FR2768227A1 - Protecting information technology equipment - Google Patents

Abstract

Equipment such as a microcomputer (10) may be protected from misuse or robbery by using an insert (4,40) between the normal plug and the wall socket (p). The supply current and the state of contacts (44,52 ) is sensed (510, 530) and radio signaled (500) to a remote station which detects use at a wrong time or robbery. A keyboard may be used to authorize unusual use of equipment.

Description

DEVICE FOR MONITORING AN ELECTRICAL APPARATUS,
IN PARTICULAR OF A COMPUTER UNIT OF A PARK
OFFICE, AND IMPLEMENTATION SYSTEM
The present invention relates to a device for monitoring an electrical appliance, more particularly an appliance operating on the mains and comprising a power cord intended to be plugged into a wall outlet or the like.

 The invention also relates to a system for implementing this device.

 The preferred field of application of a device according to the invention, although not exhaustive, relates to the monitoring of the computer units of an office park.

 In the context of the invention, the term "unit" must be understood in its most general acceptance: microcomputer, server, display screen, printer, and in general, any peripheral.

 A first application of the device according to the invention is to be able to compensate for the theft of the monitored device, at least to detect attempted thefts and, advantageously, to launch an alarm.

 A second application is to detect fraudulent use of a monitored device, or at the very least non-compliant. It may be, for example the use of an IT resource, by an unauthorized person and / or outside of predetermined time slots.

 A third application concerns the "hacking" of data, in the most general sense that one can give to this term. It consists in monitoring or even preventing the use of protected software and / or access to locked information.

 To fix the ideas, we will first place ourselves in the case of the application which will be called "theft prevention".

These last few years have seen the rise of computer systems, in particular microcomputers and / or local data processing networks which allow a great concentration of the data and information processed, and recorded (in magnetic and optical form), this under a small volume. The portable microcomputers illustrate this last technical characteristic in a remarkable way. On the other hand, equipment prices fell very sharply, which had a cumulative effect, as the rate of equipment in computer equipment, and in particular office automation, of companies increased sharply. The fleets of large and medium-sized enterprises have therefore grown. Likewise, small or very small businesses, shops or liberal professions have, for the most part, at least one microcomputer and one or more peripherals (printer, modem, etc.).
there follows a double risk: the theft of the material and the disappearance of the stored data and information.

Even if the price of equipment has dropped sharply, the fact remains that the theft of a microcomputer remains an appreciable damage, an aggravated damage if we add the theft of associated peripherals. The disappearance of stored data and information can be even more penalizing, or even have irreparable consequences, because it can be essential to the life of the company. Normally, periodic backups of the data should be made. On the one hand, this is not always the case and, on the other hand, the backup unit can also be stolen. This loss of data can be simply due to the theft of the coveted equipment, but also result from a malicious act, the "support", that is to say the material, having been stolen only incidentally, so to be able to appropriate the data (in situ copies proving impossible or very difficult to make).

 To avoid, or at least to delay or make more difficult the theft of the aforementioned devices, various methods and devices have been proposed. Among these, we can cite the following: metal hoops surrounding the device and screwed to the support table, steel cables, provided with a padlock, and which moor to the floppy disk drive of the microcomputer, magnet devices and audible alarms, for example used in supermarkets, and tattoos, produced similarly to the engraving of automobile windows.

 These devices have several drawbacks: the device to be monitored or its support must be adapted (drilling holes), they are not discreet.

For the most part, they make it difficult for devices to be moved by persons authorized to carry out these movements, whether for use in another place or to carry out maintenance in the workshop.

On the other hand, many devices require the use of keys, which can be lost or must be duplicated, if several people are authorized to move the devices, which greatly reduces the efficiency that can be expected from a such system. Finally, we can also note that the effectiveness of tattoos is very limited if the device (even a portable model) has been stolen for later private use.

 Finally, these devices do not make it possible to ensure other functions than the prevention of attempted thefts. In particular, they cannot provide monitoring functions for abnormal use in situ or access to reserved software or data, with the exception of the padlock device locked on the floppy flap door and which only prohibits the use of this integrated device.

 The object of the invention is to propose a device for monitoring electrical devices, in particular computer units of an office park, which does not have the drawbacks of the devices of the known art and which not only makes it possible to prevent the theft or to detect attempted theft, but also to detect and / or prohibit abnormal use of these devices.

 To do this, the device according to the invention is based on monitoring the energy state of the electrical current supply to the devices. More specifically, the device essentially consists of a box comprising electronic circuits detecting the passage or not of the electric current in the power cord of the device to be monitored. This box simply plugs into the electrical power supply socket (for example wall), which will simply be called "mains socket" below. It also advantageously comprises at least one intermittent contact making it possible to detect the disconnection of the power cord. The case can be presented in a very small volume and be provided with appropriate shapes which make it very discreet, in other words which do not attract the attention of an unsuspecting person.

 In addition, it does not require any adaptation of the electrical equipment to be monitored, nor of its support.

 We can therefore detect the passage of the supply current and use this information for various types of applications, whether it is theft prevention or the detection of abnormal uses.

 In the preferred field of application of the invention, which relates to the monitoring of computer units, the power cords usually used are removable and comprise four conductors, two mains supply conductors, one earth conductor and a fourth conductor. not active. The plug on the device side is a specific female plug which, when disconnected from the male plug of the device, establishes temporary contact between the fourth conductor and the earth conductor. The invention takes advantage of this characteristic. In this preferred application, the electronic circuits of the box also monitor the appearance of this galvanic contact between two conductors and can use this information to detect an attempt to remove the device.

 In a first variant embodiment, the device according to the invention is associated with transmission members, unidirectional, or preferably bidirectional, which make it possible to pass on incident detections to a central station, be it a surveillance station, under operator control (light board for example), a central computer system or a telephone exchange. If the transmission device is bidirectional, the device can receive commands and / or instructions from this central station, for example to cut off the electrical energy supply for an application for monitoring the conditions of use of the device (time slot not authorized, etc.).

 The link mode can call on various technologies: radio transmission, carrier currents, telephone links in pairs, serial type computer bus, optical fibers, infrared beam transmission, magnetic loop, etc.

 In a second alternative embodiment of the device according to the invention, it is associated with an alarm, audible or visual.

 In an additional variant embodiment, an electronic unlocking device is provided (for example a keyboard, a card reader, etc.), so that an authorized person can enter an identification code, which will allow him take the aircraft without triggering an alarm or, at the very least, without detecting an attempted theft.

 The invention therefore relates to a device for monitoring an electrical appliance comprising an electrical energy supply cord comprising at least two supply conductors, characterized in that it comprises a box to which said cord is connected. power supply and in that said box comprises electronic circuits comprising at least one current sensor detecting the passage of current in at least one of said conductors so as to generate a signal representative of the energy state of said electrical appliance to be monitored and circuits for operating said signal representative of the energy state and generating an incident signal on detection of a predetermined variation of the signal representative of the energy state.

 The invention also relates to a system implementing this device.

The invention will be better understood and other characteristics and advantages will appear on reading the description which follows, with reference to the appended figures, among which
- Figures 1 and 2 illustrate an example of a device for monitoring electrical devices according to a first embodiment of the invention;
- Figure 3 schematically illustrates the configuration of a removable cable used in office automation
- Figures 4a to 4e illustrate examples of devices for monitoring electrical devices according to four additional embodiments of the invention;
- Figure 5 schematically illustrates an example of system architecture implementing monitoring devices according to the invention;
- Figure 6 schematically illustrates an example of a central monitoring station for a system according to Figure 6
- And Figure 7 illustrates an example of a device for monitoring electrical devices according to an additional embodiment of the invention, for bidirectional transmissions
To fix ideas, we will first place ourselves within the framework of the preferred field of application of the invention, in this case the monitoring of computer units.

 FIG. 1 schematically illustrates a computer station 1, reduced to a microcomputer 10 and to its display screen 11, the whole being placed, in a conventional manner, on an appropriate support 2 (table or other). It is assumed that the microcomputer 10 and its screen 11 are connected to the mains, via their power cord respectively 100 and 110, plugged into a wall outlet of a power panel 3. In the example described, the panel 3 includes three mains sockets, pl to p3, of which only two, P2 and p3, are used.

 More specifically, according to an important characteristic of the invention, the cords 100 and 110 are associated with monitoring devices according to the invention, two of which have been shown 4a and 4b. In the example described, the monitoring devices 4a and 4b are shown separate from the wall sockets pl to p3, but could just as easily be integrated into these sockets. they could, for example be arranged behind the cover of the power supply panel 3, which would make them even more discreet.

 FIG. 2 schematically illustrates the general structure of a monitoring device 4 according to the invention. it comprises a housing 40 enclosing electronic circuits 5 for detection, control and, optionally transmission and / or reception of signals.

 In the alternative embodiment shown in Figure 1, the housing 40 is plugged into a wall outlet, here referenced p. In reality, the box 40 serves as an intermediary between the wall outlet p and the male plug 101 of the power cord 100 of the device to be monitored, here 10. The box 40 therefore has at one end, in the variant shown, two male pins 41 and one female pin 42 (for the earth), arranged in space so as to allow insertion into the wall socket p. It should be understood that, although shown in a plan for the sake of clarity of the drawing, the pins correspond to the geometry of the wall outlet, according to the standards in force in a given country of use. At the other end, the housing 40 has a female type plug, comprising two female pins 44, a male pin (for the ground), as well as an additional contact 46, into which the male plug 101 of the cord is inserted. power supply 100 to the device 10. Pins 41 and 42 are connected by conductors 43. Pins 42 and 45 are advantageously connected to the ground of the housing 40 or connected by an additional conductor (not shown), to ensure continuity earthen.

 According to a first characteristic of the device 4 according to the invention, the electronic circuits 5 measure the intensity of the current i supplying the device to be monitored (for example the microcomputer 10), or at least detect the passage of this current. To do this, a current sensor 51 is used. In the example illustrated in FIG. 2, it has been assumed that the current sensor 51 was based on the magnetic coupling between one of the conductors connected to the mains and a coil threaded on this conductor. . One can also use, on a similar principle, a transformer, the primary of which would be constituted by one or more turns of this conductor. Such an organ has the advantage of offering good decoupling between the high mains voltage and the electronic circuits 5, users of the signal received. However, other types of sensors can be used: optoelectronic coupling device, Hall effect semiconductor or measurement of the current passing through a low series resistance. In the latter case, it will generally be necessary to provide galvanic isolation between the sector conductors and the electronic circuits 5. The sensor 51 is connected to a measuring member 510, included in the electronic circuits 5. Generally, this measuring member 510 also ensures the conversion of the measured signals into digital signals, more easily exploitable by information processing circuits.

 The electronic circuits can be supplied autonomously, using cells or batteries, and / or via the mains. To do this, as shown in Figure 2, there are provided supply conductors 46 connected to pins 41 and an internal power supply 47, providing one or more DC voltages, voltages necessary for the proper functioning of the internal circuits.

 The electronic circuits 5 must reflect the signals measured or detected in one way or another, so that they can be used. To do this, as indicated, various transmission techniques can be used. In the example illustrated, it has been assumed that the transmission to a central station (not shown), the nature of which will be specified below, is carried out by radiofrequency waves. The electronic circuits 5 are therefore provided with a radio-emission member 500 and an antenna 50. It is clear that, if the housing 40 is made of metal, it is necessary that the antenna 50 is external to the housing 40. However, as will be shown below, the frequencies used being very high, the dimensions of the antenna circuit are very small. In a preferred embodiment, the transmission is of the bidirectional type, which also makes it possible to receive control signals and / or instructions that can be used by local data processing circuits, that is to say included in the circuits. 5 (for example a microprocessor, a microcontroller or a similar circuit, associated with memory circuits).

 Depending on the function assigned to the device 4, the signal received by the electronic circuits 5 is used, a priori, specifically. One can, for example, detect attempted thefts, the apparatus 10 being on, if the signal measured by the sensor 51 drops to zero. In fact, when the device 10 is in service, the sensor 51 detects the passage of a current i, which can be of variable amplitude depending on the load of the device, but which is not zero. If one of the following organs the device 10, the plug 101, or even the device 4, is disconnected or disconnected the signal measured by the sensor 51 drops to zero. the same applies if the cord 100 is disconnected from the device to be measured, insofar as the cord 100 is removable. The variation of the signal (fallout) is passed on to a central station, by the aforementioned radio frequency link, for appropriate operation of the alarm, etc., which will also be detailed below.

 In the case of monitoring the abnormal use of the device 10, for example outside of an authorized time slot (outside working hours, at night, etc.), it is on the contrary the rise in the signal that can be significant. Indeed, this rise indicates the start of the device. It is also possible to monitor, centrally, non-compliance with instructions: for example a device shutdown instruction when an employee leaves their work station. If the signal detected and passed on to the central station is still in the "high" state after a given hour, this means that the device has remained on.

 For the application for detecting an "attempted theft", the description which has just been made assumes, for it to have effective detection, a change in state of the signal detected by the sensor 51. If the device does not is not in operation, disconnecting the plug 101 or the cord 100, if it is removable, does not cause any change of state. Also, according to another characteristic of the invention, the device 4 is provided with a second detector, which advantageously comprises a pair of galvanic contacts 52, connected by conductors 53 to a polling member 530 of the state of these contacts 52, included in the electronic circuits 5. This member 52 detects the physical presence of the male plug 101 of the cord 100, for example of at least one of the male pins 44. The electronic circuits 5 scan, conventionally per se, the 'state of the aforementioned pair of contacts, closed or open state. it should also be noted that the pair of contacts can be either in the open or closed state when the plug 101 is inserted in the housing 40, only the change of state is significant.

 This latter arrangement does not, however, detect the disconnection of the cord 100, device side 10, if the latter is removable.

 Also, in a preferred embodiment, a third sensor is provided.

 To do this, the invention takes advantage of a particular feature of the structure of the removable power cords used in office applications. Such a structure is illustrated diagrammatically in FIG. 3. The cord 100, for an appliance to be connected to earth, actually comprises four conductors: two actual supply conductors 102 and 103, an earth conductor 104 and a conductor 105. The conductors 102 to 103 are arranged inside an insulating sheath 106. The conductors 102 and 103 are connected, on the male plug side 101, to male pins 1010 and 1011, respectively, and on the female plug side removable 107, to female pins 1020 and 1030, respectively. The earth conductor 104 is connected, on the male plug side 101, to a female pin 1012 and, on the removable female plug side 107, to a female pin of particular configuration. The additional conductor 105 is connected, on the male plug side 101, to an external metallic contact 1013, on the removable female plug side 107, to the same female pin of particular configuration. The female plug 107 is intended to be plugged into a socket 1000, embedded in the cover of the device 10, comprising three male pins 1001 to 1003.

The ground pin of the plug 107, with a particular configuration, actually comprises a pair of contacts 1050 and 1040, which establishes a galvanic continuity between the conductors 104 and 105, and deletes it when the plug 107 is removed from the socket 1000.

 This pair of contacts 1040 and 1050 therefore plays a role similar to the pair of contacts constituting the sensor 52, internal to the housing 40. The housing 40 is provided with a wiper 46, intended to establish galvanic contact with the pad 1013, and the electronic circuits 5 are connected to the pin 45 and to the wiper 46, by a pair of conductors 54. The electronic circuits 5 comprise a second circuit 540, for scanning the state of the contacts 1040 and 1050. This circuit detects the disconnection of the cord 100, and more particularly of the plug 107, by the appearance of a galvanic discontinuity between the conductors 104 and 105. It can therefore be said that the sensor, or at least the detection or measurement member, is offset , in fact, in file 107, at the end of cord 100.

 If the device 4 is not integral with the wall socket p or integrated in this socket, and if the device 10 is not in operation, the fact of disconnecting the device 4 from the wall socket cannot be detected by any previous sensors. There is no modification of the amplitude of the measured current i, nor modification of the state of the contacts 52 or 1040-1050.

This problem can be solved by the device of the invention in at least two ways
A first solution consists in permanently transmitting a particular signal, for example a signal identifying a given unit among all the others.

The emission of this particular signal must be subject to the presence in the housing of the mains voltage. In other words, the supply of the specific circuits for generating this signal must be provided by a voltage derived therefrom, even if, moreover, the electronic circuits are provided with an autonomous supply. In this case, disconnecting the device 4 stops the transmission of the particular signal. This information can therefore be used again to prevent theft, or at least to detect an attempt to steal or remove the device 10 (or any other device) by unauthorized personnel can be presumed.

 A second solution consists in providing an additional sensor (not shown), similar to the sensor 52, but detecting the physical presence of the device 4 in the wall outlet p. To do this, one can provide a pair of contacts actuated by the male earth pin of the wall outlet. An example of such a sensor will be described below with reference to FIG. 4c. The detection of a change in the state of these contacts signals the withdrawal of the device 4 from its housing. it is then necessary to have an energy flywheel, at least temporary, to emit an alert signal after this detection, even if the device is only powered by the mains. A charged electric capacitor, of sufficient capacity, can provide this temporary energy storage function and allow the emission of an alert message.

 In order for the signals transmitted to be usable, in particular for large installations comprising several tens or even hundreds of devices, distributed in different rooms or even in different buildings, it is essential to identify, without ambiguity, the device that issued an alert or incident signal. it is indeed essential to precisely locate the incident, or even the nature of the incident if the devices 4 include several types of sensors.

 To do this, binary words of sufficient length are used. These binary words include at least one identification code of the device, that is to say its address in computer terminology. As indicated, the identification code can be issued continuously, which also makes it possible to ensure that the device functions correctly, at least as regards its transmission circuits. In another operating mode, the device 4 only transmits if an incident is detected. The identification code can be assigned in situ, but this requires the disassembly of the housing 40, since an unauthorized person should not be able to modify it from the outside. Also, in a preferred embodiment, the identification data of the device 4, that is to say its address, are recorded, at the factory, in a fixed memory, of the "ROM" type for example, or semi fixed, of the "PROM" type, if one wishes to keep the possibility of reconditioning the monitoring devices.

 It may be necessary to complete the identification code with auxiliary information.

By way of example, a first item of information can identify a particular sensor, that is to say its "address", if there are several sensors present in the housing 40. The number of sensors being however limited, some bits are sufficient to perform this function. Most sensors operate in "all or nothing" mode. A single bit is therefore sufficient to completely determine the state of this type of sensor. On the other hand, the current sensor 51 can operate, either in "all or nothing": detection of the passage or not of current, or actually in measurement of the intensity of the current i (ammeter sensor). In the latter case, the circuits 510 must include an analog-digital converter supplying a word of length proportional to the precision of the measurement to be carried out. This last possibility makes it possible to appreciate, in particular, the operating mode of certain devices.

It has no particular utility for the "flight attempt detection" application, unless several devices are plugged into the same outlet, for example via a common device. This is the case for certain screens whose electrical current supply is provided by a connection to the central unit. In the majority of cases, it is not a question of actually making current measurements, but of determining discrete values of intensity, that is to say of absorbed energy levels, in very limited numbers. The number of bits required therefore also remains very limited.

 Finally, as in any transmission, it may be necessary to add to the "useful bits", depending on the protocol used, so-called service bits (header, etc.), parity bits or redundancy bits (code error detection and / or correction), etc.

 By way of nonlimiting example, one can choose a binary word of length 48 bits, which offer 248 distinct binary combinations. On the other hand, such a word length does not present any difficulty as regards the capacity of the memory circuits, even if the dimensions of the case are very small.

 The device according to the invention is susceptible of additional variant embodiments.

 In particular, it is possible to add a local, optical or preferably audible alarm 6, as illustrated diagrammatically in FIG. 4a. This arrangement may prove to be advantageous, in particular for small installations, that is to say installations comprising only a limited number of devices to be monitored, and preferably well located. In this case, it may be possible, for certain applications, not to provide the circuits for transmitting signals to a remote site.

 Another alternative embodiment of the device according to the invention, illustrated diagrammatically in FIG. 4b, consists in providing the device 4 with an electronic unlocking member. This member may consist, as illustrated in FIG. 4b, of a keyboard 7 for entering and entering data. An authorized person may move the device to be monitored or operate it (if access to this device is reserved), without the issue of an incident detection signal or the triggering of a local alarm, for example an audible alarm (if the device is also provided with an alarm 6, in the embodiment of FIG. 4). To do this, it suffices to enter a personal identification code, using the keyboard 7. It is also possible to use an electronic key, for example constituted on the basis of an "electronic chip" comprising a fixed memory, of the "ROM" or reprogrammable type of the "PROM" or "EPROM" type. Such electronic keys are commercially available, under various references. In place of the keyboard or the electronic key 7, a card reader (not shown) can be used, the card being of the magnetic strip type or of the so-called electronic "chip" type. We can also combine the two means. Access authorization codes can be stored locally and authorization given by information processing circuits (included in electronic circuits 5) also local, after verification of the code entered. But to obtain greater operating flexibility, we prefer centralized processing. In this case, the personal identification code or password entered is transmitted to a remote central station, by the transmission circuits 500 of the device 4, in plain text or in encrypted form. This latter arrangement is facilitated if the card is of the electronic "chip" type. One can then use a conventional algorithm, similar to that of bank cards, for example the "RSA" encryption algorithm. It is also necessary to transmit the identification code of the device 4 associated with the device to be monitored. The comparison of the data transmitted with authorization lists (persons) and possible authorization levels (equipment, programs, data stored with reserved access) is then carried out centrally. On the other hand, it is necessary for the transmissions to be able to be carried out bidirectionally, so that in return the monitoring device that issued the request receives command and / or instruction signals authorizing the requested operation.

 FIG. 4c illustrates an additional variant of the device according to the invention, a variant more particularly suitable for monitoring electrical devices provided with a removable power cord. The elements common to the previous figures have the same references and will only be described again as necessary.

 In this case, the device, referenced 4 ′, advantageously comprises an integrated cord 100 ′ which replaces the original cord. It ends as before with a female plug 107 '. In the example described, it is assumed that the device to be monitored (not shown) does not need to be earthed. The cord 100 ′ is therefore two-wire. The p 'wall outlet does not have a grounding prong. it should however be understood that the configuration described allows earthing. it suffices to provide appropriate sockets and plugs and an additional earth conductor, as in the case of device 4 in FIG. 2.

 In the example described in FIG. 4c, the electronic circuits 5 measure the supply current using a sensor comprising a current transformer 51 ′, the function of which is quite similar to that, 51, represented in FIG. 2 The disconnection of the device 4 'from the wall outlet p' can be detected, either by the presence of the mains voltage supplying the circuits 5 (conductor 46), as before, or by an additional sensor 55, for example a pair of contacts 550, actuated by a plunger core 551 with spring, pressed in and closing the contacts 550, when the device 4 'is plugged into the wall outlet p'. A circuit 552 continuously scans the state of the contacts 550.

 In the case of a two-wire supply, the disconnection of the socket 107 ′ cannot be detected if the device to be monitored is not in operation.

The "theft prevention" application can however be completely filled if a grounded cable of the type described in FIG. 3 is used, because one can integrate into the electronic circuits 5, a scrutinizing circuit identical to the scrutinizing circuit 540 of FIG. 2 .

 Figures 4d and 4e illustrate an additional variant of a device according to the invention 4 "for monitoring the use of certain computer peripherals, such as a keyboard 12, a mouse 13, a digitizing tablet (not shown ) or any similar device connected to the central unit 10 of a microcomputer 1.

 In FIG. 4d, it has been assumed that the central unit 10 of the microcomputer 1 and its screen 11 were supplied by a single cable 100 '(the screen 11 being connected to the central unit 10). It has also been assumed that the device 4 "is similar to the device 4 'in FIG. 4c, in that the cord 100' replaces the original power cord of the central unit 10. The device 4" is therefore attached to the end of the power cord 100 '. The detection of the disconnection of the cord 100 'is carried out in accordance with what has been described with reference to FIG. 4c, and there is no need to rewrite the process.

 On the other hand, according to the main characteristic of this variant embodiment, one or more peripherals, such as the aforementioned keyboard 12 or mouse 13, are connected to the central unit 10 by means of the device 4 ". Provision is made, for to do this, appropriate sockets on the housing 40 "of the device 4", for example a female socket 128, of the "DIN" type, for connecting the male socket 121, termination of the connection cord 120 of the keyboard 12. Similarly, in the example described in FIG. 4d, a female socket 132, of the "DB9" type has been provided for connecting a second connector 131, termination of the cord 130 of a mouse 13.

 In FIG. 4e, the interior of the device 4 "has been shown. For reasons of simplification, it has been assumed that a single device, the mouse 13, is controlled by the device 4", it being understood that several devices can be controlled as shown in Figure 4d. Similarly, the circuits for detecting the energy state of the electrical current supply to the microcomputer 1 have not been shown. These circuits are produced according to any of the variants described above, and there is no need to call them back.

 A bundle of internal connections 133-134 establishes a wire-to-wire connection between the input connector 132 and an output cable 135. The latter comprises a conventional male end connector 136 which plugs in place of the connector 131 , on the mouse input connector 137 of the central processing unit 10 of the microcomputer 1. More precisely, the beam 133, at the output of connector 132, is connected to the beam 134, and therefore to the cable 135, via a bank of switches K, advantageously produced on the basis of semiconductor electronic switches.

 According to another characteristic of the invention, the state of the active links of the beam 133 is scanned by appropriate electronic circuits, for example under the control of the microprocessor CPU integrated in the electronic circuits 5. The term "active link" means any link which carries signals transmitted from the peripheral, for example the mouse 13 in the example described, to the central unit 10. If it is a serial link, it is sufficient to monitor a single wire of the bundle 133. The microprocessor CPU also receives time base signals generated by specific circuits H (FIG. 4e) or generated from its own clock circuits (not shown).

 If the microprocessor CPU does not detect any activity on the monitored device for a predetermined period of time, it generates a signal Sk controlling the switching of the switches K, which has the effect of cutting the connection between the input beam 133 and the beam of output 134. it also follows that the monitored device, in this case the mouse 13, no longer has any action on the central unit 10. In the case of a serial type link, a single switch K is necessary. Advantageously, the signal Sk is a binary signal with two states, a first state causing the opening of the switches K, a second state closing these switches K.

 In this way, it is possible to automatically prevent the use of the input peripherals of a microcomputer 1, by persons or under unauthorized conditions. For example, if an authorized operator leaves his workstation, the microprocessor CPU detects an inactivity of the monitored device (s). When the predetermined time interval has elapsed, it generates the control signal Sk and thereby deactivates these peripherals.

 Unlocking the previously locked peripherals can be obtained by again using a keyboard 7, an electronic key, a chip card reader or any similar device, as described in relation to FIG. 4b. Still by way of example, the authorized operator who has left his post, for a period of time greater than the predetermined time interval, re-enters his personal identification code or his password. After verification of these data, the signal Sk returns to the second state and the connection between the beams 133 and 134 is re-established. The mouse 13, and more generally the peripherals monitored, are unlocked.

 In an additional variant (not shown), the signal Sk cuts the current supply to the microcomputer 1, in a similar manner to that which will be described below in relation to FIG. 7, by using an electromagnetic relay whose contacts are placed in series with electrical power supply wires.

 We will now describe an example of a system using one or more devices according to the invention.

 It is assumed as above that the links are made by radiofrequency waves. To simplify the drawing, it was also assumed that the fleet to be monitored included two devices Apa and Apb, located in a first room S1 of a building, and two other devices, APC and Apd, located in a second room S2. Finally, it is assumed that the central monitoring station 9 is located in a third room S3.

 In a preferred embodiment, the links are of the bidirectional type. The monitoring devices 4a to 4d, associated with the Apa and Apd devices, comprise transmitting circuits as indicated with reference to FIG. 2. To avoid, or at least minimize, any risk of interference with neighboring systems ( other buildings, other companies), the range of transmitters is advantageously limited to a few tens of meters, typically 30 m. In the case where the range is insufficient to reach the central monitoring station 9, it is possible to use intermediate relays 8, consisting of transceivers, possibly with very directive radiation patterns. In FIG. 5, the devices 4c and 4d are in direct communication with the central monitoring station 9, while the devices 4a and 4d are relayed by the transceiver 8. The reverse links, in the case of bidirectional transmissions, a priori take the same paths.

 The central monitoring station 9 can be of different types.

 According to a first alternative embodiment, it can essentially comprise a light table under the control of an operator, possibly associated with an audible alarm drawing his attention when an incident is detected by at least one of the monitoring devices.

The lighting of an indicator light then indicates to the operator the location of the incident detection so that he can intervene and / or trigger an alarm, according to pre-established instructions. It is naturally necessary that the central station is equipped with transmission and / or reception circuits, and with decoding circuits for messages received from the monitoring devices, to locate the call (address) and, possibly, the nature of the incident. (case of multi-sensor devices). These circuits are known per se to those skilled in the art and there is no need to detail them further.

 According to a second alternative embodiment, the central monitoring station can be constituted by a computer system, for example a microcomputer or a local network, coupled to circuits for transmitting and / or receiving radiofrequency waves by a specialized port. .

In the latter case, one can have recourse to the standard "IEEE 802.11" (in the course of standardization) which defines a communication protocol and a range of authorized frequencies: ranges 2446.5 MHz to 2483.5 MHz; according to two main modulation algorithms: frequency hopping ("FHSS" for "Frequency Hopping Spread Spectrum") or fixed frequency ("DSSS" for "Direct Sequence Spread
Spectrum "). Specialized cards exist in the trade and can constitute an entry point on the aforementioned local network.

The processing of the received signals can be carried out fully automatically, under the guidance of a recorded program, or the processing can be, as before, under the control of an operator. In this case, at least one display screen is provided.
it is also advantageous that the installation and operation of the system can be carried out by non-specialized personnel. We will therefore advantageously use pictogram-type displays as illustrated diagrammatically in FIG. 6. In this example, the operator has a computer screen 90, on which the plan of the building is displayed and, under form of pictograms (the appearance of which may change following the detection of an incident by one of the devices), the location of the devices to be monitored PC1 to PC4, distributed in the rooms here called "Room 1" and "Room 2" . Zt text zones can be provided displaying various messages depending on the application considered: for example instructions intended for the operator according to the incidents detected, their types, etc. One can also provide a voice synthesizer guiding the operator.

 In theft detection or prevention applications, most often the operator will have to intervene personally, warn other people (guard station, etc.) or trigger an alarm. This can also be the case for other types of application monitoring the legal or illegal use of a device, recorded software or reserved data.

 On the other hand, for applications of the latter type, if the links allow bidirectional data transmissions, the operator can intervene for the device to be monitored, via the associated monitoring device. it suffices to send an order to this device, for example an order causing the mains supply to be cut off.

 To do this, it is naturally necessary that the message sent by the central station 9 includes address information identifying one or more particular monitoring devices, a priori at least the monitoring device that has detected an incident. It is also necessary that the transmission circuits 500 of the electronic circuits 5 are supplemented by reception circuits, the antenna 50 being able to be used for these two functions. The electronic circuits 5 must also include a decoder circuit (not shown) making it possible to recognize among all the messages sent by the central station its own address and, following this recognition, allow it to accept the only messages which are intended for it.

 For the command issued to be effective, it is necessary to provide switching circuits inside the housing of the monitoring device. FIG. 7 is a partial view of a monitoring device 4 ′ comprising such a switching circuit 56, constituted for example by an electromagnetic relay 561 controlling a contactor 560 in series with one of the supply conductors, this relay being actuated by control circuits 562 receiving the instructions decoded by the electronic circuits 5. It is also possible to use semiconductor switches such as power transistors, operating on or off, thyristors or triacs, which makes it possible to obtain a reduced volume for the device housing.

 Command messages can be sent automatically, under the command of a recorded program, for example, or by human intervention, possibly program-assisted. To do this, the operator can have a conventional computer keyboard 91 (FIG. 6) or a set of preprogrammed keys. he can also have a mouse 92 and click on one of the pictograms displayed (for example the one corresponding to the monitoring device that triggered the alarm), so as to initiate a pre-programmed action display of a list of instructions intended to the operator, automatic sending of a command to the aforementioned device, etc.

 According to a third alternative embodiment, the central monitoring station can be constituted by a telephone exchange, or more precisely comprise computer means integrated in this telephone exchange.

In this case, the call generated by monitoring devices can either be processed in situ by the operator (after display on a light panel or on a screen, for example), or automatically retransmitted to one or more remote telephone sets, or more generally at a remote monitoring station (security company, etc.). The retransmission can also be carried out according to the usual remote monitoring techniques, for example by successive calls to telephone numbers from a pre-established list, according to a predetermined order of priority.

 On reading the above, it is easy to see that the invention achieves the goals it has set for itself.

 The monitoring device according to the invention is very simple to use and install, and does not require the intervention of specialized personnel. just plug it into a regular wall outlet or equivalent. it does not require any adaptation of the equipment to be monitored, nor of their supports (table, desk, etc.).

In the case of office equipment, in one of the variant embodiments for which the device incorporates the power cord, it suffices to replace the original cord with that of the device.

Similarly, for the implementation system, with the exception of the initial installation, no specialized personnel is required. It should also be noted that most of the operations carried out during the initial installation are limited to routine operations. Finally, with regard to the programs, these can be preloaded in the IT devices delivered. The same applies to the frequencies used and the addresses of the monitoring devices, these parameters being able to be determined at the factory.
it should be clear, however, that the invention is not limited to only the examples of embodiments explicitly described, in particular in relation to FIGS.
it should also be clear that, although particularly suitable for applications in the office automation field, the invention cannot be confined to this single type of application. It generally applies to the monitoring of any electrical device comprising an electrical power supply cord, either to prevent or detect attempted theft, or to monitor the use of these devices under predefined conditions. By way of nonlimiting example, we can cite the surveillance of televisions made available in hotel rooms, whether to avoid attempted theft or counting time of use, the surveillance of photocopiers in a company , to avoid their use outside predefined time slots, monitoring the proper functioning of various electrical devices by means of information indicating that they consume electrical energy, etc.

Claims (15)

 1. Device for monitoring an electrical appliance (10) comprising an electrical energy supply cord (100) comprising at least two supply conductors (102-105), characterized in that it comprises a housing (40 ) to which said power cord (100) is connected and in that said housing (40) comprises electronic circuits (5) comprising at least one current sensor (51, 510) detecting the passage of current (i) in at least one of said conductors so as to generate a signal representative of the energy state of said electrical appliance to be monitored (10) and operating circuits of said signal representative of the energy state and generating an incident signal on detection a predetermined variation of the signal representative of the energy state.  2. Device according to claim 1, characterized in that said current sensor comprises a magnetic coupling member (51) generating at output a signal proportional to the electric current (i) passing through said supply conductors and a circuit (510) transforming said output signal into a signal of a first level when said device to be monitored (10) is supplied and the passage of a current (i) is detected, and of a second level, when the device to be monitored (10) is no longer supplied, said incident signal being generated when said electronic circuits (5) detect the predetermined passage from one of said levels to the other.  3. Device according to one of claims 1 or 2, characterized in that it comprises a member (6) for generating a local alarm signal, visual or audible, actuated by the appearance of said incident signal .  4. Device according to one of claims 1 or 3, characterized in that it comprises an electronic unlocking member comprising a keyboard (7) and / or a card reader for entering a personal identification code in said electronic circuits (5) so as to inhibit the action of said incident detection signal.  5. Device according to claim 4, characterized in that said apparatus to be monitored being a computer unit (1-10) provided with at least one data input device (12, 13), said housing (40 ") of the device (4 ") comprises a connection member (128, 132) for said peripheral (12, 13), in that it comprises a bundle (133-134) of conductors, internal to the housing (40"), performing a wire-to-wire connection between said connection member (128, 132) and an external connection cable (126, 136), in that said external connection cable (126, 136) is connected to an entry (137) for connection of the peripheral (12, 13) on said computer unit (1-10), and in that said electronic circuits (5) comprise switches (K) placed in series on at least part of said internal conductors (133-134) carrying data signals, called active, and a polling unit (CPU) of said data signals conveyed by said ac conductors tifs, so as to determine the inactivity of the device (12, 13) for a predetermined period of time, to generate a control signal (Sk) of said switches (K), to cut said wire-to-wire connection when said time period is exceeded and to lock the device (12, 13) by making it inactive.  6. Device according to claim 5, characterized in that said peripherals consist of a data entry keyboard (12), a mouse (13) and / or a digitizing tablet, and in that it comprises a member for unlocking (CPU) a peripheral, locked after exceeding said predetermined period of time, controlled by the input of said personal identification code via said electronic unlocking member (7)  7. Device according to any one of claims 1 to 6, characterized in that being connected to an electrical outlet (p), it comprises at least one additional sensor (55) detecting this connection, in that this sensor comprises a pair of electrical contacts (550) and a movable element (551) acting on said contacts (550) so as to establish galvanic continuity when the monitoring device (4) is connected to said socket (p), and in that said electronic circuits (5) comprise a circuit (552) detecting this continuity and generating an incident signal when said continuity is broken.  8. Device according to any one of claims 1 to 7, characterized in that said device to be monitored being a computer unit (10) provided with a removable electrical supply cord (100), said cord comprising two distribution conductors energy (102, 103), a conductor (105) called earth and an additional conductor (105) establishing galvanic continuity with said earth conductor (104) when the cord (100) is connected to said computer unit (10 ) and breaks it when it is disconnected, it includes an additional sensor fitted with circuits (540) detecting the disappearance of said galvanic continuity and generating an incident signal.  9. System for implementing at least one monitoring device (4a-4d) of an electrical appliance (Apa-Apd) according to any one of the preceding claims, characterized in that it comprises a central station monitoring (9) connected to said monitoring devices (4a-4d) by a communication link, in that said electronic circuits (5) of each of said monitoring devices (4a-4d) comprises at least one circuit (500, 50 ) transmitting a message upon detection of an incident and in that said message comprises at least one piece of information identifying the monitoring device (4) having detected said incident.  10. System according to claim 9, characterized in that said communication link is a radiofrequency link of determined carrier, in that said central monitoring station (9) comprises at least one receiver wedged on said determined carrier, in that said electronic circuits (5) of each of the monitoring devices (4a-4d) comprise at least one radiofrequency transmitter (500) transmitting said message on the determined carrier.  11. System according to claim 10, characterized in that said radiofrequency transmitters (500) have a range limited to a predetermined distance and in that it comprises relay devices (8), constituted  of a transceiver fixed on said carrier of  determined frequency, so as to establish a connection  between monitoring devices (4a, 4b) located at  a distance from said central monitoring station (9) more  great that said reach and central station of  surveillance (9).  12. System according to claims 10 or 11,  characterized in that said central monitoring station  (9) includes a computer system for processing  recorded program data, in that this system  IT includes at least one display screen  (90) graphically displaying said devices to  monitor (10) and their location, and that when  said computer system receives one of said messages,  alphanumeric information identifying the device  (4a-4d) having issued an incident signal  are displayed on said display screen (90).  13. System according to claim 12, characterized  in that said communication link is of the type  bidirectional, in that said electronic circuits  ques (5) of each of the monitoring devices (4a  4d) and said central monitoring station (9)  include a transceiver wedged on said  carrier frequency determined, in that said station  central monitoring station (9) further comprises organs  of command issues intended to initiate  operations executable by said electronic circuits  (5) of at least one of said monitoring devices  (4a-4d).  14. The system as claimed in claim 13, characterized in that said command transmission members comprise a data entry keyboard (91) coupled to said computer system and actuable by an operator, in that said electronic circuits (5) of each of the monitoring devices (4a-4d) comprises a member (56) for cutting off the current supply (i) of said apparatus to be monitored (10) and in that said executable operation consists in cutting off said current supply on reception of said order.  15. System according to claims 10 or 11,  characterized in that said central monitoring station  (9) includes a telephone exchange and in that said  messages are retransmitted on a place far from  monitoring by this central, so as to ensure  remote monitoring.