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Publication numberUS3839711 A
Publication typeGrant
Publication dateOct 1, 1974
Filing dateJan 28, 1972
Priority dateApr 2, 1970
Publication numberUS 3839711 A, US 3839711A, US-A-3839711, US3839711 A, US3839711A
InventorsCollins T, Lee J
Original AssigneeMinnesota Mining & Mfg
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Security system and control circuit
US 3839711 A
Abstract
A control circuit for activating and deactivating a security system without production of an alarm by the security system when a security sensor of the system is indicating an alarm condition at the time the system is activated. The security system is of a type which produces an alarm in response to an alarm signal which lasts a predetermined time. The control circuit comprises a bistable toggle device for activating (when in a first state) and for deactivating (when in a second state) an alarm sensor circuit of a security system. The toggle device has at least one input and is responsive to an activate-deactivate signal at its input to switch from its state prior to the arrival of the activate-deactivate signal to the other of its states. An initial alarm sensor circuit resets the toggle device from its first state to its second state if an alarm condition is sensed within a predetermined duration less than the predetermined time after activation of the system.
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Description  (OCR text may contain errors)

Collins et al.

SECURITY SYSTEM AND CONTROL CIRCUIT Inventors: Thomas E. Collins, East Oakdale;

John H. Lee, Woodbury Township, Washington County, both of Minn.

Minnesota Mining and Manufacturing Company, St. Paul, Minn.

Filed: Jan. 28, 1972 Appl. No.: 221,838

Related US. Application Data Continuation of Ser. No. 25,166, April 2, 1970, abandoned.

Assignee:

US. Cl 340/286, 340/276, 307/289, 307/293 Int. Cl. G08b 23/00 Field Of Search 340/276, 286, 213, 309.1; 315/84; 307/247 R, 313, 293,289, 99

References Cited UNITED STATES PATENTS I Oct. 1, 1974 3,585,584 6/l97l Behrcnd 340/276 3.588,865 6/197] Hansen 3,594,768 7/l97l Harris 340/276 Primary ExaminerJohn W. Caldwell Assistant Examiner-William M. Wannisky 5 7 ABSTRACT A control circuit for activating and deactivating a security system without production of an alarm by the security system when a security sensor of the system is indicating an alarm condition at the time the system is activated. The security system is of a type which produces an alarm in response to an alarm signal which lasts a predetermined time. The control circuit comprises a bistable toggle device for activating (when in a first state) and for deactivating (when in a second state) an alarm sensor circuit of a security system. The toggle device has at least one input and is responsive to an activate-deactivate signal at its input to switch from its state prior to the arrival of the activatedeactivate signal to the other of its states. An initial alarm sensor circuit resets the toggle device from its first state to its second state if an alarm condition is sensed within a predetermined duration less than the predetermined time after activation of the system.

9 Claims, 1 Drawing Figure PAIENIEBHBH um Mi. 3H J EW w 5% l m WM Hon. T

BY M ATTORNEY;

, 1 SECURITY SYSTEM AND CONTROL CIRCUIT This is a continuation of application Ser. No. 25,166 filed Apr. 2, 1970 and now abandoned.

BACKGROUND OF INVENTION The invention relates in general to security systems of the type which produce an alarm in response to an alarm signal of at least a predetermined time. More particularly, the invention relates to control circuits for activating and deactivating a security system, and for preventing production of an alarm by the system when a security device of the system is in an alarm condition at the time the system is activated.

An example of such a security system is a combined fire-intrusion system comprising a plurality of smoke and heat sensors and a plurality of intrusion sensors such as pressure mats, window locks, and door locks. Commonly, these security sensors are coupled in electrical loops, with the heat sensors coupled together in at least one loop and the intrusion sensors being similarly coupled in at least one other loop. An alarm sensor circuit is coupled to a reference point in each loop and produces an alarm signal in response to an abnormal potential at the reference point. Abnormal potentials are produced at the point when a security sensor in a loop assumes an alarm condition.

In US. Pat. No. 3,286,250 there is described a security system which includes a security sensor which must necessarily be in an alarm condition when the system is activated. The system described is a burglar alarm system for protecting a building. The system includes door and window locks. The security sensor which is in an alarm condition when the system is turned on is the door lock of the door through which a person would leave the building after activating the system. The patent teaches a circuit whereby this door lock is bypassed from the time the system is first activated until after the door is closed to permit a person to activate a system and then leave through the door without producing an alarm. Such a system solved the problem of a door lock producing an alarm each time the system was activated. However, with such a system an alarm is still produced if any other security sensor is in an alarm condition at the time the system is activated.

It is often desirable to activate a security system from any of several locations. E.g., in a system for protecting a residence, some prefer to activate a system from their bedroom before retiring for the night and it is of course convenient to be able to activate the system at each of the exits, there quite often being several. There are also advantages to being able to activate and deactivate a system from outside the residence.

SUMMARY OF THE INVENTION The present invention eliminates the disadvantage of the prior art system which produces an alarm upon activation of a security system when a security sensor is in an alarm condition, and at the same time provides a control circuit which can be economically and practically actuated from each of a plurality of locations.

Briefly, the control circuit of the present invention comprises a bistable toggle device for activating (when in a first state) and for deactivating (when in a second state) an alarm sensor circuit of a security system. The toggle device has at least one input and is responsive to an activate-deactivate signal at its input to switch from ous signal lasting less than a prescribed time from altering the toggle device state.

BRIEF DESCRIPTION OF DRAWINGS The invention will be further understood upon reading the following description in which:

FIG. 1 is a partial block diagram and schematic circuit diagram illustrating a preferred embodiment of a control circuit of the present invention.

DETAILED DESCRIPTION In FIG. 1 an electrical loop and an alarm sensor circuit of a security system are shown as 10 and 12 respectively. Electrical loop 10 is shown to comprise security sensors 14, 16, 18, 20 and an impedance element 22 for I terminating the loop. The security sensors are illus-. trated as switches, sensors 14 and 18 being of the powered type, and switches 16 and 20 of the non-powered type. Examples of powered security sensors are infrared light beam and motion detectors, whereas door locks, window locks and window tapes are nonpowered type security sensors. The switch positions shown are their normal non-alarm positions. It will be appreciated that with all of the security sensors in a non-alarm condition, the electrical condition, i.e., the potential, current flow, or impedance, at reference point 24 will be normal, whereas if any one of the security sensors is in an alarm condition, the electrical condition at reference point 24 will be abnormal. A lamp 25 is provided as a means for indicating when a security sensor of the system was indicating an alarm condition at a time when the system was activated. Reference point 24 is coupled by lead 26 as the input to alarm sensor circuit 12. The output of alarm sensor circuit 12 is provided on leads 28 and 30.

The control circuit of the present invention is shown to comprise means 32 for generating an activatedeactivate signal, a bistable toggle device 34, and an initial alarm sensor circuit 36. For the preferred and exemplary embodiment shown, the activate-deactivate means 32 comprises a plurality of switches 38 and a timer circuit 40. Depression of any one of the switches 38 for at least a prescribed time will cause timer circuit 40 to produce an activate-deactivate signal which is coupled on lead 42 as the input to toggle device 34.

Toggle device 34 is shown to comprise a bistable flipflop shown generally as 44 having a pair of crosscoupled NPN transistors 46 and 48 and a steering network shown generally as 50 coupling the bases of said cross-coupled transistors to lead 42. Toggle device 34 also includes a relay 52 controlled by an output of the flip-flop 44. The relay is coupled between the source of electrical potential 54 by lead 56 to electrical loop 10, by lead 58 to initial alarm sensor circuit 36 and by lead 60 to alarm sensor circuit 12. It will be appreciated that with the toggle flip-flop in a first state, that is with transistor 46 nonconducting and transistor 48 conducting, relay 52 will be pulled in and the source of electrical potential 54 will be applied to the security sensors of electrical loop 10, to the initial alarm sensor circuit 36 and to alarm sensor circuit 12. It should be noted that for purposes of the present invention it is not essential that the security sensors, the initial alarm sensor circuit, and the alarm sensor circuit be powered by the same relay or even the same source of potential. As will become more fully apparent, from the discussion which follows it is only necessary that the output state of toggle device 34 deactivate alarm sensor circuit 12 if an alarm condition is sensed within a predetermined duration after the system is activated. The predetermined duration must be less than the minimum predetermined time during which an alarm signal must persist in order to produce an alarm.

Initial alarm sensor circuit 36has an input via lead 28, the output of alarm sensor circuit 12. The output of the initial alarm sensor circuit appears on lead 62 which is coupled to the base of transistor 46 of flip-flop 44. As previously stated, the function of initial alarm sensor circuit 36 is to reset flip-flop 44 in the event that a security sensor is indicating an alarm condition upon activation of the security system. The manner in which this is accomplished will now be described.

The system is activated by depressing any of switches 38. Assuming the system was initially in a deactivated state. transistors 64 and 66 of timer 40 will be nonconducting, and the potential of the signal coupled on lead 42 to the input of toggle device 34 will be at about the potential of potential source 54. When the switch 38 has been depressed for a prescribed time, the capacitors of timer 40 will have charged to a level sufficient to forward bias transistor 66 which will in turn cause transistor 64 to conduct whereupon the potential on lead 42 goes towards ground potential. A signal of negative going potential is seen by toggle device 34 as an activate-deactivate signal and causes it to change states. Since it was assumed that the system was initially deactivated, the appearance of the negative going potential signal at the input to toggle flip-flop 44 will cause transistor 48 to switch from a non-conducting to a conducting state to pull in relay 52. When relay 52 is pulled in the potential source 54 is applied to the combination of electrical loop 10, initial alarm sensor circuit 36, and alarm sensor circuit 12. With power now applied on lead 58 to initial alarm sensor circuit 36, capacitor 68 will begin to charge. lf none of the security sensors are indicating an alarm condition, the electrical condition at reference point 24 will be normal, lamp 25 will be lit and transistor 70 of the alarm sensor circuit 12 will be in a conducting state. With transistor 70 conducting, the alarm sensor circuit output on leads 28 and 30 will be relatively low indicating a non-alarm condition. With a low potential appearing at the emitter of transistor 72 of the initial alarm sensor circuit 36, that transistor will be reverse biased.

On the other hand, if a security sensor is in an alarm condition when the system is activated, an abnormal condition will be present at reference point 24 and transistor 70 of the alarm sensor circuit 12 will be in a non-conducting state. Accordingly, the potential at the emitter of transistor 72 of the initial alarm sensor will be at a relatively high potential, and will be greater than the potential at the base of transistor 72 to forward bias transistor 72. With transistor 72 conducting, a reset signal is coupled via lead 62 to the base of transistor 46 of flip-flop 44 causing transistor 46 to switch from a non-conducting to a conducting state thereby resetting the flip-flop and deactivating the system. Lamp 25 is not lit to thereby indicate that the system has been automatically deactivated. When the alarm condition indicated by a security sensor is removed, the system must be reactivated by at least reapplying an activatedeactivate signal to the flip flop 34.

It will be appreciated by one skilled in the art that the component values of capacitor 68 and of the charging and bias resistors of initial alarm sensor circuit 36 can be so selected such that a predetermined duration after activation of the system, the potential appearing at the base of transistor 72 will be greater than the potential on lead 28 for a non-conducting state of transistor 70. Accordingly, the initial alarm sensor circuit 36 will not respond to an alarm signal on lead 28 to reset toggle device 34. An alarm signal will then be permitted to appear on lead 30 for so long as an alarm condition is being indicated by a security sensor of electrical loop 10.

While there has been described what at present are considered to be, the preferred embodiments of the invention, it will be understood that various modifications may be made therein which are within the true spirit and scope of the invention. E.g., if the convenience and economies offered by the toggle device illustrated, which device permits any of a plurality of switches coupled between only a single pair of conductors to both activate and deactivate a system, are not desired, the toggle device may take the form of a conventional set-reset flip-flop. The flip-flop set input would be coupled to one or more means for generating an activate signal. The flip-flop reset input would be coupled through a logical OR function circuit to both the initial alarm sensor circuit output and to at least one means for generating a deactivate signal. All such modifications, improvements and the like are considered to be within the scope of the appended claims.

What is claimed is:

1. In a security system having an alarm sensor circuit which when activated provides an alarm signal in re sponse to an indication from a security sensor of an alarm condition and which system produces an alarm in response to an alarm signal which lasts a predetermined time, a control circuit for deactivating the security system when a security sensor of the system is indicating an alarm condition at the time the system is activated, comprising:

means for generating an activate-deactivate signal;

a bistable toggle device for providing an output signal respresentative of the state of the toggle device to the alarm sensor circuit, the output signal of a first state of the toggle device operating to activate the alarm sensor circuit and the output signal of the second state of the toggle device operating to deactivate the alarm sensor circuit, the toggle device having at least one input and being responsive to an activate-deactivate signal at said input to switch from its state prior to the arrival of said activatedeactivate signal to the other of its states; and

an initial alarm sensor circuit coupled to said security sensor and to the toggle device for resetting the toggle device from its first state to its second state in response to an indication from said security sensor of an alarm condition occurring within a predetermined duration less than said predetermined time after activation of the system to thereby deac' tivate the alarm sensor circuit and prevent production of an alarm by the security system when said security sensor is indicating an alarm condition at the time of activation of the security system.

2. A control circuit according to claim 1 wherein a plurality of security sensors are connected in at least one electrical loop, each loop having a normal electrical condition at a reference point when each security sensor of the loop is in a non-alarm condition and having an abnormal electrical condition at the reference point when any security sensor of the loop is in an alarm condition, wherein the alarm sensor circuit is a switching circuit having an input coupled to said reference point, the switching circuit producing said alarm signal as a relatively high output signal whenever the electrical condition of the reference point is abnormal and producing a relatively low output signal whenever the electrical condition at said reference point is normal, wherein the toggle device includes a reset input, and wherein the initial alarm sensor circuit is responsive to a said relatively high output signal occurring within said predetermined duration following an activation of the system to couple a reset signal to the reset input of the toggle device to deactivate the system by resetting the toggle device from its first to its second state.

3. A control circuit according to claim 2 wherein the toggle device comprises a toggle flip-flop and a relay, the relay being controlled by an output of the flip-flop and coupled between a source of electrical potential and the combination of each electrical loop, the initial alarm sensor circuit and the alarm sensor circuit,the flip-flop operating the relay to apply the electrical potential to said combination when in a first state corresponding to the first state of the toggle device and operating'the relay to disconnect the electrical potential from said combination when in its other state.

4. A control circuit according to claim 3 wherein said toggle flip-flop comprises a bistable multi-vibrator including a pair of cross-coupled NPN transistors, a first one of which is non-conducting and the second one of which is conducting when said flip-flop is in its first state, a first diode having its anode coupled to a base lead of one of said transistors, a second diode having its anode connected to a base lead of the other of said transistors, a pair of series connected capacitors connected at one end of the pair to a cathode lead of one of said diodes and at the other end of the pair to a cathode lead of the other diode, and an input terminal for receiving a said activate-deactivate signal coupled to the common ends of said capacitors; wherein the alarm sensor circuit of the security system comprises an NPN transistor having a collector lead coupled to receive said electrical potential from said relay, having an emitter lead coupled to a ground potential and having a base lead coupled to an anode lead of a diode, the cathode of said diode being coupled to said reference point and to a base lead of a PNP transistor having an emitter lead coupled to receive said electrical potential from said relay and having a collector lead coupled to a point common to the cathode lead of said diode and the base lead of said NPN transistor, and an output lead coupled to the collector lead of said NPN transistor to carry said alarm signal when said NPN transistor is non-conducting; and wherein the initial alarm sensor circuit comprises a PNP transistor having an emitter lead coupled to said alarm sensor circuit output lead and having a base lead coupled to one lead of a capacitor, the other lead of the capacitor being coupled to ground and to receive said electrical potential from said relay, and having a collector lead coupled to the base of said first PNP transistor of said flip-flop;

the PNP transistor of the alarm sensor circuit residing in a conducting state when the security system is activated with no security sensor indicating an alarm condition to provide a nearly ground potential at the emitter of the initial alarm sensor circuit PNP transistor to reverse bias said PNP transistor but the alarm sensor circuit NPN transistor switching to a non-conducting state when said security sensor is in an alarm condition to couple a positive potential on said output lead to the emitter of the initial alarm sensor circuit PNP transistor, the potential at the base of the initial alarm sensor circuit PNP transistor being directly proportional to the time elapsed since said flip-flop was switched to an activated state and being less than the positive potential at the emitter of said initial alarm sensorcircuit PNP transistor if said elapsed time is less than said predetermined duration to forward bias said initial alarm sensor circuit PNP transistor to in turn switch said flip-flop from its activated to its deactivated state.

5. A control circuit according to claim 1 wherein the means for generating an activate and deactivate signal comprises at least one switch and a timer circuit in series between the input to said toggle device and said switch, operation of said switch for at least a prescribed time causing the timer circuit to produce and couple to the toggle device input an activate-deactivate signal to prevent improper activation or deactivation of the system by a spurious signal of a duration less than said prescribed time.

6. A security system according to claim 1, further comprising means for indicating whether the alarm sensor circuit is activated thereby indicating whether an alarm condition is indicated by said security sensor within said predetermined duration.

7. In a security system having an alarm sensor circuit which when activated provides an alarm signal in response to an indication from a security sensor of an alarm condition and which system produces an alarm in response to an alarm signal which lasts a predetermined time, a control circuit for deactivating the security system when a security sensor of the security system is indicating an alarm condition at the time the security system is activated, comprising a bistable device operative in a first state only upon an activate-deactivate signal being applied to said device for providing an output signal to activate the security system and operative in a second state to terminate said output signal to deactivate the security system; and

an initial alarm sensor circuit coupled to said security sensor and to the bistable device for resetting the bistable device to its second state to terminate said output signal and thereby deactivate the security system in response to an indication of an alarm condition from said security sensor when said alarm condition exists at the time of activation of the security system and for preventing the bistable device from returning to its first state until the activate-deactivate signal is reapplied thereto.

8. A control circuit according to claim 7, wherein the initial alarm sensor circuit comprises means responsive to the absence of an alarm condition at the time of activation of the security system inhibiting the initial alarm sensor circuit from resetting the bistable device to its second state.

9. In a security system having an alarm sensor circuit which when activated provides an alarm signal in response to an indication from a security sensor of an alarm condition and which system produces an alarm in response to an alarm signal which lasts a predetermined time, a control circuit for deactivating the security system when a security sensor of the security system is indicating an alarm condition at the time the security system is activated comprising first circuit means operative only upon an activatedeuctivate signal being applied to the system for activating the security system, and second circuit means coupled to said security sensor for receiving indications therefrom and coupled to the first circuit means for operating the first circuit means to deactivate the security system when the indication of an alarm condition is received by the second circuit means from said security sensor at the time of activation of the security system and for preventing the first circuit means from thereafter activating the security system until said activatedeactivate signal is reapplied thereto.

* l l l

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3286250 *Oct 16, 1964Nov 15, 1966Teitelbaum MenasheBurglar alarm utilizing bi-stable electronic switches
US3449738 *Jun 15, 1966Jun 10, 1969Jeron Electronics IncElectronic security system
US3531793 *Jun 13, 1967Sep 29, 1970Shottenfeld RichardBurglar alarm system
US3549892 *Dec 17, 1968Dec 22, 1970Detection Systems IncPhotoelectric circuitry for passive detection systems
US3585584 *Feb 14, 1969Jun 15, 1971Gene E BehrendIntruder detector and warning system
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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5555454 *Sep 3, 1994Sep 10, 1996Dees; Kent L.Remote security light signal alert system
US6137402 *Mar 4, 1999Oct 24, 2000Pittway Corp.Method for arming a security system
Classifications
U.S. Classification340/506, 340/528, 340/578, 327/220
International ClassificationG08B29/00, G08B29/10
Cooperative ClassificationG08B29/10
European ClassificationG08B29/10