Therefore, when switch 52 is in its arm position, silicon controlled rectifier device 34' is capable of being triggered. But, once the alarm has been trigger, should switch 52 be placed in its disarm position, the silicon controlled rectifier will continue to operate because the current supplied to it will not be interrupted by placing switch 52 in its disarm position. To this end, switch 52 is connected between the positive electrode of battery 30' and contact 40'. As above, when switch 52 is placed in its arm position, electrical power is available to trigger silicon controlled device 34' when the mercury switch 38' closes contact 40' and 42'. Therefore, switch 52 must first be placed in the arm position before the silicon controlled rectifier 34' is triggered into its conducting state, sounding alarm 32'.
Rather than using the key operated switch to silence the alarm, a "tough" switch 53 is utilized including a solid-state circuit which is energized when two contacts 62 and 64 are simultaneously touched with moistened finger tips. The touch switch can be completely concealed in the design of the alarm unit so that its presence is undetectable to the uninformed observer. The semi-conductor circuit includes a Darlington type amplifier 54. A Darlington amplifier comprises cascaded transistors providing an extremely high input and extremely low output impedance and having a high current gain. The collector of NPN transistor 56 is connected to the collector of NPN transistor 58. The emitter of transistor 56 is connected to the base of transistor 58, while the base of transistor 56 is connected through a limiting resistor 60 to touch contact 62. The emitter of transistor 58 is connected to the cathode of silicon controlled rectifier 34', while the collectors of transistors 56 and 58 are connected to the anode of rectifier 34'. Contact 64 is connected to contact 40' of the mercury switch 38'. To conserve space, the Darlington amplifier may be a monolithic type integrated circuit of which a General Electric type 2N5306 is typical. Other suitable amplifier/switching devices may be utilized.
Normally, the Darlington amplifier 54 is not active. In order to silence the alarm after it has been triggered, moistened finger tips are applied to the touch contacts 62 and 64. When the touch contacts are so bridged, a minute direct current is applied through the skin resistance to the base of transistor 46. This current is sufficient to cause the Darlington amplifier to conduct, thereby shunting current away from silicon controlled rectifier 34' and sufficiently impeding the current flow through the rectifier causing it to be non-conductive. When the fingers are subsequently removed from contacts 62 and 64, the current flowing through the alarm 32' is interrupted, silencing the alarm. To the unwary intruder, who may attempt to silence the alarm by turning the switch 52 to its disarm position, the continuing sounding of the alarm can only cause panic, thereby being thrown into the desired state of disorientation which will hinder his escape.
A plurality of "touch" switches may be included in the circuit to heighten the complexity of the turn-off function. These switch circuits may be so arranged that coincident operation is necessary. Of they may be so configured that one circuit will negate the function of the other when both are simultaneously activated. The meaning of the switching function would be construed broadly to include such alternatives.
With the alarm circuit shown in FIGS. 3 or 4, the device may be manually carried from place to place without triggering the alarm by placing the switches 36 and 52 to the disarm position, thus preventing current from flowing through alarm devices 32 and 32' and triggering silicon controlled rectifiers 34 and 34' respectively.
The assembly diagram of the device presented in FIG. 2 includes the components shown in FIG. 4. The silicon controlled rectifier 34' is mounted to support plate 18 and resistors 44' and 50' are connected to the silicon controlled rectifier device and are located between support plates 16 and 18. Capacitor 46' is also located between the support plates. Darlington device 54 is attached to support plate 18, while mercury switch 38' is attached between support plates 16 and 18. Resistor 60 is also connected between the support plates while master switch 52 is connected to the housing 12 of the alarm device. While the arrangement of the components shown in FIG. 2 enables the device to be assembled and housed completely within housing 12, other physical arrangements for the components may be devised by those of ordinary skill in the art.
While the above described alarm device 10 can be used as a security alarm protecting against unwary intruders, it may also be used as a fire detection alarm. To achieve this, a thermally actuated bi-metallic, normally open, switch paralleling the mercury switch may be included. Thus, when a substantial heat rise of the ambient air occurs, the bi-metallic switch contacts close, triggering the alarm in the same manner as the above described mercury switch.
While a single alarm unit has been described above, it should be noted that a number of similar independent units may be placed at strategic locations, each being capable of being altered in position, creating an alarm system providing security for a relatively large area. The units designated 70, 72 and 74, when triggered, may produce an audible or inaudible alarm. When an inaudible alarm is produced, suitable transducers 76 and 78 tuned to pick up the inaudible alarm signal, activate a central monitoring system 80 which in turn activates a main alarm 82 or any of a plurality of remote alarms 84. Each transducer is tuned to an alarm frequency of, for instance, 2,800 Hertz while transducers 76 and 78 reject other frequencies. Suitable means for discriminating between the true alarm signal and a random, unwanted signal of like frequency could be provided in the central monitor, wherein coincident reception of the desired frequency signal and an accompanying pulse modulation or audio modulating frequency would be required before the central monitor would activate the main alarm system. This would prevent "nuisance" alarms. A modulated ultrasonic or radio frequency transmission system may be used between the alarm devices, transducers 76 and 78 and central monitor system 80. The central monitor may activate such remote and local alarms as telephone dialers, alarm bells, lights or other similar warning devices. In the case of an audible system, suitable transmission techniques are employed to prevent the central monitor from picking up extraneous noise signals, and, to this end, the alarm signal produced by alarm units 70, 72 and 74 may be at a fixed frequency of 2800 Hertz modulated at a 3 to 5 Hertz rate. It is impossible that a similar extraneous noise signal, having these characteristics, will be produced, thus insuring that the central monitor will be responsive only to the actual triggering of an alarm unit. Because the alarm units 70, 72 and 74 are portable, their positions may be changed nightly, thus preventing "casing" of the protected area by even the most skillful burglar. The entirely passive nature of the alarm units, when armed but not activated, also enhances the effectiveness of the system by giving no sign of their presence or location.
It may be seen that the above objects are efficiently accomplished and obtained by the principles of the present invention. Further, the above description merely illustrates the principles of the present invention and should not be construed in a limiting sense. To that end, therefore, the invention should be accorded its full scope of protection to which it is entitled by this patent application.
An object of the present invention is to provide an improved security system.
Another object of the present invention is to provide an alarm device which is reliable, sturdy, easy to set, and passive prior to actuation, so that detection by an intruder is made substantially more difficult than with present alarm systems.
Still another object of the present invention is to provide a security alarm system which is difficult to silence after it is sounded.
Yet another object of the present invention is to provide a portable alarm system capable of being easily carried and moved, so as to afford the user the option of changing the setup of the alarm system by readily changing the location of the sensors within the area to be protected.
Still another object of the present invention is to provide an alarm system which is capable of being easily triggered, not only because of its inherent sensitivity, but also because of the "surprise" element resulting from the complete freedom of placement and variability of location made possible by use of sensing means which are not "tied down" by connecting wiring or the like.
A further object of the present invention is to provide an alarm system in which the independent alarm units can be readily camouflaged as ordinary packages, containers, merchandise or the like to further conceal the presence of an alarm system from the unwary intruder.
A still further object of the present invention is to provide an alarm system capable of producing either audible or non-audible signals to be remotely sensed.
Other objects, advantages and features of the present invention will be made more apparent from the following description.
In accordance with the principles of the present invention, these objects are accomplished by providing a security system including at least an alarm device comprising a housing being disposed in a normal position, a source of electrical current, alarm means in the housing for producing an alarm signal when energized, gating means in the housing connected to the alarm means for supplying the electrical current to the alarm means, and first switching means in the housing for controlling the gating means and causing the gating means to supply electrical current to the alarm means producing an alarm signal when the housing is displaced from the normal position.
The alarm device includes a mercury switch, enclosed in the housing, so that when the housing is displaced from its normal position, the mercury switch closes, triggering the gating means to supply electrical current to the alarm. With the housing of the alarm device being provided with a high center of gravity, the device is tipped easily thus triggering the alarm. The device is relatively light in weight and can be carried personally. In addition, its location can be changed frequently, thereby preventing the security system from being avoided. The alarm device can be placed in any desired portal, desk drawer, on counter tops, atop merchandise, on baggage, in vehicles to emit a periodic audible alarm when displaced from its normal position. By placing a plurality of such alarm units in a protected area and providing an audible or a non-audible alarm signal capable of being remotely detected, a relatively fool-proof security alarm system is achieved. Use of an audible local alarm may create panic in an unwary intruder, thereby reducing his probable changes for escape. In some cases, a non-audible local alarm may be deemed proper as the means of actuating a remote central alarm, to assist in capture of intruders while "in the act."
As another principle of the present invention, once the alarm is sounded, it cannot be silenced unless a prescribed key method or procedure is followed. In one embodiment, a "touch" switch silences the alarm only when its contacts are simultaneously touched with moistened finger tips. The contacts are placed on the outer surface of the housing and may easily be hidden from the unwary intruder. Considerable latitude in the use of hidden switching means is envisioned.
FIG. 1 is a side elevation view of one possible configuration of the alarm device of the present invention shown capable of being tipped;
FIG. 2 is an exploded assembly view of the alarm device;
FIG. 3 is a schematic diagram of one embodiment of the alarm circuit of the present invention;
FIG. 4 is a schematic diagram of another embodiment of the alarm circuit of the present invention; and,
FIG. 5 is a block diagram of an alarm system utilizing the alarm device.
The present invention provides a compact, yet sturdy alarm unit, which is capable of being placed on any surface and which when placed in an armed state, will signal its being moved from a normal position. The alarm may be audible or inaudible, as desired, and is relatively light and, therefore, portable. For personal use, it may be placed on an attache case while one is in a telephone booth and will be sounded if the alarm or attache case is moved. For convenience, the alarm is capable of being switched to a disarmed state preventing its being sounded whether or not its position changes. When in this state, the alarm may be jostled without sounding. A security system may be provided with a plurality of such alarm devices to protect a large area.
The alarm unit 10 may be cylindrical in shape and fabricated of a relatively sturdy and durable material to withstand rough use and prevent tampering. Considerable variation is possible in the outward appearance of the alarm unit, to permit its disguise, as an object of merchandise or other object normally found in a store, home or office, which an intruder would not suspect of being an alarm device. The components of the alarm device are placed within the alarm unit and preferably in the upper portion thereof to provide a relatively high center of gravity. Thus, when the device is placed on a level surface, it may readily be tipped when disturbed. The housing 12 of the unit includes a rounded and weighted bottom to be self-righting when disturbed and also usable on non-level surfaces. As another embodiment of the present invention, the central portion of the rounded bottom may be magnetized so that the unit could be placed on a non-level metal surface with some degree of adhesion, but still remaining free to be tipped when disturbed. As still another alternative, a temporary adhesive could also be utilized.
As described above, preferably the components of the alarm device are mounted within the housing 12. The alarm 14 is attached to the top portion of housing 12, and may be a "Sonalert" type (registered trademark of P. R. Mallory & Co., Inc.), which is an acoustical generator producing an audio tone of approximately 70 decibels interrupted at a period of 3 to 5 Hertz. It should be noted that this "Sonalert" would give way to other suitable means of signal generation where a non-audible alarm was desired. Such non-audible alarm signal generators could comprise ultrasonic or radio-frequency oscillators, suitably modulated so as to assure fool-proof detection by a remote central monitor. The components of the alarm device are mounted on and between oppositely disposed mounting plates 16 and 18. The plates are held together by means of threaded screws 20, 22 and 24 which fit through corresponding holes oppositely disposed in support plates 16 and 18. The alarm unit is powered by batteries connected in series to terminals 26 and 28. The batteries preferably are portable and may be rechargeable, if desired. The mounted components shown in FIG. 2 are schematically illustrated in FIG. 4 and will be described with reference to that Figure. After the functional description of this schematic circuit shown in FIG. 4 is completed, the components shown in FIG. 2 will be identified.
FIGS. 3 and 4 present schematic diagrams of an alarm circuit used with the present invention, and in addition, illustrate two different turn off procedures employed to silence the alarm. Electrical power for the alarm is provided by an internal battery 30 with the positive electrode of the battery connected to the positive terminal of the alarm 32. The negative terminal of the alarm is connected to the anode of a silicon controlled rectifier 34. Alarm 32, as described above, is capable of providing periodic bursts of sound at a specific frequency when energized. Silicon controlled rectifier 34 is a bi-stable semi-conductor device which conducts when a triggering pulse is applied to the gate terminal of the device. In effect, the silicon controlled rectifier 34 "latches on". The rectifier will remain conducting until the current through it falls below a pre-determined level. A General Electric type C106Y1 silicon controlled rectifier may be used with the principles of the present invention, although any other latching device would be suitable. The cathode of silicon controlled rectifier 34 is connected through a key operated switch 36 controlled by key 37 to the negative electrode of battery 30. When the silicon controlled rectifier 34 is triggered and conducting, the series path of battery 30, alarm 32, silicon controlled rectifier 34, and key operated switch 36 provides a closed circuit sounding the alarm 32. In its normal state, silicon controlled rectifier 34 is not conducting. The positive electrode of battery 30 is connected to a mercury switch 38 having contacts capable of being electrically connected by means of an electro-conductive blob of mercury 43 moving in response to gravity when the orientation of the switch 38 is altered in relation to the normal rest position. Normally, the contacts 40 and 42 are not so connected; that is, the mercury blob does not simultaneously touch both of the contacts. By placing contact 42 permanently in mercury blob 43 and contact 40 very close to the mercury blob, a slight alteration in the position of the alarm device will cause the mercury blob to close the electrical path between contacts 40 and 42.
The positive electrode of battery 30 is connected to contact 40. Contact 42 is connected through a parallel connection of resistor 44 and capacitor 46 to the gate terminal of silicon controlled rectifier 34. A resistor 50 is connected between the gate terminal and the cathode of the silicon controlled rectifier 34. Resistors 44 and 50 and capacitor 46 provide a wave shaping function for the triggering pulse applied to the gate terminal.
The positional sensor of the alarm is the mercury switch 38 which detects a disturbance of the unit from its normal position. Once the alarm is sounded, the circuit remains active, operating on the internal battery supply 30. In operation, the unit is placed in a predetermined position, so that the mercury blob 42 does not close contacts 40 and 42, and the key operated switch 36 is placed to its arm position. When the mercury switch 38 closes the electrical path between contacts 40 and 42, a trigger pulse is applied to the gate terminal of silicon controlled rectifier 34 triggering it into its conducting state. Once triggered, the rectifier 34 remains "latched" in the conducting state closing the above described path for current flow through the alarm 32. Thus, the alarm sounds and continues in operation until the unit is disarmed or the internal battery is exhausted. By turning, the key operated switch 36 to its disarm position, the current supplied through silicon controlled rectifier device 34 is interrupted, turning off the alarm. It should be noted that the alarm cannot be turned off by positional changes, only by use of a "key" method. By providing a relatively sturdy housing for the device, the sounding of the alarm cannot be interrupted by an intruder, unless he possess the required key method. The"panic property" inherent in a device which cannot be deactivated by a startled intruder, lacking the required knowledge to silence the alarm, is a principal feature of the present invention.
FIG. 4 presents a schematic diagram including the same alarm circuit shown in FIG. 3 and with similar components designated as primed numerals. The operation of the alarm circuit need not be repeated again except to point to differences therein. In FIG. 3, a key operated switch 36 was utilized as a master control for the device. In FIG. 4, a switch 52, preferably not key operated, is placed in the trigger circuit for the silicon controlled rectifier device 34'. Therefore, when switch 52 is in its arm position, silicon controlled rectifier device 34' is capable of being triggered. But, once the alarm has been trigger, should switch 52 be placed in its disarm position, the silicon controlled rectifier will continue to operate because the current supplied to it will not be interrupted by placing switch 52 in its disarm position. To this end, switch 52 is connected between the positive electrode of battery 30' and contact 40'. As above, when switch 52 is placed in its arm position, electrical power is available to trigger silicon controlled device 34' when the mercury switch 38' closes contact 40' and 42'. Therefore, switch 52 must first be placed in the arm position before the silicon controlled rectifier 34' is triggered into its conducting state, sounding alarm 32'.
Rather than using the key operated switch to silence the alarm, a "tough" switch 53 is utilized including a solid-state circuit which is energized when two contacts 62 and 64 are simultaneously touched with moistened finger tips. The touch switch can be completely concealed in the design of the alarm unit so that its presence is undetectable to the uninformed observer. The semi-conductor circuit includes a Darlington type amplifier 54. A Darlington amplifier comprises cascaded transistors providing an extremely high input and extremely low output impedance and having a high current gain. The collector of NPN transistor 56 is connected to the collector of NPN transistor 58. The emitter of transistor 56 is connected to the base of transistor 58, while the base of transistor 56 is connected through a limiting resistor 60 to touch contact 62. The emitter of transistor 58 is connected to the cathode of silicon controlled rectifier 34', while the collectors of transistors 56 and 58 are connected to the anode of rectifier 34'. Contact 64 is connected to contact 40' of the mercury switch 38'. To conserve space, the Darlington amplifier may be a monolithic type integrated circuit of which a General Electric type 2N5306 is typical. Other suitable amplifier/switching devices may be utilized.
Normally, the Darlington amplifier 54 is not active. In order to silence the alarm after it has been triggered, moistened finger tips are applied to the touch contacts 62 and 64. When the touch contacts are so bridged, a minute direct current is applied through the skin resistance to the base of transistor 46. This current is sufficient to cause the Darlington amplifier to conduct, thereby shunting current away from silicon controlled rectifier 34' and sufficiently impeding the current flow through the rectifier causing it to be non-conductive. When the fingers are subsequently removed from contacts 62 and 64, the current flowing through the alarm 32' is interrupted, silencing the alarm. To the unwary intruder, who may attempt to silence the alarm by turning the switch 52 to its disarm position, the continuing sounding of the alarm can only cause panic, thereby being thrown into the desired state of disorientation which will hinder his escape.
A plurality of "touch" switches may be included in the circuit to heighten the complexity of the turn-off function. These switch circuits may be so arranged that coincident operation is necessary. Of they may be so configured that one circuit will negate the function of the other when both are simultaneously activated. The meaning of the switching function would be construed broadly to include such alternatives.
With the alarm circuit shown in FIGS. 3 or 4, the device may be manually carried from place to place without triggering the alarm by placing the switches 36 and 52 to the disarm position, thus preventing current from flowing through alarm devices 32 and 32' and triggering silicon controlled rectifiers 34 and 34' respectively.
The assembly diagram of the device presented in FIG. 2 includes the components shown in FIG. 4. The silicon controlled rectifier 34' is mounted to support plate 18 and resistors 44' and 50' are connected to the silicon controlled rectifier device and are located between support plates 16 and 18. Capacitor 46' is also located between the support plates. Darlington device 54 is attached to support plate 18, while mercury switch 38' is attached between support plates 16 and 18. Resistor 60 is also connected between the support plates while master switch 52 is connected to the housing 12 of the alarm device. While the arrangement of the components shown in FIG. 2 enables the device to be assembled and housed completely within housing 12, other physical arrangements for the components may be devised by those of ordinary skill in the art.
While the above described alarm device 10 can be used as a security alarm protecting against unwary intruders, it may also be used as a fire detection alarm. To achieve this, a thermally actuated bi-metallic, normally open, switch paralleling the mercury switch may be included. Thus, when a substantial heat rise of the ambient air occurs, the bi-metallic switch contacts close, triggering the alarm in the same manner as the above described mercury switch.
While a single alarm unit has been described above, it should be noted that a number of similar independent units may be placed at strategic locations, each being capable of being altered in position, creating an alarm system providing security for a relatively large area. The units designated 70, 72 and 74, when triggered, may produce an audible or inaudible alarm. When an inaudible alarm is produced, suitable transducers 76 and 78 tuned to pick up the inaudible alarm signal, activate a central monitoring system 80 which in turn activates a main alarm 82 or any of a plurality of remote alarms 84. Each transducer is tuned to an alarm frequency of, for instance, 2,800 Hertz while transducers 76 and 78 reject other frequencies. Suitable means for discriminating between the true alarm signal and a random, unwanted signal of like frequency could be provided in the central monitor, wherein coincident reception of the desired frequency signal and an accompanying pulse modulation or audio modulating frequency would be required before the central monitor would activate the main alarm system. This would prevent "nuisance" alarms. A modulated ultrasonic or radio frequency transmission system may be used between the alarm devices, transducers 76 and 78 and central monitor system 80. The central monitor may activate such remote and local alarms as telephone dialers, alarm bells, lights or other similar warning devices. In the case of an audible system, suitable transmission techniques are employed to prevent the central monitor from picking up extraneous noise signals, and, to this end, the alarm signal produced by alarm units 70, 72 and 74 may be at a fixed frequency of 2800 Hertz modulated at a 3 to 5 Hertz rate. It is impossible that a similar extraneous noise signal, having these characteristics, will be produced, thus insuring that the central monitor will be responsive only to the actual triggering of an alarm unit. Because the alarm units 70, 72 and 74 are portable, their positions may be changed nightly, thus preventing "casing" of the protected area by even the most skillful burglar. The entirely passive nature of the alarm units, when armed but not activated, also enhances the effectiveness of the system by giving no sign of their presence or location.
It may be seen that the above objects are efficiently accomplished and obtained by the principles of the present invention. Further, the above description merely illustrates the principles of the present invention and should not be construed in a limiting sense. To that end, therefore, the invention should be accorded its full scope of protection to which it is entitled by this patent application.