Device for controlling a computer system

PATENT

DEVICE FOR CONTROLLING A COMPUTER SYSTEM

Gérard POPINEAU

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a device for controlling a computer system, preferably of the personal microcomputer type, by means of pointing devices, in particular of the wireless mouse type.

TECHNOLOGICAL BACKGROUND OF THE INVENTION

The control devices of a computer system consisting in moving by means of a mouse, ball or other pointing device, a cursor in order to designate on the system screen an object, icon or item of a menu, representative of 'a function to perform, are well known. If they were originally reserved for professionals working on high-end graphic consoles, they are today the symbol of the democratization of the use of the computer by removing the obligation to have to learn esoteric command languages. Even a child who cannot read yet can play with a computer with a graphical interface.

The manufacturers of pointing devices have therefore sought to make them as pleasant as possible. A constraint, generally annoying, is the presence of the wire connecting the mouse to the central unit, and serving both for data transmission in serial mode and for power supply.

This thread is always too short or clings to the most diverse objects. A wireless mouse is therefore considered an improvement.

<img file="MC200048A1_D0001.tif" />

Such a pointing device is described in European patent application EP0171747, in the name of the company METAPHOR COMPUTER SYSTEMS, published on February 19, 1986. The device transmits its movements and the states of its control buttons to the central unit by means of an infrared light beam amplitude modulated by the sequences of representative binary signals.

The implementation of an infra-red transmission in baseband is extremely simple, but it can appear problems of reception related to the ambient light, which can present spectral components in the near infrared (Sun, incandescent lamps).

An improvement in reception has therefore been sought by using means for concentrating and guiding the light received.

Japanese patent application JP4205129, not HITACHI LTD, published on July 27, 1992, mentions such a system.

Another technical problem is posed by the power supply of the wireless mouse. The removal of the wire constraint leads to another easement; the obligation to periodically recharge the battery before the device stops working. The EPO17747 request provided a partial answer to this problem by transmitting to the central unit an alert message intended for the user.

European patent application EP0849700, by the PHILIPS companies

PATENTVERWALTUNG and PHILIPS ELECTRONICS, published on June 24, 1998, provides wireless power for the mouse via an inductive loop placed in the mouse pad. The mouse wire is removed, but the problem is moved to the supply of electrical energy in the form suitable for the carpet. A new wire is therefore necessary; more the user is limited in his aesthetic choices of this accessory, since the carpet is necessarily of a model specially adapted to the system.

Power supply is not just an issue for computer pointing devices. It arises for all small electronic devices. Generally, batteries are used. Periodic replacement of these can become expensive for the user, and batteries are used more and more commonly, at the cost of a larger initial investment, in particular in a charger.

For low powers, a mixed supply by battery and by solar cell, the battery playing a buffer role, has been known since the appearance on the market of inexpensive amorphous silicon cells. This is the case with calculators or desktop calculators. The devices described in ifi the Japanese patent applications JP56132653 and JP61210828, respectively in the name of the company SEIKO EPSON CORP and of the company CASIO COMPUTER CO LTD, constitute examples among others.

The application of a solar cell power supply to a wireless mouse implementing an infrared connection is described in British patent application GB2292995, in the name of the company PRIMAX ELECTRONICS LTD, published on March 13, 1996.

The improvements in the basic pointing device widely known in the field of microcomputing only concern the individual use of a computer system. There are known possibilities of working in cooperation of several people by the implementation of several central units connected in a network. But even if the work is collective, each person personally controls each central unit by means of their own pointing device.

A system allowing several people to use the same central unit is described in the Japanese patent applications JP8221194 and JP9146703, in the name of the company NTT, published respectively on August 30, 1996 and June 6, 1997. Orders from several mice wireless can be received by a conventional personal computer. For this purpose, a radio transmission technique by time sharing is implemented. The different mice successively transmit their data when they receive an identification code sent by the base station connected to the central unit corresponding to their own codes. The intended use is for education and play.

Japanese patent application JP10040002, in the name of the company NEC, published on February 13, 1998, describes the simultaneous operation of several mice in the same window.

The concept of a set of pointing devices controlling a single computer system presents interesting perspectives, particularly in education.

Unlike the teaching of other disciplines, practical computer science is currently not very suitable for group lessons. The training is rather based on the implementation of practical work sessions, during which the students, in small groups of two or three, practice on a complete microcomputer. To allow a large number of students to benefit from an initiation, considerable material resources are therefore required permanently installed in specialized classrooms, with numerous electrical power outlets.

The wireless mouse systems described above in patent documents JP9146703, JPS221194 and JP10040002, would on the contrary allow a more traditional approach to initiation into

<img file="MC200048A1_D0002.tif" />

handling a computer. Each pupil having a mouse, could, under the guidance of a trainer, learn to use a graphical interface, the image of which could be projected on a large screen by means of an appropriate computer peripheral, such as a video projector, or an LCD tablet suitable for an overhead projector.

The economic advantage is obvious: a single computer system is sufficient, which could be constituted by a portable microcomputer. Specialized rooms are no longer necessary, and equipment can be installed quickly in any room.

However, this economic advantage is somewhat limited by the complexity of the known systems. The data transmission protocols between the mice and the central unit use radio links which force the pointing devices to each include a receiver for receiving synchronization signals. Radio wave links also present many disadvantages in countries where there are binding regulations in terms of frequency bands usable for data transmission. The number of these bands is limited and the remaining bands are extremely congested, requiring the use of very complex data coding methods, to avoid disturbance by a similar system operating nearby.

The use of an infrared link would therefore seem more appropriate, the communication channels by this means inside a room being protected from external disturbances.

In addition, the system could use electronic components having a very wide distribution, since infrared remote controls are of universal use.

The system requires a number of communication channels at least equal to the number of pointing devices, and must be insensitive to ambient light, but modulation techniques having the desired characteristics exist.

We can cite the frequency hopping modulation techniques of a subcarrier, an example of which is given in European patent application EP0342146, in the name of the company TRANSDATA, published on May 11, 1989. The device described relates to only one bidirectional link between an electric meter and a device intended to record the consumption of electricity, and the implemented method could not therefore be directly applied. However, the demodulation method described in this document, using wired electronics, can easily be replaced by processing by equivalent software.

European application EP0924873, on behalf of the company ALCATEL, published on June 23, 1999, describes an algorithm making it possible to detect the response tone for modems and fax machines.

<img file="MC200048A1_D0003.tif" />

This type of algorithm, of the Goertzel type, is well known, and can be applied to the detection of voice frequencies. The significant computing power required involves the use of specialized digital signal processing circuits, such as those manufactured by the company ADVANCED MICRO DEVICES. This company also discloses an improvement of the Goertzel algorithm in the international patent application WO97 / 20438, published on June 5, 1997.

In the technical note DTMF Tone Generation and Detection: An implementation Using the TMS302C54x (Application Report; SPRA096A- May 2000), the company TEXAS INSTRUMENTS, describes the algorithms for synthesizing and detecting signals from a multifrequency system.

It appears from the state of the art as described in the documents cited above, that systems of pointing devices intended for a group of users to control a common computer system are known, but that there exists to date no simple, robust, inexpensive system, using proven and modern techniques, which can really be implemented for teaching purposes, by carrying out an inventive synthesis of the state of the art with a view to obtaining optimal characteristics.

GENERAL DESCRIPTION OF THE INVENTION

The present invention therefore aims to optimize the design of a control device for a computer system.

It specifically relates to a control system of a computer system, i

preferably of the personal microcomputer type, provided, in a known manner, with a graphical interface, and at least one communication port, by a group of users by means of several pointing devices without wire connection with the system, preferably of the wireless mouse type.

Each of the pointing devices is manipulated by each of the users and transmits, by means of a communication channel, sequences of binary data representative of the movements and the states of these pointing devices to an electronic interface unit connected to the communication port.

The control device of a computer system which is the subject of the present invention is remarkable in that the communication channel comprises a plurality of communication subchannels, transmitting with standard modulation speed the sequences of binary data, constituted by a carrier common infrared and a set of subcarriers modulated in

C / amplitude by the binary signals of these sequences. The frequencies of the subcarriers are different for each of the pointing devices, without a common harmonic, and are distributed between a lower frequency and a higher frequency, with intervals at least equal to twice the value of the modulation speed increased by a guard band.

Advantageously, the frequencies of the subcarriers are equal to prime numbers multiplied by a constant coefficient.

In a first embodiment of the invention, a single subcarrier is assigned to each of the pointing devices.

In a second embodiment, each of the pointing devices is assigned two subcarriers modulated in phase opposition by the binary signals of the sequences.

In the first embodiment of the invention, the control system implements pointing devices which each include:

a) a digital signal processing block comprising a microcontroller processing the binary signals

b) an emission block comprising:

- an interchangeable ceramic resonator oscillator tuned to the harmonic N of the frequency of the subcarrier assigned to the pointing device

- a frequency divider by N producing the subcarrier from its harmonic

- a modulator of the subcarrier by the binary signals producing modulated signals

a bandpass filter with a central frequency equal to that of the subcarrier and a bandwidth equal to the decreased frequency interval of the guard band, generating filtered signals from the modulated signals.

- an amplifier supplying one or more diodes emitting an infrared light beam from the filtered signals.

c) a power supply unit comprising:

- a solar cell

- a battery

- a battery charge regulator by the solar cell

- a DC / DC converter

In the second embodiment of the invention, the control system implements pointing devices which each include:

<img file="MC200048A1_D0004.tif" />

a) a digital signal processing block comprising a microcontroller provided with:

- a first program developing the binary signals

- a second program constituting a digital oscillator developing the samples of the modulated subcarriers.

b) an emission block comprising:

- a digital / analog converter for converting the sampled subcarriers

a bandpass filter with a central frequency equal to that of the subcarrier and a bandwidth equal to the decreased frequency interval of the guard band, generating filtered signals from the modulated signals.

- an amplifier supplying one or more diodes emitting an infrared light beam from the filtered signals.

c) a power supply unit comprising:

- a solar cell

- a battery

- a battery charge regulator by the solar cell

- a DC / DC converter.

An additional characteristic of the first embodiment is that the electronic unit comprises:

a) a block for receiving infrared light signals and detecting subcarriers.

b) a frequency demultiplexing block of the detected signals comprising a number of analog bandpass filters in number equal to the pointing devices.

c) a digital signal processing block comprising a microprocessor provided with a communication program generating the binary signals from the demultiplexed signals and transmitting them to the communication port by means of a line amplifier.

An additional characteristic of the second embodiment, which also constitutes a variant of the first embodiment, is that the electronic unit comprises:

a) a block for receiving infrared light signals and detecting subcarriers.

b) a digital signal processing block comprising:

- an analog / digital converter of detected signals

- a microprocessor with an algorithm for extracting spectral information from signals detected by Discrete Fourier Transformation, preferably a two-pole digital response filter

Infinite impulse Q of Goertzel type, and of a communication program elaborating the binary signals from this information and transmitting them to the communication port by means of a line amplifier.

In one or other of the embodiments described above, the line amplifier is bidirectional and transmits to the microprocessor sequences of binary data representative of the movements of an additional pointing device.

Very advantageously, the electronic unit of the control device of a computer system according to the invention comprises a separate part comprising the reception unit, provided with a horn for collecting infrared light beams, and connected by a shielded cable to the part main connected to the communication port.

Contributing to the aims of the invention, the electronic unit comprises a main part in the form of a console with switches allowing the selection of one or more pointing devices and rendering the others inoperative.

A great benefit will be derived from the use of the control device according to the invention, in particular for a computer system comprising:

- a laptop-type central unit

- an LCD tablet type device adaptable to an overhead projector, or a portable video projector

- a set of application software such as office automation, communication, or specific to a function or a trade and when this use is the collective initiation to microcomputing and to collective training for the use of these software.

The advantages of this use are further increased when the computer system furthermore comprises software for simulating a keyboard making it possible to simulate the striking of a key by designating the simulated image of this ladle by means of one of the devices. score.

The users appreciate the use of the device according to the invention when the communication program includes in the binary signals sequences of binary data identifying the sending pointing devices, and when the computer system also includes software assigning a cursor. different shape or color to each of these pointing devices.

These few essential specifications, resulting from the optimal design of the control system of a computer system, make obvious to the skilled person the advantages brought by the invention compared to the state of the prior art.

<img file="MC200048A1_D0005.tif" />

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a diagram of the control system of a computer system by a group of users according to the general concept known from the prior art.

Figure 2 is an explanatory diagram of the frequency multiplexing method implemented in the control device of a computer system according to the invention.

Figure 3 is a simplified electronic diagram of each of the pointing devices of the control device according to a first embodiment of the invention.

Figure 4 is a simplified electronic diagram of the electronic unit of the control device according to a first embodiment of the invention.

Figure 5 is a simplified electronic diagram of each of the pointing devices of the control device according to a second embodiment of the invention.

Figure 6 is a simplified electronic diagram of the electronic unit of the control device according to a second embodiment of the invention.

Figure 7 is a general schematic view of the electronic unit of the control device of a computer system according to the invention.

Figure 8 is a schematic view of the collecting horn that comprises the electronic unit.

Figure 9 is a general view of a computer system using the control device according to the invention.

Figure 10 is a general view showing a preferred use of the computer system of Figure 9.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

The references to Figures 1 to 10 will serve to explain in detail the various features of the invention.

The general concept of the device is illustrated in Figure 1. A microcomputer 1 includes an operating system having a graphical interface which allows users to interact with the system by means of a display screen 2 and devices pointing device 3. The signals emitted by the pointing devices 3 are received by an electronic unit 4 connected to a communication port 5, generally serial, of the central unit 1.

In a common microcomputer system under WINDOWS ®, the pointing devices are mice, or balls which communicate their movements and the actions of the user on i

z

M their control buttons (clicks) to the operating system via an RS232 link. For MICROSOFT ® compatible mice, the X and Y displacements, and the state of the right R and left L button are coded in three words comprising 1 START bit, 7 data bits, and 2 STOP bits, transmitted at 1200 baud . To be compatible with any system under WINDOWS ® by emulating a compatible mouse, the electronic unit 4 therefore has an operating mode in which the binary data sequences emanating from all the mice are transmitted with this format and at this speed to the communication port. series 5.

In a first embodiment of the device according to the invention, all the elements of a standard mouse are used in order to achieve economies of scale. For each of these mice, it is therefore a question of transmitting by infrared a set of binary data sequences having a modulation speed of 1200 bauds. The total number of mice was chosen equal to 32, both for practical reasons (this is the size of a class) and technical reasons (Number of bits of the ports and buses of the microprocessors used).

In a second embodiment, no longer using standard elements, where most of the electronic functions are performed by digital signal processing, a modulation speed of 1200 baud will however be kept for compatibility reasons.

The infrared data transmission technique chosen is a frequency multiplexing technique, in a frequency band limited lower and higher, either by the characteristics of the bandpass filters used in the first embodiment, or by the number of nominal MIPS microprocessors implemented in the second embodiment.

In the embodiment in analog electronics, a single amplitude modulated subcarrier is assigned to each mouse in order to limit the complexity of the electronics unit 4.

The fully digital implementation allows the use of a larger number of filters for demultiplexing without increasing the complexity. Two subcarriers are assigned to each mouse. The two subcarriers are modulated in phase opposition by the binary signals of the bit frames emanating from the sensors of the mouse, that is to say that it is in fact a modulation by frequency hopping ( FSK) greatly increasing the S / N ratio of the transmission.

FIG. 2 shows the distribution of the frequencies of the subcarriers PI, P2 between a lower frequency F1 and an upper frequency F2. To satisfy the Nyquist criterion, the frequency band allocated to each pointing device is at least 2400 Hz .; the interval C1, C2 between each subcarrier PI, P2 is therefore at least 2400 Hz.

us'

The bandpass filters used in the first embodiment are tone decoders, for example of the LM567 type from the company NATIONAL SEMICONDUCTOR. For this circuit, the maximum AF bandwidth is linked to the central frequency FO by the relation: AF = FO / 0.14.

The lower frequency F1 must therefore be greater than 17 KHz.

To avoid that the subcarriers have common harmonics, their frequencies are equal to prime numbers multiplied by a constant coefficient. The following table gives examples of frequencies used for the 32 transmission subchannels in this embodiment.

<td>Channel</td><td>Prime number</td><td>Subcarrier frequency (Hz)</td><td>Clock frequency (Hz)</td>

<td> 1</td><td> 113</td><td> 22600</td><td> 180800</td>

<td> 2</td><td> 139</td><td> 27800</td><td> 222400</td>

<td> 3</td><td> 157</td><td> 31400</td><td> 251200</td>

<td> 4</td><td> 173</td><td> 34600</td><td> 276800</td>

<td> 30</td><td> 617</td><td> 123400</td><td> 987200</td>

<td> 31</td><td> 631</td><td> 126200</td><td> 1009600</td>

<td> 32</td><td> 647</td><td> 129400</td><td> 1035200</td>

The constant coefficient is equal to 200.

The interval C1, C2 between the frequencies of the subcarriers Pl, P2 is approximately 3 kHz, which provides an acceptable guard band B. . The lower limit Fl of the communication channel is Fl = 19600 Hz, the upper limit is F2 = 130900 Hz.

In the second embodiment, using digital oscillators, there are no more constraints on F1 and F2, and the guard band could be smaller. For compatibility reasons, the same frequency distribution has been kept. There are therefore 64 frequencies at an interval of 3KHz from 22600 Hz.

The table above shows a clock frequency.

As shown in Figure 3, each subcarrier Pl, P2 is in fact produced by analog means from its eighth harmonic.

An oscillator 6 stabilized by a ceramic resonator 7 generates a square signal whose frequency is divided by eight by a binary counter 8. The ceramic resonators used are CERALOCK © brand resonators having an appropriate frequency range and precision.

<img file="MC200048A1_D0006.tif" />

The square signal at the frequency of the subcarrier P1, P2 is switched 9 by the binary signals coming from a microcontroller 10 processing the signals coming from the displacement sensor 11 of the pointing device 3, and the buttons 12.

The microcontroller 10 and the sensors 11, 12 form a digital signal processing block 13 which is preferably an electronic assembly of standard mice. For example, the COP800 type microcontroller from the company NATIONAL SEMICONDUCTOR was used.

The modulated square signals are filtered by a bandpass filter 14 whose central frequency is that of the subcarrier P1, P2 and with a bandwidth equal to 2400 Hz. The resulting signal is applied to an amplifier 15 which drives a transmitting diode in the infrared 16. The diode used is a reference diode SFH415-T, from the company SIEMENS, whose emission power at 950 nm is between 25 and 50 mW per steradian.

The assembly comprising the oscillator 6, the divider 8, the filter, 14, the amplifier 15 and the infrared diode 16 constitutes an emission block 17 which is preferably attached to a standard mouse base element 13.

The power supply 18 is another important element of the pointing device. It comprises a solar cell 19 charging a battery 20 via a regulator 21. The different voltages necessary for the circuits are produced by a DC / DC converter 22 from the voltage of the battery 20.

Figure 4 schematically shows the receiver of the signals transmitted by the pointing devices according to the first embodiment of the invention.

The reception unit 23 comprises a photodiode 24 receiving the beams emitted by the pointing devices 3 coupled in alternating current to the input of a current amplifier 25. This amplifier 25 is followed by a second stage 26, and two 27.28 filters for rejection of components at 50 Hz and 100 Hz that may be present in the signal.

The spectral characteristics of the photodiode 24 are adapted to those of the light emitted. A photodiode 24 of the BPW34-F type, from the company SIEMENS, having a maximum sensitivity at 950 nm and provided with an ambient light filter is used. Amplifiers 25, 26 are circuits of the LM13700 type from the company NATIONAL SEMICONDUCTOR which comprise two amplifiers with automatic gain control (AGC).

<img file="MC200048A1_D0007.tif" />

The amplified signals are transmitted to a demultiplexing block 29 constituted by a battery of tone decoders 30 which each produce a logic signal 0 when a signal has a frequency included in their respective passbands.

The logic signals are processed at the level of a digital processing block 31 by a microprocessor 32, one of the parallel ports of which accesses these logic signals stored by a set of flip-flops with 3-state outputs 33. The microprocessor program 32 takes into account the data of registers 34, representative of a selection of pointing devices and of an operating mode, to develop the binary signals transmitted by means of a line amplifier 35 to the communication port. 5 of the central unit 1. Since the line amplifier 35 is bidirectional, the microprocessor also receives data frames transmitted by the central unit 1, in particular its internal pointing device (ball or other), or an additional mouse connected to an auxiliary port of the housing 4.

The components used are logic circuits in common use. By way of nonlimiting example, the following circuits have been used:

- microprocessor 32: MC68705P3 from MOTOROLA

- 3-state flip-flops 33: DM74LS534 from the company FAIRCHILD

- registers 34: DM74LS374 of the company FAIRCHILD

- line amplifier 35: MAX232 from MAXIM

In this exemplary embodiment, the microprocessor used not comprising a serial communication port, an interface circuit of the asynchronous communication adapter type (ACIA) is implemented (Reference circuit MC6850 from the company MOTOROLA)

In a second embodiment of the internal electronics of each of the pointing devices 3, the generation of the subcarriers P1, P2 is carried out by an entirely digital method. As shown in Figure 5, the transmission block 3 is therefore simplified. The microcontroller 10 comprises, in addition to the program responsible for developing the binary signals representative of the movements and of the state of the mouse, a second program constituting a digital oscillator. The computing power required is significant, evaluated at a few tens of MIPS, but the power supply is limited. A TMS320C54x type circuit from the company TEXAS INSTRUMENTS was therefore chosen for its low consumption (Supply voltage 3.3 V; 0.54 mW / MIPS). The algorithm is described in the various application notes published by this company and will not be repeated here. The samples of the modulated sub-carriers are transmitted to a digital / analog converter 36, then applied to the same elements as in the transmission block 3 of the first embodiment: bandpass filter 14, amplifier 15, infrared diode 16.

In this embodiment, 64 subcarriers are used. The higher frequency exceeds 200 KHz. Shannon's sampling theorem therefore requires a sampling frequency of more than 400 KHz. Given the problem posed by the balance of the power supply, the converter 36 of the AD7524 type from the company ANALOG DEVICES was selected.

Figure 6 also shows that the electronic unit is considerably simplified in this embodiment, since the battery of tone decoders 30 has disappeared. The decoders 30 are replaced by a single analog / digital converter 37 which places the samples of the signals detected on the data bus of the microprocessor 32.

For the same reasons as above, this converter 37 is a fast converter. The suitable model is an AD7822 type circuit from the company ANALOG DEVICE, capable of a maximum sampling rate of 2 MS / s.

The Goertzel algorithm which is used to extract spectral information from the sampled signal is a special case of calculating a discrete Fourier transform, and will not be explained in detail here, since all the explanations are given in the technical note DTMF Tone Generation and Detection: An implementation Using the TMS302C54x (Application Report; SPRA096A- May 2000), published by the company TEXAS INSTRUMENTS, already cited.

According to the indications given in this document, the processing of the 64 channels sampled at 500 kHz uses a computing power close to 200 MIPS.

This second embodiment does not call for any other specific comments, insofar as most of the functions of the electronic unit are performed by software modules from existing libraries, which have been adapted.

The box inside which the electronic elements described above are placed, is presented externally, as shown in FIG. 7, in the form of a console 38. The upper part 39 has a set of 32 switches 40 making it possible to select one or more pointing devices 3 and make the others inoperative. The states of these switches 40 are stored in the registers 34 read by the microprocessor 32. The console 38 also includes a selector for the operating mode of the electronic unit 4. Three basic operating modes are possible:

a first operating mode where a single mouse 3, selected by one of the switches 40, acts on the central unit 1.

- a second operating mode where all the mice act on the same cursor

- a third operating mode where each mouse acts on a cursor which is specific to it.

The basic operating mode chosen is also stored in a register 34, and read back by the microprocessor 32 which launches the appropriate program. In a variant of the second and third modes, the mice 3 which act on the cursor (s) are selected by the switches 40,

The electronic unit 4 comprises a separate part 41 of the console 38 comprising the whole of the reception unit 23. This part 41 is connected by a shielded cable 42 to the console 38, is generally remote from it in operation, but is integral with it if the circumstances are favorable. It in fact comprises a horn antenna 43 intended to collect the beams of infrared light emitted by the mice 3. The collecting horn 43 is placed at a height and arranged so as to cover the entire area where the mice are used 3. The cable 42 ensures the electrical supply of the reception unit 23 and the transmission of the detected signals to the console 38.

As shown in Figure 8, the horn antenna 43 has the general shape of a pyramid trunk with a square base, forming a funnel. A red filter 44 is placed at the inlet. The inner walls 45 are silver and reflect the infrared rays captured towards the photodiode 24. An antenna whose base measures 30 mm X 30 mm, the section at the photodiode 9 mm X 9 mm, and the height is 60 mm has given good results.

Incidentally, this part 41 which contains the horn 43 and the receiving block 23, and follows the shape of the console 38 by extending it when it is integral with it, comprises a housing 46 for housing the folded cable 42.

As already indicated, the aim of this control system for a computer system is to offer a new means of collective training in micro-computer techniques.

An appropriate computer system using the control device according to the invention is shown in Figures 9 and 10, without this example being limiting.

This system includes:

- a laptop 1 under WINDOWS ®

- an LCD tablet 47 connected to the video output of computer 1

an overhead projector 48 of the type commonly used for projection of transparencies

a screen 49 on which the image of the screen of the microcomputer 1 is projected

Q

The communication port 50 of the electronic unit 4 is connected to the mouse port 5 (generally C0M1) of the microcomputer. An additional mouse 51 is connected to the auxiliary port 52 of the housing 4, if the ball 53 of the microcomputer 1 cannot be used. The part 41 containing the reception horn 43 is placed so as to best pick up the signals transmitted by the mice 3.

An LCD tablet 47 with a resolution of 800 X 600 dots (SVGA) usable with a projector 48 of high brightness is preferable.

Under the control of the trainer, the people handling the mice 3 learn to move a cursor 54, and to use the various application software installed on the system 1.

In a graphical environment, the use of the keyboard is quite limited; however, the trainer can display the image of a keyboard at the bottom of the screen 49. Designating the image of a key with a cursor simulates the corresponding keystroke. This is achieved using specific software specific to the operating system.

The normal use of the control device according to the invention seems to be the first mode of operation in which each person has successively the possibility of acting on a single cursor 54, because this corresponds to the usual rule of speaking in group. However, educational projects could take advantage of the third mode of operation of the device, where each person has their own cursor 54, provided that the application software is suitable or suitable.

It goes without saying that the invention is not limited to the above embodiments, given by way of example; on the contrary, it embraces all possible variants of embodiments.