Intruder detection and deterrent system

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BACKGROUND OF THE INVENTION

The present invention is related to intrusion detection systems and more specifically involves a system for both detecting intruders and for presenting signals to the intruders to deter them from further depth of intrusion.

Many detection systems including alarms and automatic locking systems are disclosed in the prior art. These systems are directed solely toward the objective of detecting an intrusion after the fact and generating an alarm to some point distant from the intrusion. None of the conventional devices has as a primary function the prevention of further intrusion by the burglar or unwanted visitor. Most of the prior art devices available today consist of what is known as "perimeter systems". The typical perimeter system comprises a ring of detection devices around an area such as a home or business providing a single line of defense. Usually these detection devices comprise switches connected to a central alarm system to indicate to the occupants that the perimeter system has been violated. The disadvantages of this system are severe. One such disadvantage is that the system gives no warning until the intruder has penetrated the protected area. At this time a relatively defenseless homeowner may be faced with an armed intruder bent on committing crimes of burglary, or worse, within the homestead. Another disadvantage is that once this type of system is tripped, it cannot reset unless all switches happen to return to their normal state. One example of a typical perimeter system alarm is that disclosed in U.S. Pat. No. 4,206,450 to Harden, et al. This patent discloses a perimeter fire and burglar alarm system having a series of sensors wired around the perimeter utilizing timers to allow the time of the alarm to be set or to allow the owner of the alarm to set the alarm and leave without tripping it. Once any one of the sensors is tripped by any of the expected events, such as intrusion or fire, the system immediately goes into the alarm mode, or else after a set time period goes into an alarm mode. This system can provide no further action with respect to the intrusion or fire. Thus, the Hardin patent discloses a standard perimeter alarm system adapted to provide a single alarm signal in response to a single sensed event.

Another example of a perimeter system providing a single alarm signal is that disclosed in the Burney patent, U.S Pat. No. 3,543,261. Burney discloses a single alarm system having a spacially separated set of sound detection sensors which are adjusted to avoid false alarms. Another example of a single alarm perimeter system is that disclosed in U.S. Pat. No. 4,385,287 to Eatwell. Although the sensors and the signaling apparatus are more sophisicated than that of conventional devices, the system is still a single alarm perimeter type system.

The patent to Boyko, U.S. Pat. No. 3,599,195, discloses a dual alarm intrusion detection system which utilizes motion sensors and heat/smoke detectors. The Boyko alarm utilizes only two alarms. One sensor can actuate both alarms. This system can detect intrusion only, or fire only, and has no sensor lockout, or capability for further detection after a sensor has been tripped. The patent to Ferrigno, U.S. Pat. No. 3,221,317, discloses a battery operated sensor system which senses moisture or other conditions and generates a sound signal through a public address system speaker. The patent is directed to a battery saving feature of this simple perimeter system. The system is intended to primarily convert natural phenomenon such as moisture or lightning, or changes in brightness, sound, voltage, current, and other natural phenomenon directly into electrical currents which then may be converted to audible signals. The patent to Forbat, U.S. Pat. No. 3,979,740, discloses a monitoring system which can be used as an intruder alarm. The system is primarily designed to prevent the generation of false alarms. The system is a perimeter system that has the capability of counting a number of intrusion pulses during a set period of time and then actuating a single alarm. The system has various means to filter out false signals. The system is limited in that once it has determined that an intrusion has occured it is limited in response to a single alarm.

U.S. Pat. No. 3,261,009 to Stetten, et al. is directed to a personnel sensing device utilizing seismic sensors. This system features filters for reducing false signals and utilizes timing circuits to respond only to a predetermined pattern of seismic signals. Once the system has determined or "recognized" the predetermined pattern, a single alarm is generated.

The patent to Galvin, U.S. Pat. No. 4,195,286, discloses a simple two stage system utilizing a single sensor to set off a first stage and two sensors to set off a second stage. The Galvin system requires both stages to go off almost simultaneously. The defect in this system is that the activation of a second stage at a spaced interval from the first stage will not provide the proper alarm response. Also if a single sensor is disabled no further capability is recognized in the system. The primary object of the Galvin system is to provide "overlapping coverage". The patent to Buckles, U.S. Pat. No. 3,900,841, discloses a purely mechanical system utilizing mechanical timers, gear systems, and screw drives. Also cams, switches, and motors are utilized. The Buckles system is slow to respond to multiple stimulations because of the mechanical drive. Also any sensor which is activated will continue to drive and actuate the entire system. It cannot be reset with any open or disabled sensor. The Buckles system is not satisfactory for an external perimeter system. It utilizes a "free period" when no alarm is given. Also the Buckles system lacks the ability to totally reset the timers because of its mechanical linkage. Also the system resets only if all sensors are in their normal position. Thus the Buckles system is a very inflexible unreliable system because of the purely mechanical timed actions of the system. Very little adjustment can be achieved with the Buckles intrusion system. The Buckles system also lacks the deterrent capabilities of the present invention.

All of the aforementioned conventional alarm systems suffer from the disadvantages that they generally rely upon a single, or at most, a double tripping of external sensors. They suffer from a further disadvantage that the alarm generated in response to the one or two sensors is a single alarm and usually occurs after the undesirable intrusion has occured. The conventional systems offer no deterrent capabilities for preventing the undesired intrusion. Furthermore the systems lack automatic resetting capabilities after one or more of the sensors have been tripped.

SUMMARY OF THE INVENTION

Currently available burglar alarm devices employ some sophisicated circuitry to coding, delay options, and/or telephone system interfacing. These units do not however employ logic in determining the presence of unauthorized persons on the protected premises. Perimeter protection systems, whether wireless or hard-wired, do not report or alarm until the perimeter is violated. This results in damage to the premises and possibly even to its occupants before the alarm sounds and other programmed actions can begin. Also this type of system cannot reset itself if the forced entry causes a switch to remain opened or closed (depending on the type circuit employed) and the property owner is then unprotected, even though the system may be very sophisticated, if just one switch is left in a tripped position. These systems require a resetting of sensors to their original position and repairing the damage done during the forced entry and also the resetting of the alarm to again have the protection the property owner intended. Placing sensors outside the home perimeter using conventional systems would also result in numerous unacceptable false alarms from stray dogs, cats, children, birds, and other sources which would also result in disabling the system until the circuits are restored after each triggering. Automatic phone-in devices to police departments and security bureaus would also be accidentally activated in cases where no actual entry has been attempted or intended. Thus, people employing such conventional systems must accept the fact that the sensors must be located so that the system will not alarm until forced entry and associated damage has occurred; the system may not reset after such an event depending on the condition the perimeter wires and switches are left in; and the security cannot be assured after an alarm sounds without a knowledgable person verifying the condition of the structure, the premises, and the alarm system wiring.

Thus, the present invention provides a system which may be utilized either as a supplement to a standard peripheral wired system or it may be used alone as an intrusion detection and deterrent device. The present invention discloses a logic device that detects and reacts to an intruder before he actually intrudes into the protected area. The logic function of the system insures that alarms are not sounded for normal access activities such as mail delivery, meter readers, salesmen, children, animals, and the like. Also the system discloses adjustable timers in the logic circuit to enable the system to be tuned to each specific protected area and security problem to provide an optimum level of protection not available through any currently available security system. The tuning of the system reduces or eliminates nuisance alarms while still providing early detection as well as early deterrence of the intruder.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram indicating the logic circuit for one embodiment of the invention.

FIG. 2 is a circuit diagram illustrating solid state electronic components which can be used to obtain the embodiment of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The logic system employed in this unit is based on the following assumptions and generalizations:

(1) Most thieves and intruders prefer to enter a home or business property when the owners are absent and they will go to extraordinary lengths to insure that the property is vacant before entering.

(2) The intruder will most likely have some pretense or excuse for being present on the property, for example, as a salesman or charity worker he will normally make his initial approach to the front door.

(3) The intruder does not normally employ forcible entry without first checking to see if a door or window has been left open which would allow easy entry and a possible alibi.

(4) The intruder will not remain outside the home for an extended period of time before attempting a forced entry in order to minimize his chances of being observed.

(5) If a potential intruder believes strongly enough that there may be someone in the home or business he will more than likely look for another place to burglarize.

(6) If an alarm sounds or the burglar fears he has been detected before he has committed a crime he will probably leave the premises without doing so.

The present system utilizes detection devices for inputs to a logic system which can be varied to suit each particular application. Simple reed switches which may be magnetically actuated can be placed on screen doors, storm doors, window screens, and other perimeter entry areas around a building or home. Also sensors or switches can be wired in conjunction with doorbells, gates, and pressure switches on the porch or sidewalk area to a home or building. Other sensors can be utilized in conjunction with a telephone since intruders often call a business or home to determine if there is anyone present. Other sensors such as motion detectors, infrared detectors, lighting detectors, pressure sensitive mats, trip wires, sound actuated switches, vibration actuated switches, or any other type of detector can be located at various locations out from the edge of the building or home.

Actual location of detectors, as well as the selection of detector types, can be determined by the structure to be protected. As an example, a person utilizing the system may wish to protect the average residential home having an attached garage, a screen patio, a fenced backyard with gates, storm doors, and screened windows. Detectors can be placed in such areas as the doorbell switch, gate switches, screen doors, and window screens. One key feature is to determine the paths of probable entry by a potential intruder and to place sensors along each potential path to detect activity in multiple areas and provide staged responses to the pending intrusion.

The multiple switch concept of the present invention thus allows a multiple response to a series of access paths attempted in a pending intrusion. As an example, if sensors are established on the doorbell, the front screen door, and the rear screen door of a residence, the system will elevate its status when the potential burglar rings the doorbell to determine if anyone is at home. No noticeable response will be triggered at this stage.

If the potential intruder then opens the screen door to gain access to the front door either to knock or check the security of the door, the sensor in the screen door can then activate a second stage function to provide a noticeable response such as turning on the interior lights in the home or turning on the porch light. Alternative responses could be the initiation of a tape recording of a dog barking or other audible response inside the home. Hopefully this response would serve to deter further attempts because of the intruders belief that someone may be home. Should the intruder still not be deterred and continue to check for other access paths, sensors located in his paths to the other possible entry points will provide further deterrence. Activation of a third sensor switch will serve to initiate an audible alarm which may also be tied in by telephone and/or radio signals to a central security station. Alternatively, the third sensor could activate another response and leave the audible alarm for a fourth activation. Thus the present invention utilizes a set of multiple sensors placed along the possible paths of intrusion to provide staged responses hopefully to deter the final intrusion into the protected area.

Referring now to FIG. 1, a preferred embodiment of the system is illustrated in the logic flow diagram. In this system five input sensors are utilized and denoted as A, B, C, D, and E. Each input sensor, which could comprise a normally closed magnetic reed switch or any one of the aforementioned types of sensors, is functionally connected to an input filters 10-14. These filters serve to isolate the sensors from the logic and activation circuits in order to filter out "noise" and extraneous signals possibly picked up by the wiring of the sensors or any of the sensor metallic components.

Each input filter 10 through 14 is connected to the set terminal of a flip-flop 15 through 19. The output of each flip-flop is connected by a capacitance element 20 through 24 to the inputs of an OR gate 25. The single output from the OR gate 25 is transmitted to a junction 26. One lead from junction 26 is connected to recycle timer 27. The output of timer 27 connects to adjustable timer 28 having an adjustment circuit 29 therein. The second lead from junction 26 passes to a second junction 30 having a first lead going to an AND gate 31 and a lead to AND gates 32 and 33. Each of the AND gates 31 and 32 has a single output communicated to time delays 34 and 35 respectively. The output of AND gate 33 is communicated directly to timer 36. The output of time delay 34 is communicated to timer 37 and the output of time delay 35 is connected to timer 38. Each of the timers 36 through 38 is an adjustable timer having manual setting means 39 through 41 thereon. The output of timer 28 is connected to the second input terminals of the AND gates 31 through 33. The output of timer 28 also is connected by line 42 to a pulse amplifer 43 which in turn is connected to the reset terminals of flip-flops 15 through 19.

A manual switch 44 is provided to allow the system to be deactivated and reset. Circuit 44 consists of a spring loaded switch with an "arm" (alarm system activated) position and a "clear/reset" (spring loaded) position to provide these two functions. When the switch is in the clear/reset position, timers 28, 36, 37 and 38 are cleared to their unactivated state and by means of pulse amplifier 43, the flip-flop elements 15 through 19 are reset to their untriggered state. When the switch is placed in the arm position, the alarm system is armed and ready for service.

The output of recycle timer 27 is also connected to timer recycle driver 45 having outputs to timers 28, 36, 37 and 38. The recycle driver outputs clear to zero the accumulated time of timers 28, 36, 37 or 38 that are in the process of a timing cycle.

It should be noted that the burglar deterrent system depicted in the logic diagram of FIG. 1 is arranged to provide a multi-stage response wherein the first stage is dedicated to "waking the system up" or placing the system in a "stage of increased alert". This is optional with the present invention and is utilized to avoid positive responses in the system to what would normally be considered false alarms such as pets, salesmen, meter-readers, etc. Thus by the dedication of the first stage of the system to merely placing the system at a higher degree of alert, such false alarms are effectively filtered out.

In typical operation, an intruder into a protected system having the elements illustrated in FIG. 1, would first activate one of the sensors A through E. This first stage activation of a single sensor might be the ringing of a doorbell or the opening of a gate in a fence surrounding the premises. As a result of the activation of the first sensor which as previously noted could be an entirely innocent activation by a well intentioned party, a signal is passed to the flip-flop 15 through 19 associated with the tripped sensor. This signal initates a change in state of the associated flip-flop output. The resulting signal generated by the change in the flip-flop state is passed through its associated capacitance element resulting in a pulse of signal at the input of OR gate element 25. The pulse passes through the OR gate 25 to junction 26 where it is routed to AND gates 31 through 33 and recycle timer 27. The pulse at junction 26 triggers recycle timer 27 starting its time cycle. The output of recycle timer 27 clears timers 28, 36, 37 and 38 to zero by means of timer recycle driver 45. Timer 27 also prevents undesirable cascading of signals in the system. At the conclusion of the time period of timer 27 the high-to-low signal transition at the output of timer 27 triggers timer 28. Timer 28 begins its timing in response to this signal from timer 27 and, during the amount of time which has been preset by adjustment 29, timer 28 generates an output signal to junction 47. This output signal is simultaneously transmitted to the AND gates 31, 32 and 33.

At this point in time one signal input sensor has been tripped, generating a single signal from OR gate 25, activating timer 28 and placing the system in an "alert" status. As long as timer 28 continues generating an output signal in response to the present adjustment 29, the system is in the aforementioned increased state of alert. Should a second sensor A through E now be tripped during the time cycle of timer 28, a second input signal is transmitted to the OR gate 25 which communicates the signal through junction 26 directly to AND gates 31 through 33. At this point in time, since all conditions for activating AND gate 31 are simultaneously fulfilled, an output signal is generated from AND gate 31 which passes through a time delay 34 and triggers adjustable timer 37, generating an output signal at output lead 48. This in effect, has activated stage two of the deterrent system. The system output for this activation is the closing of a relay contact to activate a device for providing some positive indication or action within the premises or outside the premises to deter any possible intruder who may be considering entering the premises.

Thus, the activation of the first stage and then an activation of an additional sensor within the time duration of timer 28 will initiate stage two response which can be tied into any deterrent element desired by the property owner. For example, it is believed that stage two could be connected to a porch light or an interior light such that when stage two is activated by timer 37, the aforementioned light could be turned on and a very strong deterrent created against further intrusion into the premises.

The activation of the second sensor also resets timer 28 to zero time by means of recycle timer 27 and recycle driver 45. If, during the timing period of timer 28 and timer 37 a third sensor is tripped, the signal from the third sensor moves through its respective flip-flop, OR gate 25, and junction 26 to combine with the output signals from junction 47 and timer 37 to activate AND gate 32. These three signals to AND gate 32 thus generate a signal through time delay 35 and timer 38, thereby activating stage three of the system. Stage three can be an even further or stronger response to the attempted intrusion such as dialing a predial alarm system or other deterrent activation. For example, stage three could turn on a radio or tape recorder inside the home or could be used as a combination action to do any of these actions in addition to turning on all exterior lights. The activation of the third sensor also resets timer 28 and timer 37 to zero time by means of the timer 27 and recycle driver 45.

A fourth sensor activation such as an actual entry into the home while adjustable timers 28 and 38 are running will serve to activate AND gate 33 thereby initiating the final stage of the deterrent system. Activation of the fourth sensor also resets timer 28, timer 37 and timer 38 to zero time by means of timer 27 and recycle driver 45. The final stage could be either an internal or external alarm or such an alarm combined with a phone-in warning system to a central alarm bureau.

Thus, the logic system disclosed in FIG. 1 provides a staged response to a multiple-point entry system. Each successive stage of the response is activated by stimulation of an additional sensor. Each stage is also related by time elements to the preceding stage such that seperate unconnected activations of the sensors normally will not combine to stage the alarm system into a higher deterrence level. The operation of the "alert timer 28" allows the system to automatically reset back to the unactivated condition following accidental or single intentional activations of the sensors. The reset of the system commences when timer 28 completes its time cycle as denoted by a change in its output from a high to a low signal level. This condition activates pulse amplifier 43 which generates a pulse that resets flip-flops 15 through 19. After receiving the reset signal, the flip-flops are ready to receive new trip signals from input sensors A through E. Reset of timers 36, 37 and 38 is accomplished by the timer completing its time cycle. If immediate termination of the timer cycle is desired, activation of switch 44 to the clear/reset position accomplishes this.

One distinct advantage of the present invention is that a burglar cannot pass by the homestead and set off the alarm then leave immediately and wait until a neighbor or policeman comes in and shuts off the alarm, then return later with a deactivated alarm to enter the premises undetected. Should this be attempted with this system, the alarms will have been automatically reset after preset time periods. Upon return of the burglar to the protected premises, entry would be detected and deterred by the sensors and alarms. If any sensors are left in an open position, negating their operation, the system will continue to function. It will count the open (tripped) sensors as a vote each time timer 28 cycles through; thus maintaining the system at the "alert" response level. With stage one thus operational, all additional inputs will trigger a response at one level higher than if all sensors were closed. As a result, some deterrent capability remains in the system as long as just one sensor remains operational and unactivated.

Referring now to FIG. 2, there is illustrated a circuit diagram containing the electrical components which can be utilized in one embodiment to form the invention disclosed in the logic circuit of FIG. 1. The input filter and isolation circuit 10 of FIG. 1 are represented in the phantom block 10 shown in FIG. 2. The particular electronic components comprising element 10 are a resistor 103 connected to a 5 volt DC voltage source, an input resistor 101, an inverter element 105 and a capacitor 104. When an input sensor is closed (untripped) the voltage divider action of resistors 103 and 101 result in a low signal level at the input of inverter 105. When the input sensor is open (tripped) the voltage at the inverter input is no longer divided by resistors 101 and 103, resulting in a high signal level at the input of inverter 105. Capacitor 104 operates in conjunction with resistors 101 and 103 to filter out undesirable noise signals that may be picked up by the sensor wiring. This combination of components forms the input filter and isolation element 10 of FIG. 1. A similar set of components is utilized to form similar filter and isolation elements 11 through 14. The output of element 10, (low signal when the sensor is open or tripped and high signal when the sensor is closed or untripped), is communicated to NAND gate 107. NAND gates 107 and 108 are connected together to form a bistable element known as an RS (reset, set) flip-flop which is an element having two stable states. Specific combinations of signals at the set and rest inputs will cause the flip-flop to change from one stable state to the other. The flip-flop filters out repeated signals at any one sensor so that only the first input signal activates the flip-flop output signal and subsequent activations of the same sensor are ignored unless the flip-flop has been reset by a signal from the reset circuity 155, 154, 157 and 156. The low signal received from inverter 10 as a result of the opening of the sensor A, sets the flip-flop, resulting in a change from a high signal condition to a low signal condition at junction 109. This transition of signal from high to low reacts with capacitor 110 to provide a momentary dip in applied voltage at junction 111. This dip or pulsation is read as a change from a high signal, to a low signal, to a high signal by NAND gate 112. It should be noted that the low signal from inverters 105 works in conjunction with a high signal in circuit 141 to set the flip-flop 107/108. Similarly, a high signal from inverter 105 works in conjunction with a low signal in circuit 141 to reset the flip-flop 107/108. Flip-flop elements comprising bistable elements having two NAND gates are utilized with sensors B through E, identical to those of sensor A as illustrated in FIG. 2. Likewise, each flip-flop output is connected through a capacitor and a voltage/resistance circuit to provide a single pulsed output as described with respect to sensor A and element 10.

The OR gate 25 of FIG. 1 is represented in actual components in the embodiment of FIG. 2 by the use of NAND gates 112 and 113 and NOR gate 114. Due to the continuous high signal arising from voltages 111, all of the inputs of the NAND gates 112 and 113 are continuously high, resulting in low outputs from the two NAND gates into the NOR gate 114. Due to the low outputs from the NAND gates 112 and 113, the output of the NOR gate 114 is continuously high.

The A signal generated by the activation of any of the sensors A through E will trip the relevant flip-flop and create a pulse in voltage 111 at the input of the corresponding NAND gate 112 or 113. The generated voltage pulse is sensed by one of the NAND gates 112 or 113 and, as a result, the condition for activating one of the NAND gates no longer exists. At this moment in time, the low signal pulse at the NAND gate input wil be converted to a high signal pulse at the corresponding NAND gate output. This high signal pulse will be transmitted to the NOR gate 114 input resulting in a low signal pulse at the NOR gate 114 output. Thus, the two NAND gates 112 and 113 in series with the NOR gate 114 serve the same function as the OR gate 25 of FIG. 1. A dip or pulse in voltage at any of the five inputs of NAND gates 112 and 113 is thus converted to a dip or pulse in voltage at the output of NOR gate 114. The output of NOR gate 114 is normally a high signal that is pulsed to a low signal condition for approximately 10 microseconds as a result of a sensor trip action setting a flip-flop. This low signal pulse is connected to NOR gate 115 which functions as an inverter element. The output of NOR gate 115 is a high pulse that is connected to an output of NAND gates 116, 117 and 134.

The low signal pulse from NOR gate 114 is also simultaneously transmitted to timer 118 which represents recycle timer 27 of the logic circuit of FIG. 1. The low pulse from NOR gate 114 triggers timer 118 having a time duration of approximately 0.1 seconds. The output of timer 118 is transmitted to transistors 143, 144, 145 and 146. These transistors and associated base resistors comprise the timer recycle driver 45 of FIG. 1. The time duration of timer 118 is sufficient to allow the timer recycle driver transistors 143,144, 145 and 146 to discharge to zero the timing capacitors 150, 151, 152 and 153.

The output of timer 118 is also transmitted by junction 120 to timer 119 via capacitance element 147. At the conclusion of the time period of timer 118, the high-to-low signal transition triggers timer 119, starting its time cycle. The output duration of timer 119 is set by timing capacitor 150, resistor 142 and adjustable resistor R.sub.A1. The output signal is a high signal and results in a timed high output at junction 124. This high output is communicated by lead 125 to the input terminals of the three NAND gates 116, 117 and 134, thus providing a high level input signal at these NAND gates. This input signal is maintained during the entire timing cycle of timer 119. Timer 119 comprises the first stage or "increased alert" stage of the deterrent system corresponding to element 28 of FIG. 1. The duration of increased alert is set by the action of timer 119 which can be adjusted by the operator of the system through the use of adjustable resistor R.sub.A1. As long as timer 119 is running, the high signal communicated by NAND gates 116, 117 and 134 provides a high signal at one terminal to each of these gates.

During the generation of a high signal by timer 119, should a second sensor A through E be activated, a low signal pulse will be generated from NOR gate 114 which in turn causes a high signal pulse at the output of NOR gate 115. The high signal pulse from NOR gate 115 is applied to the second terminal of NAND gates 116, 117 and 134. This high signal pulse combined with the high signal output from timer 119 causes a low output from NAND gate 116 which triggers timer 126. Simultaneously, the low signal pulse from NOR gate 114 also triggers timer 118.

As mentioned previously timer 118 activates the timer recycle driver transistors 143, 144, 145 and 146 which discharges timing capacitors 150, 151, 152 and 153, thereby resetting the corresponding timers to zero. Then the accumulated time period in timer 119 is reset to zero and it restarts its timing cycle. NAND gates 117 and 134 do not respond to the high signal pulse from NOR gate 115 since less than the required three input high level signal conditions exist at that point. Timer 126 has a short timing cycle of approximately 1 millisecond to prevent undesired cascading of signals to NAND gates 117 and 134. At the conclusion of the timer 126 timing period, the high-to-low signal transition triggers timer 121.

During the running of timer 121, a signal is communicated via lead 128 to the first positive action response element (not shown) previously described as the deterrent action such as turning on porch lights, radios, etc. Also, timer 121 is communicated via lead 129 to the third terminal of NAND gate 117. Thus, NAND gate 117 is now two-thirds activated by the combination of the output of timer 121 and the output of timer 119. Should a third sensor A through E be tripped in addition to the previously tripped two sensors, this will generate an output through NOR gate 114 and NOR gate 115, thereby providing the third needed input to NAND gate 117 and a pulse through timer 130. This timer serves a purpose similar to timer 126 previously discussed of delaying the pulse from NAND gate 117 by approximately 1 millisecond before triggering timer 122. The low pulse from NOR gate 114 also triggers timer 118. As previously mentioned, timer 118 activates the timer recycle driver transistors 143, 144, 145 and 146 which discharges timer capacitors 150, 151, 152 and 153 thereby resetting the corresponding timers to zero. Hence, timer 119 and timer 121 accumulated time periods are reset to zero and they re-initiate their timing cycle. The output signal from timer 130 triggers timer 122 which begins its timing cycle. A high output signal is present at line 132. The high signal level represents the second level of active response and is one of the aforementioned described deterrent responses. In addition to activating the second stage active response, the high signal from timer 122 to NAND gate 134 provides the second of three required inputs to this element. The first such signal is provided by the alerting of the system via timer 119. The third input required by NAND gate 134 is supplied by activation of a fourth sensor A through E in addition to the three previously activated sensors. As previously described, the activation of the fourth sensor is communicated through NOR gates 114 and 115 to the third input terminal of NAND gate 134 thereby activating the fourth stage timer 123 and initiating the third level response at line 135. Concurrent with the activation of the third terminal of NAND gate 134, the signal from NOR gate 114 also triggers timer 118.

As previously discussed, the output signal of timer 118 activates the timer recycle driver transistors 143, 144, 145 and 146 which discharge timing capacitors 150, 151, 152 and 153 thereby resetting the corresponding timers to zero. Thereafter, timers accumulated time periods in timers 119, 121 and 122 are reset to zero and they restart their timing cycles. The third level response may be any active response desired by the owner or occupier of the premises such as external alarms, internal alarms, automatic telephone dialers, etc. This alarm response will continue for as long as the time period previously set into the timer by means of adjustable resistance.

Automatic reset of the system occurs when timer 119 times out and its output signal at junction 124 changes from a high level to a low level. This change in level is transmitted through capacitor 156 to junction 157 which causes a dip in voltage at junction 157. This dip in voltage represents a change from a high signal level to a low signal level and back to a high signal level. It is trans