WO1989000442A1

WO1989000442A1 - Electric monitoring of surfaces, in particular the boundary surfaces of sports grounds

Info

Publication number: WO1989000442A1
Application number: PCT/DE1988/000411
Authority: WO
Inventors: Wolfgang Hentschel; Peter Czwalina; Volkmar Meyer
Original assignee: Wolfgang Hentschel; Peter Czwalina; Volkmar Meyer
Priority date: 1987-07-10
Filing date: 1988-07-04
Publication date: 1989-01-26
Also published as: AU1995288A; EP0323987A1; DE3722843A1; DE3722843C2

Abstract

Electronic monitoring of surfaces, in particular the boundary surfaces of sports grounds, is effected by means of surfaces superimposed at a distance apart in the monitoring region, at least one of which is flexible. When an object impinges on the contact surfaces, electrical contact is established between the surfaces and an electric and/or acoustic signal is generated. One contact surface is a resistor surface having constant surface resistance and the other contact surface is a conductive surface. A supply voltage is applied to at least two ends of the resistor surface through a corresponding dropping resistor. For the duration of contact between the contact surfaces, at least two voltage distributors are provided the voltages of which are proportional to the distance between the region of contact and the ends of the resistance path. Since each voltage corresponds to a definite point of impact, it is possible to determine when a ball overshoots a sports ground boundary line as well as the exact position of the ball.

Description

Electronic monitoring of areas, especially the boundaries of playing fields

The invention relates to electronic monitoring of surfaces, in particular the boundary surfaces of playing fields. It initially relates to a method for determining the location of the impact of an object on a surface and, secondly, to a device for determining this location.

A preferred field of application of the invention is the automatic, electronic monitoring of field boundary lines, for example in tennis. As a rule, the lines are monitored by a large number of line judges, especially in the case of highly doped tournaments. Their work is extremely demanding and monitoring requires a considerable amount of staff. It is known from the international tennis championships of England in Wimbledon to electronically monitor the service line. This is done there with the help of a light barrier. This indirectly monitors the surroundings of the service line, which means that monitoring with millimeter precision is not possible. The resulting false alarm cannot be ruled out and leads to considerable confusion among the line and referees and causes considerable disruption to the players. The light barrier technology is only possible with the service line. Monitoring eg the baseline using the same means would lead to an alarm being triggered every time the player gets into the light barrier, which is of course only possible with a serve.

Several possibilities have already been shown in the prior art for monitoring playing field boundary lines for "good" or "off". A somewhat abstruse idea according to DE-OS 34 40 325 provides for the ball to be covered with an elastic metal layer, a conductor network or an electrically conductive plastic or a conductor (wire) in the surface coating, e.g. incorporate the felt layer of the ball and use this prepared ball to bridge or short-circuit separate conductor tracks made of metal or electrically conductive plastic. Theoretically, with such a device, an electrical and / or acoustic signal can be triggered when the ball hits the off zone, but it is forbidden in practice to use balls that differ in their properties from those previously used. Apart from this, the screening of the conductor tracks should not be able to be carried out so finely that all errors - and only such - are reported with certainty.

DE-OS 25 27 465 provides conductors embedded in the floor behind the line to be monitored in each case, which are separated from one another by layers, for example by an air gap. In the event of an impact of the play equipment (ball), the upper layer of the ladder is against the underlying position pressed, whereby a signal can be triggered. DE-OS 32 41 468 also suggests such monitoring and uses strip-shaped signaling elements for this purpose, which are laid in the "off" area along the lines to be monitored and consist of hollow plastic profiles in which metal foils are arranged spaced apart as contact foils and are electrically conductively contacted when an object hits.

With the devices and methods according to DE-OS 25 27 465 and DE-OS 32 41 468, it is possible with some accuracy to optically and / or acoustically identify a ball hitting the "off". However, it is not possible to determine the location of the impact as such, i.e. the distance from the corner of the field to the point of impact behind the baseline. However, this is an essential prerequisite for the monitoring method to function even if the player himself enters the area to be monitored at the same time or at a short distance that is no longer perceptible to the eye, and thus incorrectly simulates an "out" of the ball.

The invention is based on a method according to the preamble of claim 1, as has become known for example from DE-OS 25 27 465 or DE-OS 32 41 468. It is based on the task of proposing a simple method with which it is possible in all or almost all cases that occur is to monitor all mirror lines with sufficient security and accuracy even if several impact events take place simultaneously or with the least delay. For example, it should be possible, in particular, to correctly identify a ball as "good" that strikes near an "off" line within the field while the player is entering the "off" zone. It should also be possible to recognize a ball as "out", even though the player is also in the monitored "out" area. This is not even possible with the previously known methods.

The invention solves this problem in the first place and essentially by the method specified in claim 1, which is essentially characterized in that one of the contact surfaces is formed as a resistance surface with constant surface resistance and the other contact surface as a conductor surface, that one has at least two ends the resistor area is supplied with a supply voltage via a series resistor and receives at least two voltage dividers during the contacting of the contact areas, the voltage values of which are proportional to the respective distance of the contacting zone from the ends of the resistance track.

Advantageous further refinements of this method are specified in subclaims 2 to 8. If you imagine a contact surface arrangement as being a small distance behind the field line and parallel to this strip, the length of which corresponds to the field line, for example, the spaced contact surfaces keep the circuit open until the object comes into contact with the resistance surface and the resistance surface touches the conductor surface. The resistance area, for example with a resistance of 750 Ω / m, is now divided into two sections. This creates two voltage dividers, the tap voltages of which are proportional to the distance from the point of impact to the respective end of the strip. The two measured voltage values therefore allow a statement about the corresponding distances of the point of impact from the two ends of the contact surface arrangement. It can therefore be stated, for example, that the ball hit the "Aus" at a distance of 2.5 m from the left corner of the baseline.

If two impact events now occur in the same area to be monitored, for example the ball strikes next to the player standing in the monitored "off" area, two voltage dividers again arise, the area bridged by short circuit between player and ball failing for the measurement. First of all, it can be used to determine the distance from one of the two corners of the field and the distance from the other end to the other impact event. But - and that is particularly important for the invention, statements can also be made about where the game room and where the ball made the signaling contact between the contact surfaces.

Measurements have shown that, depending on the floor covering and the strength of the players, a tennis ball shows a dwell time of approximately 2 to 20 ms upon impact, which also increases with increasing impact speed due to the compressibility of the ball. However, a player now touches the area to be monitored as a rule for a much longer period of time. If a shorter one is registered at the same time during this longer contacting time, it can be stated with certainty that the ball has consequently been "out".

As will be explained in more detail later in the description of exemplary embodiments, a distinction is still possible even if the player also gets into this zone while the game is hitting the “off” zone to be monitored, but his foot bruises very briefly due to bruising puts.

Every relevant field line can be monitored according to the described procedure. Since the meaning of the lines changes during the course of a game - for example, only the T-line of the opposite field is only important when serving, the parallel side lines either for the single game or for the double game - the connections and disconnections of the lines concerned must be carried out accordingly. The light barrier to monitor the service line in Wimbledon is only switched on when a player prepares to serve. If the surcharge continues the game, the sensor device must be switched off again in order to avoid irrelevant messages during the game.

The method initially assumes that - as in the prior art according to DE-OS 25 27 465 and 32 41 468 - the contact surfaces are to be arranged at a short distance behind each relevant field boundary line. This means that there is still an uncertainty factor with regard to the exact "off" / "good" statement. Because this arrangement does not take into account that, depending on the speed of impact of the ball, it compresses to a greater or lesser extent and thus produces an imprint that is smaller or larger in diameter. A ball landing in the "off" area with a high impact speed and thus actuating the contact surfaces can produce such a large impression that it still touches the field line, that is to say it would still be considered "good" even though an "off" is already reported .

According to a further embodiment of the method according to the invention, this source of error can be completely eliminated if one proceeds in accordance with claim 5. If the "good" zone has been contacted despite simultaneous touching of the "off" zone, the ball can correctly be classified as "good". This facility ge also allows monitoring of violations upon service. The logical connection is to be made in such a way that if the player enters the "good" area in addition to the "off" area, this must be interpreted as a mistake.

The method described and discussed so far is excellently suited for monitoring field lines. With the help of the method characterized in more detail in claim 2, however, any surface can be monitored without gaps, namely with three imageable voltage dividers for a singular impact event and with four voltage dividers even for two simultaneous impact events. As will be explained further below, it is hereby e.g. possible, with throwing, shooting and others a game wall or the like. determining the exact meeting point and including digital and / or analogue as well as acoustically.

The invention is best understood from the following description of its essential and particularly advantageous

Process and device features based on the

Drawings. The drawings show:

1 shows a schematic arrangement and electrical wiring of a pair of contact surfaces,

2 shows the arrangement according to FIG. 1 in the case of a singular contact of the contact surfaces, 3 shows a voltage-time diagram belonging to FIG. 2,

4 shows a representation corresponding to FIG. 2 with double contact,

5 shows a voltage-time diagram for FIG. 4,

6 shows the diagram due to a different touch situation,

7 shows a schematic cross section through a sensor having the contact surfaces,

8 shows a schematic arrangement of the sensor according to FIG. 7 below a surface,

9 shows an alternative arrangement to FIG. 8,

10 is a schematic plan view of a resistance surface arrangement in which the one surface is divided into two partial surfaces,

11 shows the impact of a "good" ball on an arrangement according to FIG. 10,

12 shows the impact of an "off" ball on the arrangement according to FIG. 10,

13 is a schematic representation of a foot defect when crossing the line,

14 is a schematic block diagram representation of the electronic monitoring, Fig. 15 is a schematic representation of a screen display and

Fig. 16 is a schematic representation of an electronic area monitoring.

1 and 2, 10 denotes a first contact surface and 11 denotes a second contact surface. The length L of the contact surface arrangement 10/11 essentially corresponds to the length of a line to be monitored, in particular a field line. If a playing field is mentioned below, the explanations relate to monitoring the lines of a tennis court. Of course, the invention is not limited to this. With it, it is possible to precisely monitor all lines of all known playing fields or other lines. An interesting further possibility can be realized, for example, in the monitoring of the jump zone in ski jumping. Since only width information is to be evaluated here, an equally simple solution can be considered, in which the supply voltages would have to be connected to a contact surface arrangement below the minimum jump distance typical of the hill and on the other outside the conceivable hill record mark. Of course you can also cross border lines e.g. monitor in athletics (start line, long jump bar or similar).

In the exemplary embodiment, the contact surface arrangement 10/11 is viewed from above as Stripes formed. This strip is intended to be arranged at a short distance in the "off" area adjacent to the field line to be monitored.

The contact surface 10 is a resistance surface with constant surface resistance, more precisely with constant resistance per running meter in direction L. As a numerical example, it should be mentioned that the resistance surface 10 can have a resistance of approximately 750 Ω / m.

As can be seen from FIG. 1, both ends of the strip-shaped resistance surface or resistance track 10 are each supplied with a supply voltage U ₁ or U ₂ . This application takes place with the respective interposition of a series resistor R ₁ or R ₂ .

in the simplest possible case, assume that U ₁ = U ₂ and is, for example, 12V. The series resistors R ₁ and R ₂ are preferably constantly adjustable (for example, adjustable). This does not have to be the case, however, since the method also functions exactly when the resistors R ₁ and R _{2 are} variable, but the currents in question are kept constant.

R _L (FIG. 2) denotes the total resistance of the resistance track 10. For example, if the length L corresponds to just under 11 m analogous to the baseline length of a double tennis court of 10.97 m, the total resistance is approx. R _L 8.25 k Ω. The contact surface 11 is conductive and connected to ground (U _O = OV) in the exemplary embodiment. If there is contact between the contact surfaces 1 and 2, two voltage dividers arise, the respective partial voltages U _X1 and U _X2 between the points A and C or B and C can be tapped. The point of contact (contact point in FIG. 2) divides the contact surface arrangement into two sections with the length L ₁ and the length L ₂ . The total ohm 'see resistance of the resistance surface or path 10 therefore results

(1) R _L = R _L1 + R _L2.

The following therefore applies to the partial resistors R _L1 and R _L2 :

(2) R _L1 = R _L.

(3) R _L2 = R _L.

The partial voltage U _X1 that can be tapped results from

(4) U _X1 = R _L1

to

(5) U _X1 = (U ₁ -U ₀ ).

and accordingly

(6) U _X2 = (U ₂ -U ₀ ).

From (5) and (6) it can be seen that, provided that U ₁ , U ₀ , R ₁ and R _{2 are} constant, the tensions U _X1 and U _X2 which can be tapped are proportional to the respective partial lengths L ₁ and L ₂ . With the preferred setting of the series resistors R ₁ and R ₂ with 1/2 R _{L the} following simplifications

(7) U _X1 = U ₁ .

(8) U _X2 = U ₂ .

If the contact takes place at the left end of the contact surface arrangement 10/11 with respect to FIG. 1, L ₁ = O and L ₂ = L. In this case, the following result:

(9) U _X1 = U ₁ . = Φ

and (10) U _X2 = U ₂

The extreme values for U _X1 and U _X2 behave accordingly if the point of contact is at the other end of the contact surface arrangement 10/11.

In the example selected, the partial voltage U _X1 and UX ₂ tapped in each case can only be between O and 2/3 U ₁ . or fluctuate between O and 2/3 U ₂ . These are the basic parameters between which "something happens" in the event of an impact event. U _X1 = U ₁ and U _X2 = U ₂ are only in the idle state.

As can be seen from the dependence of the tapped partial voltages U _X1 and U _X2 on the respective length L ₁ and L ₂ , the effective voltage values can be used to determine the distance from one and / or the other end of the line to be monitored Object hit on this.

If the duration of the impact event is monitored - cf. here the schematic Fig. 3 - can also make a statement about whether a ball and / or a player has touched the line. In the case of FIG. 3, the voltage-time curve when a ball hits is shown. This touches the contact surface arrangement 10/11 and at a time t ₁ it leaves again after a period of time Δ t at time t ₂ . The partial voltages U _X1 and U _X2 that occur when touched are indicated qualitatively in the diagram. The absolute values U _X1 and U _X2 allow an immediate conclusion to be drawn about the location of the touch, while the time period of the touch Δ t gives a distinction between the impact of the ball or a player. In experiments it was found that the dwell time of a tennis ball, depending on its impact energy and / or surface quality, is of the order of about 2 to 20 ms. If an impact dwell time Δt is found within this range, it can therefore be said with great certainty that the player has not touched the area or line to be monitored, since the dwell time of his foot on the ground is generally much longer.

Now, however, in the course of a game, at the time of a "good" / "off" decision, the ball and player can hit or kick the "off" field at the same time. Such a double event is shown schematically in FIG. 4. The contact point 1 there marks the zone of the ball contact, the contact point 2 that of the player location. The distance of the first point of contact from the adjacent line end is denoted by L ₁ , that of the second point of contact 2 from the end assigned to it by L ₂ and the short-circuit length by L ₃ . With reference to FIG. 5, in this example the player would enter the contact surface arrangement at time t ₁ and again at time t ₄ leave. If he is standing calmly on the line, he turns from t ₁ to t. the constant partial voltages U _X2 and U _X1 . The absolute values are of course location-dependent. If the ball also hits the contact surface arrangement and the situation shown in FIG. 4 results, the relationship decreases

(11) R _L = R _{L1 +} R _{LK +} R _L2

the resistance R _L on the respective side for the duration Δ t of the ball contact. According to (5), the partial voltage U _X1 drops accordingly, to an absolute value corresponding to the length L ₁ . Due to the significantly shorter time period Δ t of the ball dwell time compared to the dwell time of the player (t ₄ - t ₁ ), the fact of touching the ball can be determined and localized despite simultaneous contact surface contact on the part of the player.

In Fig. 6 a special case is shown, which differs from that shown in FIG. 5 in that the player is not standing still on the contact surface arrangement 10/11, but bounces with his foot there, i.e. the contact surface arrangement is constantly loaded and in rapid change relieved again. Such bouncing can occur especially when sliding ("rubbing the floor").

The voltage impulses that initially only arise from the bouncing are shown in FIG. 6 posed; they never fall below the U _X1 min or U _X2 min typical for the location during the time period t ₄ - t ₁ . If the ball now strikes at the point of contact 1 on the left of the player with respect to FIG. 5, the previous length (L ₁ + L ₃ ) changes to L ₁ for the measurement, thus reducing in any case. According to (5), this leads to a sudden drop in the partial voltage U _X1 for the ball dwell time Δ t. Thus, despite the simultaneous player behavior on the ground, the fact of touching the ball and the location of the ball hitting can be determined based on the voltage curve of U _X1 .

In the basic version of the method and its device according to the invention, it is assumed, in particular for simpler versions, that a strip-shaped contact surface arrangement 10/11 is arranged in the "off" region of a line to be monitored at a close distance from it. However, this still results in a certain geometric uncertainty, which depends in particular on the impact energy with which the ball touches the field line in the sense of "good" and / or alternatively or at the same time also the sensor marking the "off". In order to achieve objective results here, the resistance track 10 is divided into two strips 10, 10 '(resistance track 1 and resistance track 2) which are parallel to one another - FIG. 10. The resistance track 1 is laid congruent with the field line, the resistance track 2 at a short distance of eg 1-2 cm next to it in the "off". The two strips 10, 10 'can have a common conductor track 11 be highlighted. However, both the resistance path 1 and the resistance path 2 are each connected in the manner described, in particular according to FIG. 1. In this way it can be determined whether the ball has touched the resistance track 1 and / or the resistance track 2. Since every minimal touch on the field line is rated as "good" by the rules, but an "off" is reported when the ball hits resistance track 2 at the same time, one can achieve here by logical connection that if the ball according to Fig 4 has touched only or also the resistance track 1 ("good"), the error avoidance to be expected per se is suppressed by impact on the resistance track 2 ("off").

Only if the ball does not contact the resistance track 1 ("good") according to FIG. 5 does the ball count as "out".

In an analog application, you can also monitor a foot fault when serving by using the appropriate logical link. A foot fault in tennis is considered to be one if the player touches the field line with his foot. A logical link would have to be carried out here, which then reports an error if the player touches resistance path 1 ("good") or only.

Of course, since the meaning of the individual field lines are different during a complete game cycle, appropriate switching, for example by the referee to make. Only in this respect does this correspond to the state of the art.

For a possible specific implementation of the contact surface arrangements 10/11 per playing field line, reference is made to FIG. 7 by way of example. It shows the cross section of a sensor 12 consisting of a lower elastic film or also rigid plate 13, a conductor track 14 applied thereon, e.g. made of conductive silver, an upper, flexible carrier film 15 and a layer attached underneath this made of a material forming an ohmic resistance, e.g. Graphite. The two sub-assemblies 13, 14 on the one hand and 15/16 on the other hand are kept at a short distance with the help of spacers 17, 17 ', which ensure that there is no pressure on the film

15 there is no contact between the tracks 16 and 14 (corresponding to the contact surfaces 10 and 11). The spacers 17 are preferably themselves elastic, so that they provide the information desired in the event of an object impacting, in particular the upper arrangement 15,

16 do not offer any significant resistance. The supports 13 and 15 can be screen printed with the required materials such as conductive silver, graphite or the like. print. This is known per se from membrane keyboards.

The embodiment described above, in which two resistance tracks 10, 10 'are provided parallel to one another, can be imagined with respect to FIG. 7 in cross-section, for example, modified so that one over the Ab den designated 17' The resistance track 16 interrupts the longitudinal path and extends the spacer 17 'accordingly up to the film 15. The galvanically separated two contact surfaces 10 and 10 'then arise and thus a "double sensor strip".

To protect against external influences, in particular against moisture, it is provided that the contact surface arrangement (sensor) is encased by an insulating plastic 18 (FIGS. 8 and 9). Of course, the encapsulation should not impair the desired flexible behavior of the sensor.

In Fig. 8, 19 is a carpet or a plastic covering, under which the arrangement is attached.

in Fig. 9. with 20, for example, an out-line typical of the playing field, below which the arrangement is attached.

Of course there are a variety of other options. Part 10 'of the contact surface arrangement (sensor) can itself be designed as a playing field boundary line and can hold a surface which is adapted to the space. In the case of plastic coverings, the sensor arrangement can also be inserted or the like in pockets prepared in the floor. be or, for example, be incorporated into the floor during weaving or tufting. 14 schematically illustrates the electronic evaluation of each line using a "double sensor strip". Two double voltage controls must be evaluated for each line to be monitored. Line 1 is thus assigned two arrangements A ₁ and B ₁ approximately corresponding to FIG. 1, line 2 two analog arrangements A ₂ and B ₂ etc.

An A / D converter is assigned to each voltage tap U _X1 , U _X2 for each contact surface pair, which feeds the digitized values to an evaluation processor. If 8-bit A / D converters are involved, each line can be "rasterized" in 256 steps. The longest line of the tennis court, the side line of 23.77 m, should therefore be measured in a grid of 10 cm accuracy along the line. All evaluation processors are coordinated by a coordination processor, which can display the evaluated signals on a screen, for example.

Such a screen display could be designed according to FIG. 15. A tennis court with its characteristic lines is shown on the screen. If a ball hits a contact surface arrangement, it can be displayed with a point or another symbol according to location. The player touching the sensor is also displayed as such on the screen. With the help of a suitable image memory, this currently occurring phenomenon can be viewed for a longer period Record the time period and / or record it on data storage devices such as video tapes.

When playing tennis or other field games, line crossings are monitored. The invention therefore serves to monitor the crossing of such lines. Nevertheless, the monitoring takes place in a finally wide strip along the line. The stripe should be so wide that the referee's eye will unequivocally recognize that the ball has crossed the sensor in the "off" direction, which can no longer be displayed. Despite the line monitoring, the sensor is therefore very well designed after registration.

Not only can the invention be used to monitor the crossing of lines within relatively narrow band zones, but also the impact of an object over a larger area. For example, imagine a throwing game in which a ball is thrown against a wall surface, but is not held there but bounces back. In order to signal such contacts, according to the invention, at least three ends, corners or edge zones of the resistance surface can be supplied with a supply voltage U ₁ to U ₃ via a series resistor R ₁ to R ₃ , so that at least three are kept during the contacting of the contact surfaces Receives voltage divider whose voltage values U _X1 to U _{X3 are} proportional to the respective distance of the contacting zone from the connections of the supply voltages U ₁ to U ₃ . With such a triple arrangement, the geometric position of a singular impact event can be determined exactly. If the case occurs that two objects hit the surface to be monitored at the same time and both events are to be identified independently of one another, it is expedient to extend the triple arrangement to a quadruple arrangement, as shown in FIG. 16. The dependencies of the tapped partial voltages U _X1 to U _X4 between the respective contact point and the feed points can be seen from the simple formulas contained on the drawing sheet in FIG. 16.

The contact areas are dimensioned according to the (play) area.

Claims

Claims:

1.Method for determining the location of the impact of an object on a surface, in particular for monitoring the crossing of boundary lines such as playing field lines, using contact surfaces connected to a supply voltage, which are kept at a distance from one another in the monitoring zone, and at least the upper one of which is flexible, the contact surfaces coming into contact with an object when they strike an object and thereby giving an electrical and / or acoustic signal, characterized in that one of the contact surfaces is formed as a resistance surface with constant surface resistance and the other contact surface as a conductor surface that At least two ends of the resistance surface are each supplied with a supply voltage via a series resistor and receive at least two voltage dividers during the contacting of the contact surfaces, the voltage values of which are proportional to the respective are hasty distance of the contacting zone from the ends of the resistance track.

2. The method according to claim 1, characterized in that one or at least three ends

Edge zones of the resistive surface are each supplied with a supply voltage via a series resistor and at least three span during the contacting of the contact surfaces receives voltage dividers whose voltage values are proportional to the respective distance of the contacting zone from the connections of the supply voltages.

3. The method according to claim 1 or 2, characterized in that the time duration of the contacting of the contact surfaces is evaluated.

4. The method according to claim 1 or 2, characterized in that the time duration of the contact (s) of the contact surfaces is evaluated and related to the value of the voltage (s) tapped due to the contact (s).

5. The method according to any one of the preceding claims, characterized in that the resistance surface and / or the conductor surface in the longitudinal direction of the zone to be monitored is divided into two mutually parallel, closely spaced strips, one of which corresponds essentially to the width of the line to be monitored, Is congruent to this and its other, preferably wider, is arranged on the "off" side of the line to be monitored, that each strip can form at least two voltage dividers, which are monitored for the coincidence of impact events in terms of location and duration.

6. The method according to any one of the preceding claims, characterized in that each of the contact surface arrangements to be monitored Line ozw. Zone assigns an A / D converter and an evaluation processor for each voltage tap and supplies the digital output values of all evaluation processors to at least one coordination processor.

7. The method according to any one of the preceding claims, characterized in that the location of the contacting of the contact surfaces is displayed on a screen in flat geometrically similar illustration.

8. The method according to any one of the preceding claims, characterized in that one fixes the size of the respective series resistor with about half the total resistance of the resistance surface.

9.Device for determining the location of an object hitting an area, in particular for monitoring the crossing of boundary lines such as playing field lines, with a sensor consisting of contact areas connected to a supply voltage, the contact areas in the monitoring zone being kept one above the other at a distance from them at least the upper one is flexible, the contact surfaces coming into electrically conductive contact when an object strikes and thereby giving an electrical and / or acoustic signal, characterized in that at least one contact surface (16) on a flexible carrier (15), in particular a plastic film is upset that the distance is more upright holding spacers (17, 17 ') made of insulating material are small in cross section and elastically flexible.

10. The device according to claim 9, characterized in that the sensor (12) is surrounded by a particularly moisture-tight, elastic sheath (18), in particular based on plastic.

11. The device according to claim 9 or 10, characterized in that the sensor (12) is strip-shaped and is applied to or embedded on or immediately below the area to be monitored on the surface.

12. The apparatus according to claim 9 or one of the following, characterized in that the surface is provided with guide grooves for inserting the sensor (12).

13. The apparatus of claim 9 or one of the following, characterized in that the sensor (12) is formed by treating its face itself as a boundary line.

14. The apparatus according to claim 9 or one of the following, characterized in that the sensor

(12) structured, in particular by coating its visible surface, having a property corresponding to the surface to be equipped with regard to elasticity and coefficient of friction.

15. The apparatus according to claim 9 or one of the following, characterized in that the sensor (12) is incorporated into this in the manufacture of the surface to be equipped.