SECURITY SYSTEM AND CONTROL CIRCUIT
First Claim
1. 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 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 activate-deactivate 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 deactivate 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.
0 Assignments
0 Petitions
Accused Products
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.
2 Citations
9 Claims
-
1. 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 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 activate-deactivate 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 deactivate 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.
- means for generating an activate-deactivate signal;
-
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 sensor circuit 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.
- 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
-
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 activate-deactivate 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 activate-deactivate signal is reapplied thereto.
Specification