The invention relates to an object control system com¬ prising a central control unit, a high frequency transmission generator, a control switching unit, a plurality of radiators for high frequency radiation, and a plurality of control units at a distance from the radiators, each control unit being associated with an object to be co trolled. Such object control systems are known in practice.

In such an object control system, high frequency energy is applied from the high frequency transmission generator to a plu- rality of radiators via the control switching unit. These radia¬ tors when being controlled emit high frequency energy to a plu¬ rality of control units being at a distance from the radiators. The high frequency radiation received by a control unit when ex¬ ceeding the detection threshold will cause a reaction in the control unit, whereupon this unit will implement its pre-instruc- ted task.

A problem which occurs often in practice is the cross talk - of high frequency energy between the radiators. This cross talk may occur in the control switching unit or between the radiators due to the fact that the radiators are to close to each other. By a correct positioning of each radiator with respect to the others this last cause of cross talk can be obviated.

A selective object control system is used in order to obtain unambiguous activation and if required to enable an object local- isation. When the maximum available high frequency for a selected radiator'is reduced in the central control switching unit due to cross talk or for another reason so that a portion of the high frequency signal energy lands in other radiators, an activation of a control unit being opposite to a non-selected radiator will take place in dependency of the distance.

Such a cross talk may be avoided by using a completely unam¬ biguous selecting control switching unit or by observing an unsafe area around each radiator. Said last measure in many cases is not useful especially when the control units are movable.

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The degree of cross talk is dependent on the amount of high frequency energy applied from the high frequency transmission generator via the control switching unit which amount is depen¬ dent on the power setting of the high-frequency transmission gene rator. The activation distance, that .means the distance to the radiator, in which the control unit may be activated by the in¬ coming signal upon exceeding its detection threshold, depends on the power setting of the high frequency transmission genera¬ tor. The cross talk us§.y occurs during the switching operation in the control switching unit as it is difficult to switch high- frequency energy. Only with the aid of a complicated and bulky control switching unit a complete decoupling of the selected radia tor with respect to the other non-selected radiators may be ob¬ tained with the aid for example of coaxial switches. The invention aims at providing an object control system which includes a very simple and compact control switching unit by which a complete unambiguous controlling operation and a cer¬ tain controlling distance is obtained while using the maximum admissable high-frequency energy. This aim in accordance with the invention is obtained with an object control system of the above mentioned type by providing the high frequency transmission generator with an adjustable power setting, and providing each control unit with an adjustable detection sensitivity; whereby each radiator has a disconnecting member; and whereby the control switching unit in its switching operation in combination with the disconnecting members of the radiators is embodied such that high frequency energy is only applied at one time in essence to only one selected radiator, hile the disconnecting operation of the disconnecting member associate with this radiator is ended and the non-selected radiators are choked by the maintained disconnecting operation of their discon¬ necting members.

In the implementation according to the invention of the object control system the high frequency energy being applied by cross talk in the control switching unit to a non-selected radiator, therefore is lead away by the choking operation of the associated disconnecting member and will not be emitted.

With the aid of the invention each radiator in case it is not selected, may be damped or choked. -For choking a non-' selected radiator use is made of the principle that each well functioning radiator is tuned to a certain frequency, and said radiator will not function or badly when being detuned.

In an advantageous embodiment according to the invention the control switching unit is a very compact and simple high frequency multiplexer which applies the high frequency signal to the selected radiators, whereby each radiator includes an energy transmission coil and a tuning coil with an adjusting element functioning as the disconnecting member, and whereby each control unit at least includes a receiving coil, a detection circuit being adjusted such that the control unit only within controlling distance to the selected radiator is enabled by its high frequency radiation, and a reaction circuit. The adjusting element of the tuning coil may be controlled from the multiplexer by a control voltage which is applied via a separate conductor or which is derived from the high frequency signal. Thereto the radiator for the activation of the adjusting element may have a supply source, like a lithium cell, which is switched by the control voltage. Hereby the adjusting element may be a voltage controlled capacitor or a capacitor which can be adjusted with the aid of an electronic or mechanical contact.

In an advantageous embodiment the radiator comprises a bar of ferrite. In a further advantageous embodiment each control unit includes also a power supply, such as a lithium cell, which is connected in the control unit such that the detection circuit is fed continuously and the reaction circuit is only fed during a reaction period following the exceeding of the detection switching threshold by the high frequency signal.

The object control system may be used for the control of a production and/or regulation process, in which the objects asso-

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ciated and connected with the control units are implemented as operating and/or controlling members of the process.

The object control system may also be used as an identific¬ ation system for the identification of objects, such as living beings or things or articles, whereby the system additionally is provided with a receiving- and decoding circuit, whereby in each control unit the reaction circuit comprises a transmission cir¬ cuit having a transmission coil and coding element which circuit upon being excited via the detection circuit supplies a code signal and whereby the control of the adjusting element of the tuning coil is such that the selected radiator upon activation by the high frequency signal is choked only after a period which is sufficient for the receipt on of the code signal. Such an identification system may be used advantageously for the identification of lifestock, such as cows in a stable, whereby the high frequency transmission generator is embodied and adjusted such that the high frequency power supplied to the radiator equals 200 W, and that the detection circuit in the control unit with its sensitivety is embodied to a continuous current drain of 1 - 1.5 /uA, such that the activation distance is 1 or 2 meters. In this case the relay associated with the mechanical contact of the adjusting element may be embodied such that it drops off with a delay. Also the central control unit may be embodied as a central processing unit. The invention will be explained more in detail with referenc to the drawings, in which:

-Pig. 1 shows a schematical diagram of the object control system according to the invention;

-Pig. 2 shows a schematical display of the unsafe zone associated with a radiator without disconnection member in case the radiator is not selected, and of the activation distance in case the radiator indeed is selected;

Fig. 3 shows a schematic view of the radiator according to the invention; and Fig. 4 shows a diagram of an embodiment of a control unit.

In Fig. 1 the object control system comprises a highfrequen cy transmission generator 1 , areceiving and decoding circuit _j

a central control unit 10, a control switching unit 2, a radiator 3 for high frequency radiation, a control or activation unit 4 associated with the object to be controled and being at some dis¬ tance with respect to the radiator 3 - The transmission generator 1 for example includes a ^~ 0 MHz oscillator which supplies impulses of 1 - 20 msec.

In such an object contπol system the avoidance of cross talk between the radiators is of major importance in orde to ^' obtain a system insensitive '"to disturbances and having the largest possible adjustable activation distance also by employing a construction, as compact as possible and simple and cheap technical means. -By positioning the radiators mutually in the correct manner cross talk from one radiator directly to another may be avoided.

An important source of cross talk however is the control

• _j c switching unit 2, in which the high frequency power of the trans¬ mission generator 1 under control of the central control unit 10 is tranferred via the switch to a selected radiator. Only with the aid of an expensive implementation of the control switching unit, such as for example with the aid of coaxial and alsobully switches

20 this may be realized.Ξoweverwhen a technically simple and compact control switching unit is applied one will have to accepta certain degree of cross talk in the switch, whereby this high frequency cross talk energy however in no case may initiate a undesired ac¬ tivation of an non-selected control unit. One requires a selective

25 object control system for obtaining an unambiguous activation and if required an object localization.

When the object switching unit is /Sufficiently decoupled and the non-selected radiator is not choked or insufficiently, a port¬ ion of the energy destined for the selected radiator will land

30 on a non-selected radiator and will be emitted. By this the ^•" activation may take place of the control unit being opposite a non-selected radiator. Such a undesired activation of a non-se¬ lected control unit may be avoided by observing an unsafe zone at each radiator. In Fig. 2 an unsafe zone a and a desired ac-

35 tivation distance b is indicated for an arbitrary radiator. By reason of the high frequency cross talk energy applied to a non-

^^Λy ^~

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selected radiator a control unit being in the unsafe zone may also be activated. The magnitude of the unsafe zone dviously is dependent on the adjustment of the high frequency transmissio generator, on the degree of cross talk, and on the detection sensitivety of the control switching unit.

For certain applications, such as for control units asso¬ ciated with stationary objects, it may be workable to* seb an unsaf zone in order to avoid therewith a false activation. However if one has moving objects and therefore also moving control units, the object has to stay at such a distance from the radiator that the control unit will never enter the unsafe zone. In many cases however this cannot be , guaranteed in practice.

By taking care in accordance with the invention that the hi frequency cross talk energy applied to a non-selected radiator i choked or damped at the radiator, an unsafe zone may be avoided. By damping a non-selected radiator independent of the amoun of applied cross talk energy one attends to that this radiator does not emit energy based on the principle that eachwell functio ing radiator is tuned to a certain frequency. By adjusting this tuning the radiator cannot or hardly emit any energy.

Fig. 3 shows an example of a radiator according to the in¬ vention, which comprises a bar of ferrite on which an energy transmission coil having a supply lead 6 and a tuning coil 7 is mounted. The tuning coil 7 is also tuned with the aid of the ad- justing element 8 which for e --ample may comprise a variable capac tor.

By a correct tuning of the tuning coil a selected radiator may emit the high frequency energy supplied to it in a maximum manner. The desadjustment or detuning in case of non-selection m be realized by changing the number of windings of the tuning coi by changing the location of the tuning coil with respect to the energy trasmissiDn coil, or by changes in the adjusting element by which the tuning coil obtains a choking effect. Of these posibi- lities a change in the adjusting dement technically is the most simple one.

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The adjusting element may be implemented as a voltage control¬ led capacitor, or as an adjustable and/or fixed capacitor, which may be adjusted with the aid of an electronic or mechanical con¬ tact of a relay for example. The control of the adjusting may be realized for example by a control voltage which is ap¬ plied via an additional lead or which is derived from the high frequency signal._ or this a supply source, such as a lit-hium cell, may be taken up at the radiator, which source during the period of selection of the radiator may be switched by the control voltage of the additional lead or by the control voltage derived from the high frequency signal or by electromagnetic wireless radiation.

Such a radiator therefore has no unsafe zone in the control system, and may be embodied in a compact and cheap manner. The control units advantageously may be used in a production and/or controlling process, in which the control units after being ac- ^" tivated by their reaction circuit can emit a signal by which in- formation is transmitted. The central control unit 10 may be embodied as a processor..The control unit also may be used for the control of adjusting members, such as valves, switches, etc. The activation distance between radiator and associated con¬ trol unit(s) within which the emitted high frequency radiation may activate the control unit(s) is of great importance for the several possibilities of the system.Because of this activation dis- tance also the number of control units in a certain space is de¬ termined as an unambigeous activation is required at all times.

When one starts from a maximum transmission of 200 mwat ^• according to the instructions^ disturbance insensitive objsct control system may be realized having a activation distance of 1 to 2 meters.

When this distance is sufficient use may be made of a con¬ trol unit which is partially passive, which means that the con¬ tinuous current drain of it is extremely low at a value' of for example 1 to 1.5/uA. This is of great importance for the manner of supply of the control unit, which in many applications for example with moving objects has to be done by its own power

supply. The control unit consists as indicated of a detection circuit having a receiving coil, and a following reaction cir¬ cuit. Such a control unit advantageously may have a power supply such as for example 2 lithium cells which feed the detection circuit continuously -and feed the reaction circuit only during a certain reaction period following the exceeding of the detec¬ tion threshold by the incoming signal. The reaction circuit therefore is switched in at a sufficiently strong input signal, and the circuit switches itself out after the end of the reaction period. Such a supply of these cells for example may function for a period of minimum ten years.

When a larger activation distance is required.,the detection circuit of the control unit may be embodied in a more active man¬ ner or obtaining a larger activation distance in a dis-turbance in- sensitive control system, whereby the current drain of the control unit increases. Such a disturbance insensitive detection circuit at a larger activation distance goes at the expence of the life time of the" power supply and therefore of a sealed compact control unit. By the larger activation distance also the mutual distance between/control units has to be maintained ina better manner in order to avoid that two control units are activated simultaneous¬ ly. Becauseofthe whole system becomes more expensive, more com¬ plicated and vulnerable.

It is of importance to implement the control distance in an adjustable manner by means of the setting of the power of the high frequency transmission generator and/or by adjusting the detection sensitivity in the control unit. Each control unit may obtain a certain detection threshold by reason of the adjustability of the detection sensitivity. The disadvantage is to some degree that the control units, which some time occur in larger numbers than the radiators, then will ^' differ mutually.

The activation distance in a normal system embodiment may be made equal for each combination of radiator-control unit by embo¬ dying the high frequency transmission generator such that it can be adjusted.

In an advantageous embodiment of the control system accord¬ ing to the invention objects may be identified, such as living beings or articles. These articles for example may be moved in a production process or transportation process in accordance with a certain traject. The system advantageously may be also used for the identification of live-stock, such as for example cattle in a stable.

The control unit 3 according to Fig. 4 which is embodied for identification purposes-includes a detection circuit 11 having a receiving coil 12, and a reaction circuit consisting of a coder 13 a d a transmission circuit 14 having an antenna or coil 13« In the coder 13 a coding associated with the certain object, for example a certain cow, is set. After activation a coded signal may be emitted by this reaction ci cuit, which coded signal is received by the associated radiator or a central receiving antenna. In this manner information may be exchanged in the system. When in the system use is made of radiators having an adjusting .element, it means that the radiator during the pe¬ riod of information exchange has to be tuned and should not be choked.

. When control units having passive circuits are used, which means only a continuously switched-in detection circuit and a normally switched-out reaction circuit, whereby a long live time for the internal power supply stays guaranteed, ~-. reasonable strong,; /ϊϊigh frequency signal has to be emitted by the high frequency transmission generator. In this case the advantage is also that for activating the control unit by disturbing signals a relative¬ ly high disturbance level is required,by which also the activat¬ ing distance is limited as the activation power is tied to a limit, such as 200 mwatt.

The activation distance in the control system in most cases is smaller than the distance across which a signal could be re¬ ceived.

In case two or more control units are activated by reason of cross talk via high frequency energy the following now may occur:

The information emitted by the relative control unit and having the largest signal amplitude will then be recognized as the only true information by the receiving- and decoding circuit

9 of the control system. In this state two or more control units will be activated and controled simultaneously, only one of whic is opposite the selected radiator. also

However, a plurality of control units may/be activated si¬ multaneously, of which control units no one is opposite the se¬ lected radiator. The receiver then may receive false information from a conissl unit which is activated by reason of cross talk.

In order to avoid above mentioned problems one has to take care that a control unit in all certainty may only be activated by a selected radiator.

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