EP0125624B1 - Device for the electromagnetic transmission of an event in a disturbed environment - Google Patents

Abstract

The electromagnetic transmission in an interference-laden environment of events defined by the time of their occurrence is accomplished by repeatedly generating, at equal intervals after occurrence of the event, signals representing the occurrence of the event. An event which must be defined by the time te at which it occurs triggers a switch which in turn triggers a time base whose signal is sent to a counter. The counter produces at its output a sequence of pulses which are coded in a coder. The code indicates for each pulse the deviation in time DELTA Ti which separates it from the time at which the event occurred. The sequence of pulses is sent electromagnetically to a receiver via a transmitter. The first interference-free pulse received is processed by a decoder which provides the value DELTA Ti to an arithmetic unit. The arithmetic unit subtracts the value DELTA Ti from the time of day th to obtain the time of day te of the event. The device is applicable in particular to the timing of sporting events.

Description

The invention relates to a device for transmitting electromagnetically in a disturbed environment a sporting event comprising in particular the start of a race, said event being defined by the time t _{e at} which it occurred, device comprising a transmitting means capable of transmitting a train of pulses consecutive to said event, each of the pulses of said train being assigned a distinctive sign making it possible to locate it in time (ΔT) with respect to said event, and a receiving means capable of detecting the first undisturbed pulse of said train which, in consideration of the time th existing at the time of this detection, makes it possible to restore the value of the time t _{e at} which said event occurred.

When it comes to transmitting, during sports races for example, events occurring in various decentralized places towards a central place of management, there are generally two known means: cable transmission or transmission by channel electromagnetic.

An example of the first case is exposed in patent CH 621 915 where peripheral organs are connected via an electronic module to a central organ for controlling the operation and exploitation of information via a cable. common and unique two-wire. The idea expressed in the cited patent makes it possible to avoid heavy and very expensive wiring, especially in flying installations. However, in the case where a large distance separates the events to be measured from the central place of management - ski or orienteering races for example - it may be advantageous to transmit said events by electromagnetic means (radio waves, light or infrared). This avoids having to lay long lines otherwise exposed to accidental cuts. Even in a circuit taking place in a relatively narrow circle, such a system can be advantageous since it eliminates a whole time of preparation and storage.

The transmission of sporting events by electromagnetic means is known from US patent ― A ― 3,651,507. In this document, the start of the race is given by an audible signal, a whistle for example, which simultaneously actuates a transmitter. The signal from the transmitter is received by a receiver with an antenna and a clock-driven display system.

The radio link, known from the document cited above, does not, however, have only advantages. It is particularly affected by disturbances which can be significant enough to prevent the safe transmission of events. We are thinking here particularly of atmospheric disturbances or those caused by neighboring transmitters. Such disturbances can prevent the transmission of an event that occurs only once. It will be understood that if this event is characterized for example by the time of arrival of a runner, as found in sports timing, this time will be irretrievably lost.

To overcome this difficulty, it has been proposed to repeat several times the sending of the message and this long enough to be sure of its reception. In the case where this message essentially contains the time at which the event occurs, we will repeat this time five, ten or twenty times, this value always remaining the same. If by time, we mean here the time given by a mother clock - which can be set to the time of day given by the speaking clock for example - located at the place where the event takes place, it will be necessary to have an extremely precise time base if you want to be able, in a sports race, to decide between the competitors. In fact, the time taken to cover a given distance is deduced from the difference between the time of departure and the time of arrival. It follows that each of the departure and arrival stations must be equipped with very precise clocks, if necessary synchronized with each other.

We can fix ideas by an example. The lapse of time between the start of the first runner and the finish of the last runner is two hours for a given competition. During these two hours it is desired that the time given by the clock of the departure station and the time given by the clock of the arrival station do not diverge by more than one thousandth of a second. Under these conditions, the precision required of each of the clocks will be 0.001. 24/2 = 0.012 seconds per day. Such precision can only be achieved by means of a sophisticated and expensive device which, moreover, will have to be stabilized in temperature from -20 ° C to + 60 ° C.

Author's certificate SU-A-183 413 proposes to improve the safety of radio transmission of the firing instant of a charge used in seismic research. The system is based on the transmission of signals triggered by the load and coded in series, the coding changing every second. Thus, as soon as one of the signals is received correctly, the instant of ignition can be evaluated.

Apart from the fact that this document does not mention the use of such a system applied to the timing of sports races, it neither envisages nor suggests that the coded signals are arranged to carry, in addition to the indications locating them. in time in relation to the event, indications making it possible to identify each of the runners who take part in the competition. Furthermore, if we refer to the last paragraph of column 1 of the cited document, we can read that the generator 1 presented in Figure 1 is stabilized by a quartz, which indicates that in this system it is the transmitter which carries the time base and that the receiver does not have it (see also last paragraph of column 3), contrary to what will be described in the present invention where the transmitter is content with an imprecise oscillator and where the receiver carries a precision time base.

When several runners take part simultaneously in the same race, it is necessary to identify them in order to be able to attribute to them the result which is their own. For this, an installation which also uses radio transmission is described in document EP ― A ― 0074330. This installation allows the identification and determination of the instant of passage of a plurality of mobiles at a determined point on their trajectory. In this document, a device is installed on each mobile which includes means for transmitting an identification signal in the form of a code. However, this installation does not offer any means of ensuring safe transmission in an environment which would be disturbed by radio interference.

The present invention proposes to remedy the drawbacks mentioned above by using the means which appear in the claims.

• La figure 1 montre un schéma de principe de l'émetteur d'évènements selon l'invention.
• La figure 2 montre un schéma de principe du récepteur d'évènement émis par l'émetteur de la figure 1.
• La figure 3 est un diagramme qui fait état des impulsions émises par l'émetteur et qui montre comment sont formées lesdites impulsions.
• La figure 4 présente une variante qui indique comment sont transmis plusieurs évènements -à partir du même émetteur.

The invention will now be understood in the light of the following description, given by way of example and illustrated by the drawings in which:

• Figure 1 shows a block diagram of the event transmitter according to the invention.
• Figure 2 shows a block diagram of the event receiver sent by the transmitter of Figure 1.
• FIG. 3 is a diagram which shows the pulses emitted by the transmitter and which shows how said pulses are formed.
• Figure 4 presents a variant which indicates how several events are transmitted - from the same transmitter.

Figure 1 is a block diagram of the transmitter according to the invention. This transmitter is generally located near the event which, when it occurs at the time t _e to be determined, closes the switch 1. There are as many transmitters as measurement points and , in the case of a sports competition, at least the starting line and the finishing line will be fitted with such a device. The switch 1 can be in the form of a light barrier or an electromechanical gate. The electrical pulse emitted by the switch 1 switches the flip-flop 2 which then has a level 1 at its output Q. The AND gate 3 receives on its first input the output signal of a time base 4 and on its second input, the signal from the output Q of the flip-flop 2 so that the signal from the time base 4 can pass the AND gate 3 when the output Q is at level 1. The clock pulses CP in coming from time base 4 and present at the output of the gate AND in turn control a counter 5 which delivers at its output 7 second pulses spaced from each other by predetermined and equal periods T, fixed by the counter 5 Thus these second pulses represent a repetition of the first pulse, triggered by the event, and are defined in time by the intervals ΔT ₁ , ΔT ₂ , ... ΔT _i , ... ΔT _n which separate them from the first impulse.

In a practical example, the frequency of the time base was chosen at 10 kHz. The first of the second pulses following the first trigger pulse is spaced from the latter by one tenth of a second. The second pulses are also spaced apart from one tenth of a second. In this case, the counter 5 will transmit on its output 7 a pulse out of 1000 received at its input CP. Thus, in this example, the event which occurred when the switch 1 was closed will be repeated every tenth of a second. As experience shows that a per-. electromagnetic turbation lasts only a few tenths of a second, we can think that during a transmission which lasts one second, at least one of the ten pulses emitted will be taken into account by the receiver. Also, in the example chosen, the transmitter 5 will produce, after having sent ten pulses, a reset command by line 6 which will act on the counter itself and on the flip-flop 2. As a result, the Q output will go to zero and block the AND gate 3.

The diagram in Figure 3 explains graphically how is organized what has been described above. The signals of the time base 4 are represented on line 9 ′ of the diagram. The event closing the switch 1 is represented by the rising edge of the pulse 8 shown in line 10 of the diagram. At this moment, the output Q of the flip-flop goes to state 1 and remains there for a predetermined period T _e , as shown in line 11 of the diagram. The pulses of time base 4 then pass the AND gate 3 and are represented on line 12. The pulses of line 12 and the state 1 of the output Q of the flip-flop 2 shown on line 11 are maintained until 'at the arrival of the rising edge of the pulse 16 (shown in line 13) which is the reset signal from line 6 of Figure 1. These pulses attack the counter 5 which is arranged to not produce on its output 7 only some of these 15 at predetermined and equal periods T, to obtain in the end T _e = n · T _i as shown in line 14.

As we suppose the transmission channel affected by noise, it is clear that on reception of the signal from line 14, one or more pulses 15 will be missed so that the receiver will be unable to discern whether the first pulse received is that occurring at ΔT ₁ or AT ₂ or even AT, after the signal emitted by the event. It is therefore necessary to assign each of the pulses 15 with a distinctive sign enabling the. situate time in relation to the event. This assignment is implemented by the coder 20 represented in FIG. 1. This coder will for example provide a serial number for each pulse 15 received at its input, serial number coded in binary. This is done very simply by means of a divider by ten containing four flip-flops which give their outputs a parallel binary code available on four wires. The encoder 20 also comprises a UART (universal asynchronous receivertransmitter) circuit, for example of the RCA 1854 type, which transforms the parallel coded signal received from the divider by ten into a signal coded in series. Thus, thanks to this system, the identification of each pulse makes it possible to know which time interval AT, separates it from the rising edge of the first pulse 8 caused by the event. There is therefore available at the output of the encoder 20 not only the pulse train 15 but AT intervals, which will allow, as will be seen later, to allocate a time t _e to the event which has just occurred. It is pointed out that other systems could be chosen to distinguish between them each of the pulses 15. For example, one could have a different width for each of the pulses or else assign them each with a different low frequency signal.

The transmitter device of FIG. 1 is further supplemented by a transmitter system 21, the carrier of which is radiated by the antenna 23. It will be noted that the carrier will generally be located in bands extending from 180 to 470 MHz or even in the " citizen-band "(27 MHz). The carrier of the transmitter is modulated by the signal from the encoder 20.

We have insisted so far on the transmission of events at least defined by the times at which they occur. It could however be that we want to take advantage of this transmission to add to the pulses sent other data such as for example the bib number of a runner and the place where this same runner is located (start, intermediate station, arrival). It is therefore possible, in addition, to add an addressing device 24 which can be a key keyboard whose data is then transmitted to the encoder 20.

Figure 2 is a block diagram of the event receiver emitted by the transmitter which has been discussed in connection with Figure 1. The electromagnetic waves are picked up by the antenna 25 and the receiver itself 26 which brings to its output 36 a demodulated signal. this signal is introduced into a decoder 27 which, on the one hand, selects from among all the signals received the first undisturbed pulse (and therefore carrying complete information) and, on the other hand, assigns to said pulse a value of OT interval, in response to the distinguishing sign it bears. This value is transmitted to an arithmetic unit 30 by the line 29. The decoder 27 can be a UART circuit of the same type as that already mentioned with respect to the encoder 20. In addition, arrangements are made to prevent the transmission of other values intervals which could follow the first value considered as valid. The same arithmetic unit 30 receives by line 28 the signal from a master clock 35 giving for example the current time of day th, Knowing now at what time of day t ,, the time interval OT, has been transmitted, we can calculate the time of day t _e at which the event occurred by performing the subtraction using the arithmetic unit 30:

A first important advantage can be drawn from the device which has just been described: that of ensuring perfect security for the transmission of the event which, it should be remembered, takes place only once. Thus, the repetition of the data resulting from the event will allow at least one of the transmitted pulses to reach the receiver, pulse which once decoded will indicate precisely the time of day of the event.

A second no less important advantage lies in the use of much less sophisticated and therefore much cheaper materials, as will be explained now.

Contrary to what was mentioned in the preamble where it was envisaged to transmit the time of day directly from clocks placed at the place of the event, we have just described a system which, according to the invention, implements a only precise clock located at the receiving station for all events from peripheral sending stations. Here, each of the transmitting stations is equipped with a time base which need not be very precise.

To take an example, we will use as time base 4 (see Figure 1) a simple non-thermocompensated quartz oscillator. Such an oscillator is very inexpensive and its drift is of the order of 100 seconds / day. However, in an example cited above, it has been explained that the transmission time of an event can last approximately one second. If during one day (86,400 seconds) the oscillator drift is 100 seconds, this same drift will only be 100 / 86,400, or 0.0012 seconds over the considered period of 1 second. Thus, if the first valid pulse received by the receiver is the tenth of a train of pulses each spaced by a tenth of a second, the error made will not exceed one thousandth of a second. This error will of course decrease if the pulse taken into account precedes the tenth pulse.

It is therefore clear that the repeated transmission of an event by means of pulses bearing the reference to the difference which separates them from the event itself not only ensures safe transmission but also authorizes the use of inexpensive equipment. If the use of such a device is particularly welcome for the timing of sporting events, it is obvious that it can be envisaged whenever it acts to identify in time an event whatever it is .

It should also be mentioned that during the predetermined period T _E (FIG. 3), it would be possible to transmit several events instead of just one. This situation appears in Figure 4. Here events 31, 32 and 33 are repeated in the same way as described above. To avoid possible overlaps, we arrange to offset the repetition pulses relative to each other. In the example shown in the graph, it is obvious that if we did not take precautions and if we repeated all three events every tenth of a second the second repetition of event 32 (= 32 ") would coincide with the first repetition of event 33 (= 33 '). To remedy this drawback, event 33 was repeated for the first time only 0.125 seconds after its advent This naturally requires additional coding and decoding but which presents no difficulty if one follows the general idea stated according to the present invention.

Claims (5)

1. Arrangement for electromagnetically transmitting in a disturbed environment a sporting event (8) including in particular the start of a race, said event being defined by the time t_e at which it occurs, said arrangement including a transmitting means adapted to transmit a pulse train (15) following said event, each of the pulses of said train being attributed a distinctive sign enabling it to be situated in time (ΔT_i) relative to said event, and a receiving means adapted to detect the first undisturbed pulse of said train which by virtue of the time th of the moment of said detection enables restoring the value of the time t_e at which said event occurred, characterized by the fact that the transmitting means includes a sensor (1) adapted to generate a first electrical pulse (8) triggered by said event, a low precision time base (4), said time base being triggered by said first pulse, a counter (5) adapted to count the signals emitted by the time base so as to produce during a first predetermined period (T_e) second electrical pulses (15) separated from one another by second predetermined equal periods (T_i), an encoder (20) for attributing to each of said second pulses at least one distinctive sign, in particular a serial number, in accordance with the interval (ΔT_i,) which separates them from said first pulse, and a transmitter (21) for transmitting electromagnetic waves modulated by the output signal from said encoder, and that the receiving means includes a receiver (26) for receiving said electromagnetic waves; a decoder (27) arranged to select the first non disturbed pulse. from said second pulses received by the receiver and assigning to it a time interval value (ΔT_i) corresponding to the distinctive sign attributed thereto, a clock (35) adapted to give the time (t_h) with high precision and an arithmetic unit (30) for performing the subtraction _th -ΔT_i = ^te _.

2. Arrangement according to claim 1 characterized by the fact that the precision of the time base (4) is better than 100 seconds per 24 hours.

3. Arrangement according to claim 1 characterized by the fact that the first predetermined period (T_E) during which the second pulses are produced lasts 1 second and that the second equal predetermined periods (T,) which separate said second pulses from one another last 0.1 second.

4. Arrangement according to claim 1 characterized by the fact that the time t_h given by the clock (35) is the time of day.

5. Arrangement according to claim 1 characterized by the fact that each of the second pulses (15) of said train is further assigned a code enabling the identification of each of the competitors engaged in the race in response to an addressing device (24) borne by the transmitting means and that said decoder (27) borne by the receiving means further comprises means for identifying the competitor to which said time t_e pertains.

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