Intrusion And Fire Detection System

Abstract

A burglary and fire detection system in which sensors detect an intrusion into the space to be protected and transmit signals to logical control circuitry. After the signals from the sensors have been processed by the circuitry an alarm condition is sounded and/or appropriate authorities are notified. The system is set with an exit door in open position, and no alarm is transmitted for as long as the door remains open. An alarm is first transmitted after the door has been closed and then reopened.

Description

BACKGROUND OF THE INVENTION

In the past, systems for the detection of intrusion into premises by burglars were complex in design, difficult to operate, and uneconomical to manufacture. Past systems have been particularly difficult to operate by the owner of the premises or the authorized personnel designated by the owner to enter the premises. In some systems, the owner would be compelled, for example, to trigger the alarm each time he entered the premises. In order to prevent the alarm from sounding too long, he would then be required to rush to a control box into which he would insert a key for the purpose of turning off the alarm. In other cases, the system had provision for allowing the owner a short period of time to turn the key in the control box before the alarm would sound. In such a system however, the owner would be required to rush out of the premises once he set the alarm preparatory to leaving the premises. Systems are also in use in which a control key is mounted directly onto the door and permit the owner to turn on and off the alarm from the outside of the premises. Such design does not require the owner to rush in his actions for operating the alarm, but at the same time, it exposes the control key to the potential burglar who may then tamper with the keylock at his leisure. Furthermore, if a time delay was included in any of the systems to give the owner time for carrying out any one of the operations associated with the alarm system, such a delay would also prevail or be incurred when the burglar were to enter through a window, for example. This delay would then give the burglar an amount of time in which he could disarm the alarm system. Such systems, moreover, do not lend themselves well to fire protection because the time delays incurred could result in severe damage to life and property. Thus, in a fire detection system, it is of the utmost importance that when a fire is once detected, an alarm condition be registered immediately thereafter.

Accordingly, it is an object of the present invention to provide a burglar and fire detection system which will detect an intrusion or a fire within premises to be protected without requiring special skills to operate. It is also an object of the present invention to provide a burglar and fire detection system which will not require hurried actions for setting or turning off the system upon entering or leaving the premises. It is a further object of the present invention to provide a detection system of the aforementioned character which will notify directly police or fire authorities in the event of an intrusion or fire within the premises to be protected.

SUMMARY OF THE INVENTION

A burglary and fire detection system in which sensors are mounted directly on or in the proximity of windows, doors and other openings of the premises to be protected. The sensors when triggered or actuated transmit electrical signals to a control circuit which examines the signals and responds by immediately registering an alarm condition or postponing the alarm condition for a predetermined time interval. The control circuit furthermore, determines from the sensor signals whether a burglar alarm condition or fire alarm condition is to be registered. The control circuitry is in the form of interconnected relays or digital transistor circuits performing the logical functions required by the control circuitry in carrying out its designated task. The output signals from the control circuitry are transmitted directly to a central station or police and fire stations. If the signals are transmitted to a central station, monitoring personnel at this location may, in turn, notify police or fire authorities, as well as dispatch investigating personnel.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an isometric view of the space to be protected through the burglar and fire detection arrangement of the present invention;

FIG. 2 is a functional block diagram of the arrangement for protecting the premises in FIG. 1, and shows the control circuitry for processing the signals derived from the sensors;

FIg. 3 is an electrical circuit diagram, in the deenergized state, of one embodiment of the circuitry used in FIG. 2 for processing the sensor signals and exercising the controlling functions;

FIG. 4 is a logical diagram of the embodiment of FIG. 3, and provides for the substitution of electronic gates for electromechanical relays.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawing, and in particular to FIG. 1, sensors are mounted directly onto the windows, doors and other openings through which the premises to be protected may be penetrated. Thus, in a typical premises 10 to be protected, a window 12 has mounted onto it sensors 14 and 16. These sensors detect when the movable window frame is displaced so that the window becomes open after having previously been shut. These sensors 14 and 16 will detect the opening of a sash window, for example, through movement of its upper or lower sections. The sensors 14, for example, will detect downward movement of the upper section 12a, whereas the sensor 16 will detect upward movement of the lower section 12b of the sash window 12. These sensors 14 and 16 may be simple mechanical switches with parts mounted on the movable and/or stationary frames of the window which become opened or closed depending upon the position of the window. Such mechanical switches are well known in the art and will therefore not be described further here. The sensors 14 and 16 may, on the other hand, also be in the form of magnetic switches with parts mounted on the movable and stationary frames of the window. These magnetic switches are designed so that when brought into the proximity of a magnetic field, the switch becomes actuated to either open or close a circuit. For practical application, a permanent magnet may, for example, be mounted on the movable frame and the switch itself be mounted on the fixed frame. The mounting is such that when the window is closed, the permanent magnet lies directly in proximity of the magnetic-sensitive switch. Accordingly, when the window becomes opened and the permanent magnet is thereby moved out of proximity of the switch on the stationary frame, the switch transfers state and transmits a signal designating the opening of window through either opening or closing a circuit. Such magnetic-sensitive switches are also well known in the art and therefore require no further description. A photoelectric sensor can also be provided to detect intrusion through the window. In such an arrangement a light source on one side of window, for example, directs a light beam against a photosensitive element located at the opposite side of the window. When this light beam becomes interrupted during an intrusion, a signal is transmitted from the photosensitive element and interpreted to designate that the window has been opened. Photoelectric sensors of this character are also very well known in practice and will therefore not be further described. In conjunction with the sensors 14 and 16 which detect positional changes in the movable frames of the window, silver foil 18 may be applied directly to the window glass 20 to detect when the glass has been fractured. Such conductive silver foil is in conventional use and accordingly requires no further explanation here. It is thus seen, that through the switches 14 and 16, and the conductive foil 20, the window 12 may be entirely protected against intrusion.

The door 22 of the premises 10 to be protected may be similarly guarded against intrusion. A sensor 24 similar in construction to the sensors 14 or 16 may be mounted with parts on the door and/or the door frame. Thus, if a magnetic switch as described above for the sensors 14 and 16 is selected, the permanent magnet is mounted onto the door, whereas the magnetic-sensitive switch is mounted onto the door frame and directly in proximity of the permanent magnet when the door is closed. If, in this arrangement, the door becomes opened, a permanent magnet is moved out of proximity of the magnetic-sensitive switch and a signal is transmitted, thereby, by the switch to designate that the door has been opened. This same arrangement used for the door 22 can also be used for the window 12 if the latter is a casement type of window rather than a sash type. Thus, magnetic switches used for the sensor 14 and 16, for example, may be applied to either sash or casement windows, and only a difference in mounting is involved in adapting these switches to one type of window or another. The sensor 24, furthermore, may be, similar to the sensors 14 and 16, a photoelectric sensor or a simple mechanical sensor as described above.

To protect the premises 10 against intrusion by cutting directly through the door 22 without actually opening the door, a wired panel 22a may be mounted directly within the door or on one of the sides thereof. Such a wired panel may consist of a base panel mounting of electrically insulting material upon which wire or conductive foil is laid upon the panel in weaved or zigzag fashion. If the wire or conductive foil is then cut at any point along its length, a circuit connected to the panel becomes interrupted to designate a possible intrusion through the door proper. A wired panel of this type may also be used on the floor of the premises 10 directly inside of the door 22. In such a case the panel is in the form of a floor mat and cooperating with a conductive member normally held separated or spaced form the wired mat. When an intruder then opens the door 22 and steps onto the mat and the conductive member, a signal is transmitted designating the presence of the intruder. In such an arrangement the mat may be used in place of the sensor 24. Mats of this type are also well known in the art.

To protect against penetration of the premises through the walls, floor or ceilings of the premises, wired panels as described above may also be mounted within the walls or directly on the wall surfaces. Similarly, wired panels may be mounted in this manner within or on the surface of the floors and ceilings. Any opening generated by an intruder through either the walls, floors or ceilings, will then be detected through the wired panels. In lieu of the wired panels vibration sensors 44 may also be mounted directly onto the wall surfaces, floors or ceilings. In such an arrangement any tampering with the walls, for example, will produce mechanical vibrations which will actuate the vibration sensor and thereby transmit a signal designating that the walls are possibly being broken through.

For the purpose of protecting the premises 10 against fire, heat detection sensors 38 may be mounted at various locations within the premises. Such heat sensors may be of the conventional bimetallic strip form in which a circuit through the switch is either opened or closed depending upon the temperature to which the switch is subjected. These heat detection sensors, for example, will open or close a circuit when the temperature exceeds 135.degree. . In conjunction with such heat detectors, smoke detectors 40 may also be used. Such smoke detectors are in conventional use and will transmit a signal when surrounded by smoke. This signal from the smoke detector can then be used to register a fire alarm condition even through no fire has been in contact with the smoke detector housing. Fire detection can also be supplemented through the use of chemical devices 42 which sense conditions of the air or immediate environment that are favorable to combustion. With such chemical devices, therefore, it is possible to detect a fire prior to its actual occurrence. Often referred to as ionization type of fire detectors, they detect the presence of smoke and combustion products in the earliest or incipient stages when gases alone are being produced by the combustion.

In accordance with the present invention, sensors are associated with the window 12, front door 22, side door 26, as well as the walls, floors and ceilings of the premises 10 to be protected. When any of the windows, doors or walls of the premises, for example, are penetrated an alarm condition is immediately registered. This same situation prevails when any one of the fire detection sensors becomes actuated. A different treatment, however, is applied to the front door 22 through which the owner of the premises or other authorized persons enter for the purpose of disarming the alarm and preventing the registering of an alarm condition as a result of the opening of the door 22. Thus, when the door 22 is opened after the system, in accordance with the present invention, has been set for operation, a predetermined time interval is allowed between the instant the door is opened and the instant that the alarm condition is actually registered. This time interval allows the authorized person to shut off or disarm the system after entering the premises. The disarming process may be carried out through the turning of, for example, a key or rotating a coded disc similar to the combination dial locks used in safes. Since an intruder would not possess such a key or the knowledge of the code to be used in conjunction with the code disc, the intruder would not be in a position to disarm the alarm. In the system of the present invention, the alarm cannot be shut off by the intruder once it has been registered or triggered.

The different sensors associated with the windows, doors, walls, ceilings and floors are all connected to a control and switching circuit 28. The latter identifies the origin of the signals as received from the sensors and will transmit an alarm signal 30 immediately upon actuation of any of the sensors other than the sensor 24 for the front door 22. When the sensor 24 associated with the front door 22 becomes actuated, the alarm signal 30 is delayed through a delay circuit 32. Thus, when the signal 34 is applied to the control and switching circuit 28 through the setting key switch or coded disc 36, and the sensor 24 is actuated, the alarm signal 30 passes through the delay circuit 32 and is thereby delayed for a predetermined time interval. The alarm signal in this case, however, is transmitted only when the door is opened a second time. The control circuit 28 notes the condition that when the door 22 is opened for the first time, it is because the authorized persons are leaving the premises, and therefore no alarm signal is transmitted. If an intruder opens the door 22 it will be the second opening for that door since the alarm has been set, and as a result an alarm signal will be transmitted at that time. When, however, any of the window sensors 14, door sensors 27, or vibration sensors 44 associated with the floors, ceilings or walls are actuated, an immediate intrusion can be implied and as a result the alarm signal 30 is transmitted directly from the output terminal 46 of the control circuit 28. In this manner, the alarm signal 30 is registered immediately and without delay. The control circuit 28, in accordance with the present invention, provides also an indicating signal 48 which indicates to the owner or user of this system that all sensors are in their proper operating state, and that all windows and doors are closed, as required, prior to leaving the premises. This indicating signal 48 may be transmitted, for example, to an indicating lamp which, after the setting unit 36 has been actuated, notifies the user or owner that he may leave the premises with the knowledge that after he closes the door 22 behind him, the premises will be secure against intrusion and/or fire. With regard to the fire detection feature of the present invention, the alarm signal 30 will be derived from the terminal 46 immediately after the temperature sensors 38, smoke sensors 40, or chemical sensors 42 have been actuated. Thus, the control and switching circuit 28 performs several logical functions which transmit the alarm signal 30 through either the delay 32 or the terminal 46, depending upon the states of the various intrusion or fire sensors. In addition, the circuit 28 provides an indicating signal 48 which guides the user of the protective system in determining that all sensors in the system have been properly set prior to leaving the premises.

The detailed design and structure of the control and switching circuit 28 is shown in an exemplary embodiment of FIG. 3, which is shown in the deenergized state. The key switch 36 which may be used to either set or turn off the detection system, is a single pole, single throw key switch. Thus, this switch may be operated through a simple turn of a conventional key, and is commercially available. The sensor 24 associated with the front or main door 22 is in the form of a single pole, double throw magnetic switch which is magnetically actuated in a manner described above in relation to magnetic switches. All of the window switches 14 and 16, the conductive foil 18, and additional door sensors 27 are all connected in series to the coil of a relay 50. All heat detection sensors 38, smoke sensor 40 and chemical devices 42, are moreover also connected in the series circuit leading to the coil of the relay 50. The arrangement of FIG. 3 is designed and adapted to conform to a closed-circuit system in which monitoring current continuously flows through the sensing devices.

When the key switch 36 is turned so as to set the system, and all windows and doors are shut with the exception of the front or main door, the coil of the relay 50 is energized. If the front or main door through which the owner is to leave the premises remains, furthermore, in the open position when the key switch 36 is closed, the relay 52 becomes energized. This results from the condition that the magnetic switch 24 on the front or main door forms a closed circuit between the coil of the relay 52 and the voltage source 54. When the relay 52 is thus energized, the indicating lamp 56 is energized through the voltage signal 48 arising from the condition that both relays 50 and 52 are energized simultaneously. Thus, the indicating signal 48 arises, as noted above, only when all windows and doors, except the front door, are closed and all sensors are in their operative states. The indicating signal 48 and indicating lamp 56 energized by this signal thereby provide the owner or user of the system with an indication that when he closes the front door behind him the premises will be protected. Once the owner does leave through the front door 22 and the latter becomes closed, the relay 52 becomes released as the magnetic switch 24 transfers positions. When the movable contact of the switch 24 reaches the position shown in the drawing, the relay 52 has been released or deenergized and the relay 58 becomes energized. At the same time, the indicating lamp 56 no longer lights since the relay 52 has become deenergized. This is a desirable feature which extends the operating life of the indicating lamp 56, since there is no need for maintaining this lamp lighted within the premises after the latter have become fully secured, and the owner has left. If now, any of the series-connected sensors on the windows or doors, for example, are opened, the relay 50 becomes deenergized and a closed circuit is formed by the pole 50a between the junction point or circuit point 30 and the terminal 36a at the output of the key switch. Since the latter is in closed or set position, a voltage appears at the circuit point 30 and is available for registering an alarm condition. This alarm condition, therefore, appears immediately upon interruption of the monitoring current through actuation of any one of the sensors from its normal operating state. This condition also applies to the fire sensors 38, 40, 42 which are connected in closed series circuit with the door and window sensors. It is also often to advantage to install panic buttons or switches 39 which may be hand or foot actuated to transmit an alarm. Thus, if a pushbutton 39 is installed at the bedside of a person within the premises to be protected such person can immediately transmit an alarm signal by depressing the pushbutton in the event of a fire or burglary. At the same time, the switches 39 can be in the form of foot-operated switches distributed throughout the premises and connected in series to be operated when an emergency condition arises.

Consequently in the absence of an intrusion or fire, the relays 50 and 58 are energized and no alarm signal appears at the circuit point 30. The relay 58 has its coil connected directly to the pole 58b which leads, through its stationary contact, to the terminal or circuit point 36a. As a result, the relay coil 58 remains energized once it has a current pulse applied to it. Accordingly, when the owner returns to open the premises and the magnetic switch is transferred to the position opposite to that shown in the drawing, the coil of the relay 58 remains energized through the contact 58b. At the same time, the relay 52 becomes energized since the door 22 has become opened and the switch 24 has correspondingly changed state. With the relays 52 and 48 both energized simultaneously, a voltage signal is transmitted from circuit point 36a, through the closed contacts 58b and 52b, and applied to the time delay circuit 32. It is to be noted that once the relay 52 is energized upon reentering the premises through the front door, it remains energized even if the front door were to be again closed. This condition results from the interconnection of the pole or movable contact 52a with the moveable contact 58a leading to the circuit point 36a. Thus, as a result of the relay 58 being in the energized state, the coil of the relay 52 is fed with current through the circuit of the two contacts 52a and 58a and the relay 52 thereby continues to remain energized regardless of the position of the switch 24. To prevent the registering of an alarm condition due to the resulting voltage applied at the terminal 32a, it is necessary to interrupt the circuit by turning the key switch 36, before the expiration of the time interval determined by the time delay 32. If the key switch is not opened before this time interval, an alarm signal 30 appears.

The alarm signal 30 may be applied directly to an alarm device such as bells 60, a siren 62, or horn 64. Such audible alarm devices serve to scare the intruder and induce him to leave the premises without delay. While the use of such alarm devices aid in preventing a burglary from being fully carried out after the burglar has intruded the protected premises, they do not function to aid in catching the burglar. Thus, after the burglar hears the alarm sounds, he may leave the premises so rapidly that police authorities may not arrive in time to intercept him, provided such police authorities have been summoned by someone who has heard the alarm.

For the purpose of notifying police authorities at the earliest opportunity after an intrusion has occurred, it is desirable to transmit the alarm signal 30 directly to the police station 66 serving the premises. Such transmission of the alarm signal 30 to a remotely located police station may be accomplished over telephone lines which may, for example, be leased from the local telephone company. At the same time, auxiliary telephone transmission apparatus 68 may be used to avoid the requirement of using a separate and independent telephone line between the premises to be protected and the police station. Such an auxiliary transmission device 68 may be in the form of, for example, a conventional telephone dialing unit which, upon being actuated by the alarm signal 30, dials the telephone number of the police station and then transmits a recorded message giving the location of the premises in conjunction with the statement that an intrusion has occurred into the premises. Such auxiliary transmission devices 68 are well known in the art and will therefore not be described here further. If the system is selected in which the alarm signal 30 is transmitted directly to the police station, it may be desired to disconnect the audio-alarm device 60, 62 and 64 for the purpose of realizing a silent alarm so that the intruder is not informed that the police authorities have been notified of the intrusion. Such a system arrangement is desirable when the owner leaves the premises vacant behind him. When, however, the owner is within the premises and wishes that the burglary and fire detection system, of the present invention, be fully operative while the owner is asleep during the night, for example, it may be desirably to have the alarm signal 30 transmitted to the police station and, at the same time, to the audio-alarm devices. In this manner, protection of the persons within the premises is obtained at the expense of not catching the intruder. Thus, when the intruder hears that such an alarm has been registered, it is likely that he will try to escape by leaving the premises without delay, and thereby have not sufficient time available to do bodily harm to the inhabitants of the premises.

To permit selected connecting and disconnecting of the audio devices, as well as the police station to and from the alarm signal 30, independent selector switches 70 are provided. These selector switches may be independently and separately actuated to permit any desired combination of connections between the alarm signal 30 and the audio-alarm devices as well as the police station. In addition to the audio-alarm devices 60, 62 and 64, it may also be desirable to apply the alarm signal 30 to visual-alarm devices such as a flashing red light 72, a steady red light 74, flood lights 76, and a television tape recorder 78. The flashing light 72 may be mounted directly at a window of the premises for the purpose of informing neighbors and bypassers to summon authorities to investigate the premises. The steady light 74, on the other hand, may be used in the same or another window to indicate to the owner that the alarm has been triggered from within for whatever reason. Thus, after the owner has set the alarm and closed the front exit door behind him, he may wish to be assured that the alarm was not triggered during the process of closing the door. By glancing afterward toward the window in which the steady lamp 74 is located, he may be reassured that the alarm was not triggered if no such steady light signal appears. Such a steady light may be used in conjunction with the silent alarm to the police station, since such a steady light signal is not likely to scare off the intruder, while the premises are vacant and in the absence of audio-alarm devices. Flood lights 76, however, may be used in conjunction with such audio-alarm devices mentioned above, to further scare the intruder, if this particular function is desired. If, for example, it is intended to have the intruder leave as rapidly as one would wish, it is likely that the sudden appearance of flood lights in addition to the sounding of the audio-alarm devices will contribute much to this desired result.

The alarm signal 30 may be also transmitted to a television camera which may or may not operate in conjunction with a television tape recorder. When using such a television system 78, the intruder may by visually observed from the moment that the camera is switched to its operative state, if a remotely located television receiver is used for the purpose of monitoring the premises. To avoid the necessity of continuously monitoring the premises with a television receiver over closed circuit, for example, a television tape recording unit may be used in conjunction with the television camera. Such a television tape recording unit will record the scene observed by the camera and thereby provide a permanent record for subsequent playback. Such an arrangement may be desirable in subsequent court trails, for example, arising out of the intrusion. Since such television equipment is usually costly, a photographic or motion picture camera 80 may be employed in its place. The camera 80 would be triggered by the alarm signal 30 in a manner similar to the television system, and upon such actuation by the alarm signal 30, the photographic camera may be arranged to take a picture or a plurality of pictures of the premises and thereby also of the intruder. To further record the circumstances of any intrusion, the alarm signal 30 may also be applied to an audio recorder 82 which may be in the form of a magnetic tape recorder, a disc record, a wire recorder, or one of the conventional sound recording devices. By actuating the proper ones of these selector switches 70, it is possible to connect, disconnect and combine any number of the preceding visual and audio devices.

In lieu of transmitting the alarm signal 30 directly to the police station 66, it may be of advantage in particular instances, to transmit this alarm signal to a central monitoring station 84 prior to notifying the police. Thus, in a densely populated area, for example, it may not be practical to have a large number of protected premises communicate directly with the police. In such a case, a central monitoring station 84 may serve as an intermediary between the protected premises and the police. Such an arrangement, permits any number of premises to be protected, while requiring only a single line of communication between the central station and the police. The central monitoring station 84 also affords the opportunity of investigating any alarm so that the police will not be notified in the event that a false alarm has occurred. When many premises to be protected are, furthermore, closely located such as in a large apartment house, and the police station is relatively distantly located from such premises, the central monitoring station 84, may be used to reduce the total length of communication lines that would ordinarily be required between the police and the premises in the absence of the central station 84. The latter can also serve directly as a source of armed guards which are dispatched with or without police authorities. The alarm signal 30 may be used to actuate either an open circuit or a closed circuit communicating with the police.

In particular installations it may be desired to provide a fire alarm system independent of the burglar alarm system. In such an independent fire alarm system, a fire alarm signal can be transmitted directly to the fire station, instead of communicating such a signal via the police. Such a system results in earlier notification of the fire department and thereby diminishes the potential damage to the protected premises. If a closed-circuit fire alarm system is to be independently installed for this purpose, the coil of a relay 86 becomes energized directly from the voltage source 54 through closed-circuit contacts 14a, 16a and 18a which are identical to the contacts 14, 16 and 18, respectively, described above for the use of fire detection. Provided that the pole or movable contact 86a of the relay 86 is in the position shown in the drawing, the fire detection system has been actuated through the opening of any of the contacts associated with the fire detection sensors, resulting in the deenergizing of the relay 86. In this state of the relay 86, therefore, a fire alarm signal 88 is transmitted from the pole or contact 86a. This alarm signal 88 may be transmitted directly to the fire department and independently of the police station. If, on the other hand, the fire detection sensors has not been actuated, the relay 86 remains energized and the signal 88 is inhibited from being transmitted to the fire department. By connecting the independent fire alarm circuit 85 directly to the voltage source 54, the fire detection circuit may be operative at all times, even when the burglar detection system is inoperative or has been turned off. The fire detection system 90 is the open-circuit equivalent of the fire detection circuit 85. Thus, if an open-circuit system is to be used, open-circuit contacts 38b, 40b and 42b may be connected in parallel to transmit the fire alarm signal 92. The circuit contacts 38b, 40b 42b are associated with the fire detection sensors and become closed when their respective sensors become actuated. In this manner, these contacts 38b, 40b and 42b serve the same function as the contacts 38a, 40a and 40b with the only exception that the latter are closed-circuit contacts whereas the former are open-circuit contacts.

The voltage source 54 may be advantageously constructed by providing a transformer 100 which steps down the utility supplied voltage of 110 volts, for example, to 6 volts suitable for transmitting power without requiring special protective power transmission lines. Through the use of a rectifier circuit 102 which may be of the conventional full-wave type, the 6 volts AC are converted to 6 volts DC and applied to a fixed contact of a relay 104 which is energized directly by the 110-volt line. The movable contact 104a leads directly to the circuit point 54a, and will provide operating voltage derived from the transformer 100. In the event that a power failure occurs and the utility voltage is not available, the relay 104 becomes deenergized so that the movable contact 104a transfers to the position in which it becomes connected to the battery supply 106. Thus, this battery serves as a standby source of power which allows the burglar and fire detection system to remain operative even under conditions of utility power failure, or the severance of power lines by intruders or fire.

The control circuit 28 may be synthesized through electronic logical elements rather than electromechanically operating relays. An advantage of using electronic circuitry rather than relays resides in the feature that the electronic circuitry may thereby be confined to a particularly small space. Thus, control circuit 28 shown in detail of FIG. 3 with the use of relays, has the logical diagram shown in FIG. 4. For example, the logical conditions to be satisfied by the circuitry of FIG. 3 is such that a signal output is applied to the input 32a of the time delay 32, when and only when the door associated with the switch 24 has been opened after having been previously closed. Accordingly, a logical AND-gate 200 is required to perform this logical function. One input to the AND gate is connected to the fixed terminal 24b of the switch 24, whereas the other input to the gate 200 is connected to the terminal 24a of this switch. When the premises have been once secured by the owner, and the front door has been closed, a signal input will be applied to the AND-gate 200 from the terminal 24b. When returning, now, to reopen the door, the switch 24 transfers positions and a signal is applied to the AND-gate 200 from the terminal 24a. By means of the capacitor 202 a storage device is realized for remembering that the door had been previously closed. Thus, the input of the gate 200 leading to the contact 24b will be retained, for a period of time, even though switch 24 transfers positions. With the two inputs both simultaneously in the "on" state, a signal appears at the output of the gate 200 and is transmitted to the time delay 32. The latter is of the bistable type so that once actuated by a pulse from the output 32a of the gate 200, it will remain in the actuated state. Therefore, once actuated in this manner, the time delay 32 will transmit a signal 30 for registering an alarm after a predetermined time interval designed to give the owner sufficient time to disconnect or disarm the burglary detection system. Another condition which is to be met by the circuitry of FIG. 3, is that the indicating lamp 56 is to be turned on provided a signal is transmitted from the contact 24a, while a signal appears simultaneously at the circuit point 50c. This function is performed through the AND-gate 204 which has one input leading to the contact 24a, and another input leading to the series connected contact for windows, doors, and fire detectors, which terminate in the circuit point 50c. It is also a condition of the circuitry of FIG. 3 to register an alarm immediately, without delay, when the signal prevailing at circuit point 50c is interrupted, after the front door had been closed for leaving the premises in secured condition. This feature is realized through the AND-gate 206 which has one input leading to the contact 24b, and another input leading to the circuit point 50c by way of inverter 208. The latter inverter is required since a signal input to the gate 206 is desired when no signal appears at the circuit point 50c. It is not necessary to include the connection between the circuit point 36a and any of the AND gates, since an AND function is realized through the series connection of the switch 36 and the switch 24. Thus, no signal outputs may be realized from the contact 24a and 24b if the switch 36 is not closed. The logical gates and inverter in FIG. 4 are of the conventional type known in the art. The arrangement of FIG. 3 may also be used to guard against the spoilage of food in a freezer powered from the same 110-volt supply which maintains relay 104 energized. A signal device 150 in the form of a lamp or buzzer, for example, may be used to report that the 110-volt power is inoperative. Thus when the relay 104 becomes deenergized, contact 104b connects the signal device 150 to the battery 106. This feature is particularly useful in protecting contents of freezers, and avoiding damages incurred from equipment which depends on the continuous operation of the 110-volt power.

Claims

I claim:

1. A method for arming an intrusion detection system and transmitting an alarm upon an intrusion into an enclosed space, comprising the steps of: opening said enclosed space a first time; activating said system and setting said system to a first state while said space is open; inhibiting transmission of said alarm indefinitely while said enclosed space is open for the first time from the instant that said system is in said first state; closing said space and setting said system to a second state, said system being armed while in said second state; opening said space a second time and setting said system to a third state; and transmitting said alarm signal a predetermined time interval subsequent to said second opening of said space while said system is in said third state.

2. An arrangement for detecting intrusion into a predetermined enclosed space comprising, in combination, at least one opening into said space; closure means for covering said opening; which means in proximity of said opening and providing a first signal when said opening is uncovered and a second signal when the opening is closed; signal-processing means linked with said switch means and having: first circuit means actuated by said first signal when said opening is first uncovered, second circuit means actuated by said second signal when said opening is covered after said first uncovering, third circuit means connected to said first circuit means and said second circuit means and actuated by said first signal when said opening is uncovered a second time thereafter, and fourth circuit means connected to said third circuit means for emitting a third signal a predetermined time interval subsequent to said second uncovering of said opening, said signal-processing means inhibiting transmission of said third signal independent of time from the instant that said first circuit means is actuated by said first signal to the instant that said second circuit means is actuated by said second signal upon closing said opening after said first uncovering, said opening being uncovered during the interval between said instant that said first circuit means is actuated by said first signal and said instant that said second circuit means is actuated by said second signal.

3. The arrangement as defined in claim 2 including fire-sensing means within said space for sensing the rise and presence of a fire within said space; and means within said signal-processing means and connected to said fire-sensing means for emitting a signal immediately upon actuation of said fire-sensing means.

4. The arrangement as defined in claim 2 including setting means operatively connected to said signal-processing means for setting said signal-processing means into operative state prior to covering said opening.

5. The arrangement as defined in claim 2 including at least one additional opening with means for covering the same; sensing means cooperating with said additional opening for sensing when said additional opening is uncovered and covered by the covering means for said additional opening; and means in said signal-processing means for emitting a signal immediately upon uncovering of said additional opening.

6. The arrangement as defined in claim 2 including indicating means operatively linked to said switch means for indicating the operative state and said switch means.

7. The arrangement as defined in claim 2 including auxiliary sensing means for sensing penetration into said space with said opening remaining covered.

8. The arrangement as defined in claim 2 including sound emitting means operatively connected to said signal-processing means and actuated by said third signal.

9. The arrangement as defined in claim 2 including picture recording means for recording the visual appearance of the interior of said space.

10. The arrangement as defined in claim 2 including visual indicating means operatively connected to said signal processing means and actuated by said third signal.

11. The arrangement as defined in claim 2 including signal-transmitting means connected to said third signal-processing means for transmitting said third signal to a location remote from said space.

12. The arrangement as defined in claim 2 including manually operable switching means within said space and linked to said signal-processing means, said signal-processing means emitting an undelayed signal when said switching means is manually actuated.