GB1604837A - Intruder detector - Google Patents

Description

(54) INTRUDER DETECTOR (71) We, MASTIFF SECURITY SYSTEMS LIMITED, a Company registered under the Laws of England, of Randalls Road, Leatherhead, Surrey, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an intruder detector and is a development of the inventions described in British Patents Nos.

1414119, 1414120, and 1528901. Those systems involved tokens for being carried by authorised persons in a security area for enabling them to open doors only when carrying an appropriate token. That system did not detect whether an intruder was present, but merely prevented him from opening the door, and an object of the pre sent invention is to provide a modification of that kind of system according to which the presence of an intruder can be detected.

An intruder is defined as someone going through a door in either direction without possessing means for generating the appropriate radio signal.

According to the present invention there is provided a door frame and an intruder detector whose operation is initiated by someone opening a door in the frame, the detector comprising means for generating an entry signal when someone passes through the door frame, means for picking up signals generated by a token carried by an authorised person in the region of the frame, and a control unit arranged to detect an entry signal and to take alarm action, and means arranged to inihibit the alarm action if signals from a token are being picked up.

It is considered important not ta give an alarm signal if an intruder merely arrives at the door without trying to get through it, because that would lead to many annoying false alarms, and accordingiy an alarm will only be given when the entry signal is generated from someone actually passing through the door frame, for example in response to the breaking of a light beam extending across the door frame from a lamp and photo-electric cell arrangement with the cell connected to the control unit.

The alarm signal must not be generated by breaking the light beam inadvertently when the door is closed and to prevent this a contact can be fitted to the door such that the alarm circuit is inhibited whilst the door is closed.

Once the control unit has detected that there is an intruder, it may be arranged to give an audible warning to frighten the ini truder away, or to lock one or more inner doors opening from the area into which the said door opens, or to give a signal in a control roof, so that appropriate action can be taken to apprehend the intruder or at least to prevent his further progress.

Tn some circumstances it is desired that an unauthorised person not carrying a token can leave the secured premises through the door without giving the alarm. There may then be means operated by such a person, for example, switch contacts on the handle on the inside of the door, arranged to give a signal to replace the signal which will be lost when the door is opened and in that way the alarm system will not be set. Then there can be means such as à pressure mat responsive to the unauthorised person leaving from the outside of the door for resetting the system to be ready to detect an in trusion taking place before the door has relatched. Door closure would also reset the system ready to detect intrusion when the door is next opened.

The invention may be carried into practice in various ways, and certain embodiments will now be briefly described by way of example, with reference to the accompanying drawings: in which FIGURE I is a diagram of a door for detecting an intruder; FIGURE 2 is a sketch showing haw an area into which the door of FIGURE I opens can be controlled against the iF truder; FIGURE 3 is a circuit diagram showing how door handle contacts can be connected in circuit with an indicating lamp and a door latch release relay; FIGURE 4 shows an alternative arrangement to FIGURE 1 which does not give an alarm when someone is leaving secured premises;; FIGURE 5 is a circuit diagram showing how the signals from the arrangements of FIGURES 1--4 can be connected to an alarm device; and FIGURE 6 is a sketch of a door handle switch.

An intruder is defined as anyone passing through the door in either direction without a transmitter transmitting a radio signal with particular characteristics which can be recognised by a control unit.

As shown in FIGURE 1, the door is fitted with three devices each capable of giving an input signal to the control unit.

Thus there is an inductive pick-up loop 11 which is conveniently embedded in the floor, embracing the door opening and a part of the area on either side of the door which door is indicated 12. Then there is a door open/closed sensor consisting of electrical contacts 13 in the door frame, or in the door handle, or one on the door frame and one on the door, which are operated by the opening of the door 12. Finally there is a lamp and photo-electric cell arrangement indicated generally at 14 with the lamp on one side of the doorway, and the photoelectric cell on the other side, normally responsive to a beam of light 15 from the lamp, which beam must be interrupted by any one going through the doorway so that there will be a break in the output from the photo-electric cell, which break constitutes a third input signal to the control unit.

The lamp and photo-cell could be on the same side of the door, if there is a mirror on the other side, or reflection from a person's body is used.

Operation of the control unit is initiated by a signal from 13 when the door is opened.

The control unit is arranged to produce an alarm output if the beam 15 is broken after a half second interval from the opening of the door, and if no correct radio signal is received from the pick-up coil 11 at the time when the signal is received from the beam interruption sensor.

It is clear that if the control unit recognises after the opening of the door that the beam has been interrupted, and the radio signal is present, entry has been made by someone authorised, and not by an intruder and no alarm is given. Since there is a possibility of variation in the strength of reception of radio signal (because of antenna or building design problem), the alarm remains suppressed for half a second after the radio signal ceases to be detected. Equally if the beam 15 is not interrupted, no one has entered through the doorway, and again no alarm is given. If on the other hand the beam is interrupted, and the appropriate radio signal is not received, then the presence of an intruder is established and the alarm signal is generated by the control unit.

In some circumstances that may merely give a visual or audible indication in a control room, so that the authorities can take appropriate action, but in the preferred arrangement of FIGURE 2, where the door 12 controls access to an ante-chamber 17 from which various doors permit access to secured areas, the alarm signal can be arranged to lock closed all the doors indicated at 18, 19, 20 and 21, so that the intruder can get no further. The doors 18, 19, 20 and 21 may be interlocked with doors 12 so that at no time may the door 12 be open as well as any of doors 18, 19, 20 and 21. Preferably however, the doors 18, 19, 20 and 21 are normally released, but are locked automatically when an alarm signal is given from the control unit.

Often there is no desire to catch an intruder but merely to get him to go away and accordingly the alarm signal may also be arranged to operate a warning bell or horn 22 in the ante-chamber 17, so that the intruder will be warned or alarmed and can merely return the way he came through the door 12.

Any of the inner doors 18-21 can have a spy glass so that someone inside one of the secured areas can see if the intruder has left, and if it is safe to open one of the inner doors.

There may be a visual display, either in the ante-chamber 17 or in any of the secured areas that there is an intruder, or that the door should be checked, and inside any of the secured doors there could be a red light indicating the those doors are locked in response to the arrival of an intruder. Then when it is observed through the spy glass that the intruder is no longer there, there may be means inside the secured areas for releasing the locks and resetting the system.

A preferred feature is a lamp 16 in the wall outside the door 12, which is illuminated as soon as a token generating the appropriate radio signals comes within range of the pick-up loop 11 to indicate that the system is ready for release. Although that is a convenience, it is also a source of tampering with the system in that the lamp bulb could be removed from the outside, and a releasing electrical signal could be connected to the lamp terminals, and in order to prevent that, there is included in the lamp circuit a light fuse 26 (FIGURE 3) of perhaps 60 milliamps which can pass lamp current, but would blow in response to a fed-in signal strong enough to release the system.

In the example described above, it may be desirable to release the lock on the door 12 only when an authorised person carrying a token is intending entry. In such a case, a door handle with contacts 23 is fitted to the outside of door 12 and arranged as shown in FIGURE 3 to supply a signal to a door lock release relay 27 and lamp 16 via spring contacts 29 in the door and door post (FIGURE 1) when the handle is depressed by an intending entrant. The circuit includes normally open contacts 28 which are automatically closed when an authorised token is present and is bemg picked up at 11. Thus only when the handle 23 is depressed by a person carrying a token will the lock in the door 12 release, permitting opening of the door.

In the example described above, it may be desirable for the intrusion alarm to be activated only by unauthorised people entering the door 12 from the outside and not by unauthorised people (i.e. those without tokens) leaving through the door 12. The general layout of such an arrangement is shown in FIGURE 4. A sensor to indicate the intending passage of someone leaving door 12 (such as an inner door handle contact 24) would trigger a circuit when the handle is operated to inhibit the operation of the intrusion alarm.

The inhibition would last until the door closed, or a presence sensor such as a pressure mat 25 or photo-electric beam 15 situated outside door 12 indicated that the person had left.

As soon as any person had left the area of door 12, the system would again be operative to detect an intruder who passed through door 12 from outside without a token. A circuit could be constructed as shown in FIGURE 5 to achieve this feature.

Thus output signals from the loop 11 in response to a correct token signal being received, and from the photoelectric cell 14 in response to the light beam not being interrupted are connected to the inputs to a NOR gate which is arranged to give an alarm only if there is a signal from neither of the units 11 and 14. Even so, an alarm can still be inhibited if a signal is applied to the inhibit unit from the Ov side of the relay circuit in the lower half of FIGURE 5.

As long as the door remains closed, the normally closed contact 13 maintains the winding of the relay RL1 energised so that its contact 1/1 is closed and an alarm is inhibited. Opening of the contacts 13 when the door opens releases the contact of relay RL1, and enables an alarm to be given if there is no signal from a token, and if the photocell beam is broken.

If however, as described above, it is desired that an unauthorised person can leave the secured areas without setting off the alarm, the door handle contacts 24 on the inside of the door will be closed as he operates the handle and that will energise the relay RL2 so that its contacts 2/1 and 2/2 will be closed. The closing of the contact 2/1 has the same effect as the closing of the contacts 1/1 which is to inhibit an alarm. The closing of the contacts 2/2 puts an appropriate bias on a transistor in series with the winding RL2, so that the relay remains energised even after the contacts 24 are allowed to open again when the handle is released.As the unauthorised person leaves from the outside of the door, he will operate the normally open switch 21 by a pressure mat or other sensor which will turn off the transistor and allow the relay RL2 to be de-energised so that the contacts 2/1 open again. When the door is reclosed, and the contacts 13 close, an alarm will be inhibited again by way of the contacts 1/1.

In a modification, the initiation signal can be produced by contacts on the door handle as described above at 23 instead of by the contacts 13, and since that signal will be given when the handle is operated rather than when the door is opened, the signal can be led to the door frame through the contacts 29 which are closed while the door is closed.

FIGURE 6 is a sketch of a suitable door handle switch. When the handle is turned, a rotor 31 keyed to it is also turned against a spring 32 and a detent 33 causes an operating member 34 to trip a microswitch 35 containing the controls 23 and 24. The design is simple and reliable.

The invention is applicable to the case where there is an archway at 12 in FIGURE 2, but no door in the archway.

Thus initiation would be in response to the arrival of someone at the door, as detected, for example by a pressure mat or a lamp and photocell, the entry signal would be generated by another lamp and photocell arrangement as described at 14, 15, and the loop 11 would be used as before to detect whether a token was present.

That case is the subject of Application No. 8100262 (Serial No. 1604838) divided from this application.

WHAT WE CLAIM IS:- 1. A door frame and an intruder detector whose operation is initiated by someone opening a door in the frame, the detector comprising means for generating an entry signal when someone passes through the door frame, means for picking up signals generated by a token carried by an authorised person in the region of the frame, and a control unit arranged to detect an entry signal and to take alarm action, and means

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. In the example described above, it may be desirable to release the lock on the door 12 only when an authorised person carrying a token is intending entry. In such a case, a door handle with contacts 23 is fitted to the outside of door 12 and arranged as shown in FIGURE 3 to supply a signal to a door lock release relay 27 and lamp 16 via spring contacts 29 in the door and door post (FIGURE 1) when the handle is depressed by an intending entrant. The circuit includes normally open contacts 28 which are automatically closed when an authorised token is present and is bemg picked up at 11. Thus only when the handle 23 is depressed by a person carrying a token will the lock in the door 12 release, permitting opening of the door. In the example described above, it may be desirable for the intrusion alarm to be activated only by unauthorised people entering the door 12 from the outside and not by unauthorised people (i.e. those without tokens) leaving through the door 12. The general layout of such an arrangement is shown in FIGURE 4. A sensor to indicate the intending passage of someone leaving door 12 (such as an inner door handle contact 24) would trigger a circuit when the handle is operated to inhibit the operation of the intrusion alarm. The inhibition would last until the door closed, or a presence sensor such as a pressure mat 25 or photo-electric beam 15 situated outside door 12 indicated that the person had left. As soon as any person had left the area of door 12, the system would again be operative to detect an intruder who passed through door 12 from outside without a token. A circuit could be constructed as shown in FIGURE 5 to achieve this feature. Thus output signals from the loop 11 in response to a correct token signal being received, and from the photoelectric cell 14 in response to the light beam not being interrupted are connected to the inputs to a NOR gate which is arranged to give an alarm only if there is a signal from neither of the units 11 and 14. Even so, an alarm can still be inhibited if a signal is applied to the inhibit unit from the Ov side of the relay circuit in the lower half of FIGURE 5. As long as the door remains closed, the normally closed contact 13 maintains the winding of the relay RL1 energised so that its contact 1/1 is closed and an alarm is inhibited. Opening of the contacts 13 when the door opens releases the contact of relay RL1, and enables an alarm to be given if there is no signal from a token, and if the photocell beam is broken. If however, as described above, it is desired that an unauthorised person can leave the secured areas without setting off the alarm, the door handle contacts 24 on the inside of the door will be closed as he operates the handle and that will energise the relay RL2 so that its contacts 2/1 and 2/2 will be closed. The closing of the contact 2/1 has the same effect as the closing of the contacts 1/1 which is to inhibit an alarm. The closing of the contacts 2/2 puts an appropriate bias on a transistor in series with the winding RL2, so that the relay remains energised even after the contacts 24 are allowed to open again when the handle is released.As the unauthorised person leaves from the outside of the door, he will operate the normally open switch 21 by a pressure mat or other sensor which will turn off the transistor and allow the relay RL2 to be de-energised so that the contacts 2/1 open again. When the door is reclosed, and the contacts 13 close, an alarm will be inhibited again by way of the contacts 1/1. In a modification, the initiation signal can be produced by contacts on the door handle as described above at 23 instead of by the contacts 13, and since that signal will be given when the handle is operated rather than when the door is opened, the signal can be led to the door frame through the contacts 29 which are closed while the door is closed. FIGURE 6 is a sketch of a suitable door handle switch. When the handle is turned, a rotor 31 keyed to it is also turned against a spring 32 and a detent 33 causes an operating member 34 to trip a microswitch 35 containing the controls 23 and 24. The design is simple and reliable. The invention is applicable to the case where there is an archway at 12 in FIGURE 2, but no door in the archway. Thus initiation would be in response to the arrival of someone at the door, as detected, for example by a pressure mat or a lamp and photocell, the entry signal would be generated by another lamp and photocell arrangement as described at 14, 15, and the loop 11 would be used as before to detect whether a token was present. That case is the subject of Application No. 8100262 (Serial No. 1604838) divided from this application. WHAT WE CLAIM IS:-

1. A door frame and an intruder detector whose operation is initiated by someone opening a door in the frame, the detector comprising means for generating an entry signal when someone passes through the door frame, means for picking up signals generated by a token carried by an authorised person in the region of the frame, and a control unit arranged to detect an entry signal and to take alarm action, and means

arranged to inhibit the alarm action if signals from a token are being picked-up.

2. A detector as claimed in Claim 1 including initiation signal generating mcans comprising contacts on a handle used for opening a door in the frame.

3. A detector as claimed in either of the preceding claims in which the entry signal generating means comprises a lamp and photocell arrangement for establishing a beam which is affected by someone passing the door frame.

4. A detector as claimed in any of the preceding claims in which the signal picking up means comprises an inductive loop encircling the area including the door frame.

5. A detector as claimed in any preceding claim including an audible alarm adjacent the door frame.

6. A detector as claimed in any of the preceding claims in which the alarm action causes one or more inner doors opening from the area into which the said frame opens to be locked.

7. A detector as claimed in any of the preceding claims including switch contacts on a handle on the inside of the door arranged to prevent an alarm being given in response to the door being opened from the inside.

8. A detector as claimed in Claim 7 including means responsive to someone leaving from the outside of the door for resetting the system following operation of the handle from the inside.

9. An intruder detector constructed and arranged substantially as herein specifically described with reference to the accompanying drawings ~ ~ ~