More particularly, the present invention relates to an electromechanical lock system and associated controlling logic that provides a high security barrier system to restrict access through the barrier to authorised personnel only. The system is suitable for domestic or commercial use on fixed premises.

BACKGROUND OF THE INVENTION Various electromechanical locking systems are well-known in the art. Perhaps the best known and most commonly used systems are the various central-locking systems employed in modern cars. Such a system generally comprises a small low-power radio transmitter mounted upon a key-ring or the like. Upon depression of a push-button incorporated into the key-ring the transmitter transmits a low power coded r. f signal, the code of the signal being unique to the particular car. Provided the radio-transmitter is close enough to the car, the coded signal is received by a matching low-power radio receiver in the central locking system. The received code is then compared to a pre-set code for that particular car, and if found to match the central locking system unlocks the car doors by means of the electromechanical locks commonly found in such systems, the constructions of which are well-known in the art. Precise details of the construction of such electromechanical locks or latches are beyond the scope of this specification. It is common in such systems for all of the car doors to be simultaneously unlocked, although it is possible in some systems to preprogram only a specific number of the doors to become unlocked, such as for instance the driver's door only. Whichever configuration is chosen, car central locking systems are characterised by having only a single central controller which controls

all the doors, whether simultaneously or separately. Furthermore, the operation of such systems is generally quite limited. For instance, a characteristic operation would be simply that in an initial state where the doors are locked, activating the coded transmitter will cause the doors to unlock. A second and subsequent activation would then simply cause the doors to lock once more. The system then simply cycles between the two states with each activation of the coded transmitter.

No monitoring of whether the door has been actually opened or if someone has entered the vehicle is undertaken.

With regards to electromechanical locking systems used to secure buildings or other restricted public access areas, various swipe-card/ticket systems are known, a common characteristic being that a key card or ticket must be swiped through or otherwise placed within some form of card reader in order for the barrier to unlock. Such systems have the severe disadvantage that an actual physical operation is required by the user to ensure that the card or ticket is read properly. As will be appreciated by users of various metro systems around the world such as the London Underground, delays can be caused by the need to first find the card/ticket about a user's person and secondly to place the card/ticket in the reader correctly. As such, such systems do not allow for a hands-free operation to unlock the barrier.

There is however, a known"hands-free"system that is employed in some commercial premises that overcomes some of the above-described problems of the common prior art, and which works on the principle of electromagnetic induction. In such a system an authorised user is issued with a"Smart"-card upon which is etched a magnetic circuit. A barrier such as a door which is controlled by the system then has an electromagnetic induction loop placed around it, which generates an electromagnetic field around the door. This field is then carefully monitored.

When an authorised user wishes to enter through the barrier, then they simply approach the barrier, thus passing the Smart-card, which is worn on

their person, through the generated electromagnetic field. The magnetic circuit etched upon the card causes changes in the field as it moves closer to the barrier.

These changes may be detected and used to control the door, allowing the door to be pushed open. Once open, the authorised user together with any companions, whether authorised or not, may pass at will through the door until the door is allowed to fully shut and the lock to re-engage. Once the door is open no provision is made to monitor the passage of persons through the door, nor to ensure that each person passing through is an authorised user. Furthermore the method of detection of the presence of an authorised user by passively detecting such a"Smart-card"is prone to error, and it is not uncommon for users to have to spend many minutes waving their cards in front of the door in order for detection to be achieved.

SUMMARY OF THE INVENTION In contrast to all of the above-described prior art, the electromechanical lock system of the present invention presents a"hands-free" operation which uses the transmission of low-power coded r. f signals to actively signal the barrier to open. Furthermore, each barrier has its own controlling logic resulting in a distributed system with no central control point.

According to the present invention, there is provided an electromechanical lock system providing for remote operation of an electromechanical lock arranged to secure a barrier, comprising: personal portable control means including portable power supply, a personal code generator and a radio transmitter arranged to transmit said personal code on command from a user; and barrier control means including : a radio receiver arranged to receive any transmitted codes; code recognition means for recognition of any received codes; barrier sensing means arranged about said barrier for indicating a present open or closed state of said barrier ; and

control means arranged to control said electromechanical lock dependent upon the sensed state of said barrier and the recognition of the received codes; wherein when said received code is recognised by said code recognition means and said barrier is sensed to be closed then said control means control the electromechanical lock to allow the barrier to open.

The control means may further include a timer element arranged to measure a time period after the barrier has become unlocked. Once the time period has elapsed the control means control the electromechanical lock to secure the barrier closed. The time period should be optimally chosen to try and preclude more than one person traversing the barrier at any one time. The time period may therefore be fixed or variable.

The barrier-sensing means may be any of electrically, mechanically, magnetically or optically driven. That is, any known movement or position sensor can be used as the barrier sensing means, provided that reliable detection of the opening and subsequent closing of the barrier, or of the opened or closed state can be provided.

The system of the present invention presents a distributed system with no central controller. That is, when the system of the present invention is to be employed at more than one barrier, each barrier will have its own local logic and control. More particularly, each barrier will have its own radio receiver, code recognition means, barrier sensing means and control means together with its own electromechanical lock. A particular personal portable control means may be common to and compatible with each local set of other components of each barrier, allowing access through each barrier. A particular personal portable control means will be particular to a single user, however, and each authorised user will have his/her own personal portable controller. Such a system has the advantages that no wiring is required to a single central controller. In addition fault tolerance is built in due to the inherent redundancy in such a system.

Furthermore the issue of the personal portable controllers each with a unique code allows the various fixed sets of each barrier to be programmed to give particular users access to some areas and not to others.

BRIEF DESCRIPTION OF THE DRAWINGS Further features and advantages of the present invention will become apparent from the following description of a number of particularly preferred embodiments thereof, and in particular by reference to the accompanying drawings in which :- Figure 1 shows a first embodiment of the present invention ; Figure 2 shows a schematic block diagram of the important features of a second embodiment of the present invention ; and Figure 3 shows a block diagram of additional features of another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will now be described with reference to Figure 1.

The present invention basically consists of two main parts. A personal portable control means 1 is first provided in which a portable power supply such as a battery 2 provides power to a personal code generation circuit 4 which supplies a personal code to a low-power radio transmitter 6. The radio transmitter 6 transmits the personal code over a channel 8 upon command from an authorised user, for instance by pressing a button on the personal portable control means.

The personal portable control means is to be carried about an authorised user's person, and hence is of relatively small and lightweight construction. Key-ring style hand sets are particularly envisaged, and each authorised user would be issued with a personal set.

The second main element of the present invention is the barrier control unit 3. Each barrier employing the system of the present invention would

have its own barrier control unit 3 conveniently located at or near to the barrier.

The barrier control unit 3 includes a radio receiver 10 arranged to receive and demodulate any signal transmitted over the channel 8. The received and demodulated signal is then fed to a code recognition circuit 12 which attempts to recognise any. code included in the received signal as indicating that the sender of the signal is an authorised user. Code recognition may be by algorithmic or logical means, or alternatively by means of a look-up table contained within the code recognition circuit. Where the received code is recognised as valid a signal is sent to a control means 14 to indicate that the valid code has been received.

The control means 14 also has a second input from a barrier condition sensor 18. The barrier condition sensor is arranged to detect whether or not the barrier is presently open or closed. A signal corresponding to the state of the barrier is then fed to the control means 14.

The control means 14 receives the signals from the barrier condition sensor 18 and the code recognition circuit 12 and applies the two signals to a decision-making circuit to decide whether or not the barrier should be unlocked.

The logical rules governing the decision-making process will be described later.

The control means 14 controls an electromechanical lock 16 on the basis of the output of the decision-making circuit. The electromechanical lock 16 is arranged to allow the lock to secure the barrier closed. The barrier 5 is shown in the drawing as a door, but it is to be understood that any barrier which can be secured to prevent the passage of a person or persons may be used within the system of the present invention. Suitable other barriers may be such as gates, turnstiles or the like. The electromechanical lock may be constructed integral with the barrier or may be externally added to an existing barrier. The only requirement is that it be actuable upon command from the control means 14, and that it is conveniently situated so as to be able to secure the barrier closed.

The barrier condition sensor 18 may be mechanical, electrical, magnetic, or optical in nature, the only requirement being that it is capable of

detecting that the barrier has been opened and that this can be communicated to the control means 14.

Suitable mechanical means would be a simple conveniently placed switch, whereas suitable electrical means could be for example, a mercury-tilt switch. Magnetic means could be for instance a reed switch such as those commonly used in domestic burglar alarm systems. Optical means could be a conveniently placed optical diode responsive to IR or visible light frequencies.

The control means 14 may further include a timing element in addition to the decision-making circuit. The timing element is arranged to be responsive to the signal from the barrier condition sensor 18 and the signal from the code recognition means 12. The purpose of the timer element is to prevent the barrier from being unlocked for too long, in which case unauthorised access through the barrier might occur. The precise operation of the timing element will become clear from a discussion of the logical rules embodied in the decision- making circuit in the control means 14, described next.

The control means 14 controls the electromechanical lock on the basis of a number of logical rules, which take as their inputs the sensed state of the barrier, the known state of the lock, and the output from the code recognition circuitry. The logical rules are based on the following.

When the lock 16 is locked then a signal from the code recognition means 12 that a valid code has been received will cause the control means to control the lock to unlock.

When the lock 16 is unlocked, the receipt from the code recognition means 12 that a further valid code has been received will cause the control means to control the lock to lock.

When the lock 16 is unlocked, then opening the barrier will be detected by the barrier condition sensor 18 which communicates the open state to the control means which controls the lock to lock. This is appropriate where the lock is a latch-type.

When the lock 16 is unlocked, and the barrier is not opened, then the control means controls the lock to lock after a predetermined amount of time as measured by the timing element.

The above logical rules provide for relatively simple but robust operation of the system according to the first embodiment of the present invention.

The timer element in particular helps to ensure that no unauthorised access is made by virtue of automatically re-locking the barrier if no passage is made through the barrier within a predetermined period of time. This prevents the state occurring where the barrier could remain unlocked for a substantial period of time, in which period unauthorised access could occur.

The power supply for the portable control means could be a battery, or alternatively a solar panel, or a combination of the two. Where a combination is used, the battery may be a rechargeable battery arranged to be charged from the solar supply.

The power supply for those fixed elements which are situated at or near to the barrier may be from the domestic mains supply, or alternatively from a battery. Preferably, however, a combination of mains supply with a battery back-up is used. Such a combination allows for emergency battery operation in the event of a power-cut. Where such a combination is used, the battery can further include recharging means to allow the battery to recharge from the mains supply.

A second embodiment including more advanced security features will now be described with reference to Figure 2.

The previously described first embodiment presents the simple case when a sole authorised user approaches the barrier and commands the barrier to unlock using a personal portable control means. Problems can arise however, when more than one authorised user approaches the barrier at once, or where a mix of both authorised and unauthorised personnel desire access through the barrier. Both of these scenarios will be discussed in turn below.

Turning first to the problem of multiple authorised access, the biggest problem facing the system of the present invention is that of contention between users. More precisely, the contention lies between each user's personal portable control means.

Consider the scenario where two authorised users approach the same barrier and each press their handsets at the same time. Two signals will then be transmitted onto the channel 8 at the same time, resulting in interference between the two signals and decreasing the likelihood that a clear signal is received by the receiver 10.

There are several solutions around this problem, any of which may be employed within the present invention.

The simplest is to simply set the transmission frequency of each of the transmitters 6 in each of the portable control means 1 to be different. In this way a FDM radio link can be established which will solve the problem of interference between signals. The disadvantage of this is that the receiver must be made relatively wide band with respect to the received signal, thus decreasing the signal to noise ratio of the received signal which is manifested by a reduced range of the handset. Furthermore, such FDM techniques do not solve the problem of which of the two users actually caused the door to unlock and hence is technically the person allowed to pass through the barrier.

A better solution is to employ time division techniques to resolve contention between users. Various such techniques can be employed, and will be demonstrated with respect to Figure 2. Only those parts essential to understanding have been shown in Figure 2, although it is to be understood that those essential parts of the present invention previously described but not shown are to be implicitly included.

In Figure 2, each of the personal portable control means 1 is further provided with radio receiver 20, which is arranged to receive any signals placed on the channel 8, whether transmitted by the barrier control unit 3, or another

portable control means 1. The barrier control unit 3 is provided with a radio transmitter 22, arranged to transmit onto the channel 8, although such a transmission could be at a different frequency. Such arrangements allow for a variety of methods of defeating the multiple user contention problem.

A first such solution is to simply provide an acknowledgement signal from the control unit 3 onto the channel via the transmitter 22. Such an acknowledgement signal could be simply the first received code retransmitted.

When this is the case, the retransmitted code can be received by all of the handsets and compared to their own codes. The particular handset which then transmitted the accepted code could then indicate acceptance to the user, for instance by suitable indication means such as a vibrator, a flashing light, or an audible alarm.

In order to avoid contention with the transmitted codes from the handsets, the transmitted acknowledgement can be at a different frequency.

Further solutions to avoiding contention can be found by applying various techniques found in the field of contention LANs.

In particular"listen-before-send"and"listen-while-send"techniqu es can be employed.

With the former technique, after the user has commanded the handset to transmit its code, instead of sending the signal immediately, the radio receiver samples the channel to ensure that no other handsets are transmitting. If no other signals are detected then the transmitter 6 is signalled to transmit the code. If, however, the channel is already busy, then the transmitter 6 is prevented or delayed from transmitting the code. Two options are available for delaying transmission of the signal. The first is that the code transmission may be delayed from transmission for the duration of the transmit time of a similar code. In this case, almost immediately after the already transmitting code has finished, the present code can be transmitted. Thus the barrier control unit 3 would receive two codes from different users in quick succession.

A second option is that the handset prevents the code transmission

for the duration of time that it would take for a person to transit the barrier and for the barrier to relock. This then provides an automatic delay which helps prevent more than one person transiting the barrier device at once. Such a system has drawbacks in that there is the statistical potential that a user could always find himself blocked by other users who happen to start their transmissions just before him. In such a case it may take minutes to transit the barrier and hence frustration could result.

With"listen-while-send", after the user has commanded the transmitter to transmit, the receiver monitors the channel to ensure that no other handsets also start transmitting during the duration of its own transmission. If, however, a second transmission and hence contention occurs then the first transmitter is stopped from transmitting, and a delay applied before transmission is attempted again. The delay must have a degree of random back-off to prevent contention between the two handsets from repeatedly occurring.

By combining the"listen-before-send"or"listen-while-send" techniques with automatic acknowledgements as described earlier, then contention between two or more users can be resolved.

The problem of how to prevent more than one person transiting the barrier at once in an unauthorised manner will now be described by way of a third embodiment of the present invention with reference to Figure 3. Figure 3 shows the important elements of the additional features of the third embodiment. The previously described features of any of the first and second embodiments are to be implicitly regarded as being included with the third embodiment.

In Figure 3 there are further provided time integral thresholding means 32, barrier transit detection means 34, and alarm means 36. The time integral thresholding means 32 receive an input from the code recognition means 12 and from the barrier transit detection means 34. The barrier transit detection means 34 are arranged about the barrier and detect the passage of a person or persons through the barrier. The transit detection means could be, for example,

a pressure plate on the floor upon which people transiting the barrier step, or alternatively some form of optical sensor which detects the passage of people through the barrier. It is possible to include the integral thresholding means 32 within the control means 14 in which case the input from the barrier transit detection means 34 would be fed to the control means 14.

The alarm means 36 are controlled by the time integral thresholding means 32 and are used to signal when an unauthorised access has occurred. The alarm means could be a sounder as shown, or alternatively a flashing light or other such attention-grabbing means. Alternatively, a camera or the like could be rigged to take pictures of the people transiting the barrier when an unauthorised access is detected.

The principle of operation is as follows. Assume that a valid code has been received and recognised by the code recognition means 12. The recognition means then output a signal to the control means 14 to unlock the door and also to the time integral thresholding means 32. Within the time integral thresholding means a pre-set threshold value is selected which is an integral value representing the maximum allowable time for a single person to transit the barrier.

The barrier transit detection means begins to provide a signal to the time integral thresholding means 32 once a transit has started to be detected, and for the duration of the barrier transit. This signal is integrated with respect to time and continuously compared to the pre-set threshold value. If the resultant integrated signal exceeds the pre-set threshold then this is an indication that the barrier transit is taking longer than specified, which could be indicative of unauthorised persons attempting to enter immediately behind the authorised person. In this case, when the threshold is exceeded, the alarm 36 is activated.

Such a time integral system has many benefits. For example, consider the case where two valid codes are received from two different users in quick succession. In this case, a different pre-set threshold value may be selected in the time integral thresholding means, the second threshold value corresponding

to the maximum time allowed for two users to transit the barrier. Hence, the two users may transit the barrier together without the need for the barrier to shut, re- lock, and then re-open for the second user. However, if only one code is received then the first lower threshold level is selected corresponding to one transit, and hence two people transiting should be detected. By integrating the signal within the time thresholds selected, then signal flicker caused by, for example, one person leaving the barrier just before the second person enters it can be avoided. The time integral thresholding means can contain a look-up table containing the threshold values required for many users at once. In this way, multiple authorised users can be accommodated at once.

The present invention therefore presents an electromechanical locking system which improves upon all of the prior art. The distributed nature of the system and active signalling provide for robust operation and improved redundancy. For example, with a centrally controlled system then an error in the central control may result in all barriers being inaccessible at once. The distributed nature of the present invention overcomes this problem. Furthermore, the present invention prevents a variety of techniques for overcoming the contention problems met when multiple users attempt to simultaneously access the barrier, and also presents a means of detecting unauthorised access through a barrier. By combining the various described elements of the present invention as described, an adaptable and robust electromechanical lock system suitable for domestic or commercial use can be obtained.

While the above description has been given in relation to the passage of a person through a barrier it will be appreciated that with some modification the above system could be applied to any animate or inanimate object passing through a barrier. The term person and personnel should be interpreted accordingly in the light of this.