EP1774358A1

EP1774358A1 - High-capacity surveillance system

Info

Publication number: EP1774358A1
Application number: EP05790896A
Authority: EP
Inventors: Frédéric Aberlenc
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-07-20
Filing date: 2005-07-20
Publication date: 2007-04-18
Also published as: US20090140917A1; WO2006018509A1; FR2873520A1; FR2873520B1

Abstract

The invention relates to a surveillance system wherein a localisation terminal TL and a surveillance terminal co-operate. Each terminal TL comprises: means for the acquisition R1 L of a localisation message; communication means MRL-ARL adapted to a communication channel; and control means MCL for connecting the acquisition means and the communication means in response to an activation signal. Furthermore, the activation signal coincides with a pre-determined interval of a repetitive frame of said communication channel.

Description

High capacity monitoring system

The present invention relates to a monitoring system with high capacity.

The field of the invention is in particular that of the surveillance of persons. We naturally think of a hiker or mountaineer who is in distress, whether lost or injured, for example.

In such a situation, the position of that person, the entity to be monitored, should be communicated to a third party such as a parent or friend, who is supervising, so that the third party can initiate a search procedure. A known surveillance system uses two point-to-point radio terminals each coupled to a "GPS" receiver. The term GPS (Global Positioning System) refers to a constellation of satellites that broadcasts signals allowing the receiver to obtain its spatial coordinates. The entity to be monitored has a location terminal provided for communicating a location message in which its position is acquired by means of its GPS receiver. The supervising entity has a monitoring terminal provided to receive this location message in order to acquire the position of the location terminal. In the United States of America, this system allows communication via channels reserved for amateur radio or "CB" ("CB" for the abbreviation of "Citizen Band"). Thus, by using "FRS" (Family Radio Services) channels in the 460 MHz UHF band, the range reaches 3 kilometers. These channels are obviously limited in number, but if they are all occupied, the entity to be monitored no longer has the means to report its position to the entity that monitors.

The invention thus relates to a monitoring system that offers increased capacity. According to the invention, a location terminal comprises:

means for acquiring a location message,

communication means adapted to a communication channel,

control means for connecting these acquisition means and these communication means in response to an activation signal;

SPir -

IS OR C ^Q fcπ & MA in addition, the activation signal coincides with a predetermined time interval of a repetitive frame of this communication channel.

It follows that the communication channel is able to support either a single location terminal but a number of terminals corresponding to the number of time slots that includes the frame.

Preferably, this terminal comprises means for positioning this predetermined time interval in the frame.

According to an additional characteristic of the invention, this frame comprising a first sub-frame composed of allocated time slots, and a second sub-frame composed of priority time slots, the predetermined time interval is a time interval. allocated.

The second sub-frame is intended to handle emergency situations.

Indeed, advantageously, the two subframes are nested.

By way of example, the frame which has a duration of 30 seconds has 30 allocated time slots of 500 ms and 30 priority time slots of 500 ms.

In the location terminal:

the acquisition means follow identification means which receive a reception signal emanating from a positioning system, and

the communication means are radio transmission means. On the other hand, the location message includes information relating to the position of the terminal.

Optionally, this location message also includes information relating to the identification of this terminal.

Furthermore, the reception signal comprising synchronization information, the terminal comprises means for producing the activation signal in response to this synchronization information.

When the frame comprises two sub-frames, the terminal preferably comprises means for, in response to an alarm signal, also producing the activation signal at least in the nth priority time slot following the appearance of this alarm signal (n being a predetermined number) and it comprises means for introducing an alarm word into the location message. It is therefore not necessary to wait for the next allocated time slot of the terminal that can occur in the worst case 30 seconds after the appearance of an alarm signal before transmitting the alarm word.

It is then desirable for the terminal to include means for repeating this alarm word in the first allocated time slot following the nth priority time slot.

According to the invention, just like the location terminal, a monitoring terminal comprises:

means for acquiring a location message; communication means adapted to a communication channel;

control means for connecting these acquisition means and these communication means in response to an activation signal; in addition, the activation signal coincides with a predetermined time interval of a repetitive frame of this communication channel, this frame being synchronized to a clock signal. In this monitoring terminal:

the acquisition means consist of a memory, and the communication means are reception means.

According to a first option, the location message comprising identification information, the reception means operating uninterruptedly, this terminal comprises another memory in which is stored an identification value, the activation signal being produced by the user. coordination body in case of identity between the identification information and the identification value.

According to a second option, the activation signal coincides with a predetermined time interval of a repetitive frame synchronized to a clock signal. In this case, the monitoring terminal comprises means for positioning this predetermined time interval in the frame.

Whichever option is chosen, according to a preferred embodiment, the terminal comprises determination means for producing a situation message in response to a reception signal emanating from a positioning system. R2005 / 001875

Here again, the reception signal comprising synchronization information, the terminal comprises means for producing the activation signal in response to this synchronization information.

Thus, the location message comprising position information, the situation message comprising location information, this terminal comprises means for calculating the distance between this position and this location.

Then, the monitoring terminal produces an alert signal if this distance exceeds a first predetermined threshold, this distance being a first measurement.

It follows that the supervising entity has no operation to perform to be alerted of an unexpected departure from the entity to be monitored. The parent of the child can fall asleep quietly on the beach because if his child goes too far, he will be informed. Likewise, the monitoring terminal produces an alert signal if the speed of displacement of the position exceeds a second predetermined threshold, this speed being a second measurement.

Advantageously, the terminal comprises means for displaying at least one of these two measurements. Preferably, the monitoring terminal comprising a compass, it also comprises a servo module of the display means on this compass.

In addition, the monitoring terminal includes means for indicating the direction in which the entity to be monitored is located. When the frame comprises two sub-frames, the location message comprising an alarm word, the monitoring terminal comprises means for also producing the activation signal in response to this alarm word.

Then, the monitoring terminal comprises means for producing an alert signal in response to this alarm word. In addition, the monitoring terminal includes means for identifying a free allocated time slot, which allows synchronization of the location terminal.

The present invention will now appear in greater detail in the context of the following description of an exemplary embodiment given by way of illustration with reference to the appended figures which represent:

FIG. 1, a diagram of a location terminal, and - Figure 2, a diagram of a monitoring terminal.

In the context of wireless communications, the frequency spectrum is a precious commodity, so that it is subject to strict regulation. Thus, this spectrum is distributed among many applications such as radio, television, amateur radio, point-to-point communications between two terminals (walkie-talkies for example), wireless telephony, mobile telephony, links satellite communication systems, radio guidance and remote controls of various devices, not to mention military applications. All these applications are subject to administrative authorization.

For example, in the United States of America, the "FRS" system includes 14 channels in the 460 MHz UHF band. This type of direct communication at short distance makes it possible to overcome the heavy networks of the GSM type. In addition to the above applications, it frequently happens that at least one narrow-band channel is free-use subject to certain conditions such as:

- maximum transmission power,

- maximum bandwidth width,

- time use quota. For example, in France, we can freely use the so-called

"869 - 500 mW band" of 869 MHz center frequency. In reality, this channel extends from 869.40 MHz to 869.65 MHz.

The invention consists in realizing time multiplexing on any one of these channels at a rate of 1,200 bits / second, for example. Thus, a frame is defined in which the messages transiting between a location terminal and the monitoring terminal attached to it are inserted.

Briefly, a frame is subdivided into a plurality of time slots each corresponding to a subchannel. Each subchannel is able to support unidirectional communication between two terminals. In order to be able to identify the sub-channel allocated to them, these terminals must have a common time reference or, in other words, they must synchronize on the frame.

Several known techniques can synchronize a terminal on the other. They will not be more detailed because they are part of the state of the art. Another technique consists in synchronizing the two terminals independently on a time signal which constitutes a common reference. We think in the first place of the GPS system which delivers a universal time whose precision is of the order of the nanosecond. This precision is considerable and it goes without saying that it is amply sufficient for the implementation of the invention.

According to a preferred embodiment, the frame comprises several subframes, two in the present case. By convention, the first sub-frame is composed of a set of allocated time slots and the second sub-frame of a set of priority time slots.

Specifically, the frame has a duration of 30 seconds and has 60 timeslot of 500 milliseconds. The two subframes each have 30 time slots. The first sub-frame gathers the time slots that occupy an odd rank in the frame and the second sub-frame gathers those that occupy an even rank in that frame. It thus appears that the two subframes are nested, the justification of this arrangement being explained later.

Referring to Figure 1, a location terminal TL is provided to obtain its geographical position in one way or another, that is to say its spatial coordinates or at least planar. In this case, use is made of the "GPS" positioning system and the terminal therefore comprises locating means in the form of an AGL "GPS" antenna coupled to a "GPS" MGL receiver.

These locating means AGL, MGL are connected to a control member such as an MCL microcontroller with its SWL application software. Acquisition means, a RAM which can be reduced to a first register R1L in this case, are filled by the microcontroller MCL which provides them with a location message. This message essentially comprises position information relating to the position of the terminal TL representing its coordinates in any referential, for example its latitude, longitude and possibly its altitude.

This first register R1L is used to transmit the location message. Details on this transmission operation are given later. The location message also includes identification information relating to the identification of the location terminal TL which is stored for example in a read-only memory type "ROM" (for the English expression "Read OnIy Memory"), a second register R2L in this case.

Given the transmission rate of 1200 bits / second and the duration of a time interval which is 500 milliseconds, the maximum capacity of the first register R1 L will be equal to the product of these two values, ie 600 bits.

In practice, we take a 40-bit safety margin to adopt a 560-bit register whose content is commonly referred to as a burst of emission.

Classically, this salvo comprises: - possibly a section of header,

- possibly a synchronization word,

- necessarily a body,

- possibly a terminal section.

The synchronization word may be required when the two terminals that exchange this burst are not synchronized frequently or temporally on an external common reference.

The salvo body contains the useful information, that which is the object of the transmission, and it thus contains the message of localization.

The localization terminal TL also comprises communication means. These are transmission means granted on the communication channel, associating an MRL radio transmitter and an ARL transmitting antenna. The transmitter is also connected to the MCL microcontroller.

It further comprises control means, which means may be incorporated in the microcontroller MCL, for connecting the acquisition means R1L to the radio transmitter MRL in response to an activation signal. Thus, this activation signal triggers the emission of the burst.

This activation signal may come from any device, for example pressing a dedicated key location terminal. It may also come from a coordinating organ possibly integrated in the microcontroller MCL, as explained below.

The terminal TL also comprises a CPL counter whose capacity is equal to the number of time slots of the frame, 60 in this case. This counter is incremented by a clock signal from a time base BTL which delivers a peak at each change of time interval, every 500 milliseconds in this case. It therefore indicates the sequence number in the frame of the current time interval. The time base BTL is here synchronized on the receiver "GPS" MGL. We can also provide a periodic reset of the CPL counter to prevent possible drift of the latter.

The location terminal TL also has a third register R3L for synchronizing the burst emission. This register R3L is advantageously a programmable and erasable memory of the type

"EEPROM" (for the English expression "Electrically Erasable PROgrammable"

Memory "). It identifies the sequence number in the frame of the time slot allocated to the terminal. The activation signal is produced by the coordination member in case of identity between the current value of the counter CPL and the value recorded in the third register R3L. In the present case, a logic gate LGL carrying out the AND logic function of these two values is used.

The third register R3L is initialized with an initialization value permanently stored in the terminal TL. This value can even be marked on the box of this terminal so that it is easily known. The contents of this register R3L is possibly modified by means of a BRL adjustment button whose mode of action will be detailed later.

The different elements of the location terminal TL are electrically powered by a battery BAL possibly connected to an internal charger CIL.

Thus, the transmission of the location message is periodically triggered in the same time interval of the successive frames automatically without any intervention.

At the same time, the TL location terminal is designed to handle emergency situations.

A first alarm signal comes from a DIL immersion detector which produces it for the MCL microcontroller. This detector is activated when the terminal TL is immersed, following a fall in a pool or the accidental crossing of the rail of a ship for example. A second alarm signal is issued from an emergency button BUL also connected to the microcontroller MCL. This button can be operated by the TL terminal holder in different circumstances:

- proven or potential aggression,

- malaise, - panic,

- impossibility to find his way. A third alarm signal comes from a CDL shock detector such as an accelerometer which also produces it for the MCL microcontroller. An abnormal situation is thus identified, whether the terminal has fallen alone or that it has been dragged by a fall from the one to which it is attached. Following the generation of any alarm signal, the microcontroller

MCL introduces in the location message an alarm word such as "SOS" and the identification of the terminal TL (stored in the second register).

This alarm word may take the place of the position information in the location message or it may be reserved a location identified in this message.

It is furthermore desirable to specify the nature of the situation which has caused the production of this alarm signal. Thus, in the case of respective appearance of the first, second or third alarm signal, the alarm word includes the respective information "WATER", "CRISE" or "SHOCK". The location terminal TL has a fourth register R4L initialized at a value that does not identify a time interval (an integer greater than 60 in this case). This register is also advantageously also a programmable and erasable memory which, at the appearance of any alarm signal, is loaded by the sum modulo 60 of the double of the integer part of half of the current value of the counter CPL and an offset value of 2n where n is any positive integer. It is not modified until it is reset, this reset can be triggered in particular by the appearance of the activation signal or by a delay. The fourth register R4L thus identifies a priority time slot of the second sub-frame, the nth following the current time interval.

The microcontroller MCL is also programmed to produce the activation signal in case of identity between the current value of the counter CPL and the value recorded in the fourth register R4L.

This ensures a fast transmission of the alarm word, in the next priority time slot if n is 1. It is not necessary to wait for the next allocated time slot of the terminal TL that can occur in the worst case 30 seconds after the appearance of an alarm signal. The reason why the two subframes are nested is now clearly established. It is also preferable to repeat the alarm word in one or more priority time intervals following that during which its first transmission has occurred.

It should also be noted that, if the microcontroller MCL does not modify the location message, this alarm word will also be repeated in the next allocated time slot of the terminal TL.

The arrangement of the sub-frames adopted so far leaves an important place at the priority time intervals. To increase the number of location terminals that can simultaneously use the communication channel, the size of the second sub-frame can be reduced by stipulating, for example, that it comprises the time slots whose rank in the frame is a multiple of 4 .

With reference to FIG. 2, a monitoring terminal TS also comprises communication means. These are reception means here, associating an MRS radio receiver and an ARS receiving antenna tuned to the communication channel. The MRS receiver is also connected to a control organ such as an MCS microcontroller with its SWS application software.

This terminal also comprises acquisition means which here take the form of a first memory M1S reception which is a random access memory.

It further comprises control means, which means may be incorporated in the microcontroller MCS, for connecting these acquisition means M1S to the radio receiver MRS in response to an activation signal.

It further comprises a CPS counter whose capacity is equal to the number of time slots of the frame, 60 in this case. This counter is incremented by a clock signal from a time base BTS which delivers a peak at each change of time interval, every 500 milliseconds in this case. It therefore indicates the sequence number in the frame of the current time interval. Like the location terminal TL, the monitoring terminal TS receives from the positioning system "GPS" a reception signal via determination means in the form of an AGS "GPS" antenna coupled to a GPS receiver MGS.

These determination means AGS, MGS are connected to the microcontroller MCS. A second memory M2S live can be reduced to a register is filled by the microcontroller MCS which provides a status message. This message essentially comprises location information relating to the geographical location of the monitoring terminal TS representing its coordinates in any referential, for example its latitude, longitude and possibly its altitude. The time base BTS is here synchronized on the receiver "GPS"

AMS. We can also provide a periodic reset of the CPS counter to prevent possible drift of the latter.

The monitoring terminal TS also has a third memory M3S for synchronizing the reception of a salvo. This third memory M3S identifies the sequence number in the frame of the time slot allocated to a location terminal.

According to a first mode of synchronization, the activation signal is produced by a coordination element in case of identity between the current value of the counter CPS and the value recorded in the third memory M3S. In the present case, an LGS logic gate carrying out the AND logic function of these two values is used.

The initialization of this memory is done with the initialization value of the third register R3L of the location terminal TL.

However, when this location terminal is put into service, it may be that this initialization value corresponds to a time interval of the frame which is already occupied.

It is therefore desirable to identify by means of the MRS radio receiver of the monitoring terminal TS which allocated time slots are available in the channel to retain one of these, the first for example, to visualize it in any way and load it into the third M3S memory. This identification can be practiced conventionally by performing a measurement of the level received in these time intervals.

It should now be clarified that the modification of the content of the third register R3L of the location terminal TL is done by means of the adjustment button BRL to naturally retain the time interval identified in the third memory M3S of the monitoring terminal TS.

For this purpose, a parameterization mode of the location terminal TL is provided.

By way of example, this terminal TL being provided with a light-emitting diode, a first pressing on the adjustment button BRL initiates a temporary flashing of the diode and simultaneously triggers a delay. Pressing this button again before the timer has elapsed puts the terminal in parameter mode. In the event that the button is not pressed while this timer is running, the terminal automatically switches to "normal operation" mode. In parameter mode, pressing this BRL button increments the contents of the third R3L register by two.

According to a first option, a display device may be provided on the location terminal TL to display the contents of its third register R3L. According to a second option, it can be expected that when the location terminal TL is put into service, it transmits at very low power, being arranged in the immediate vicinity of the monitoring terminal TS. The location terminal TL places an initialization word in the location message. It is then necessary to manipulate the BRL adjustment button until the monitoring terminal TS has recognized this initialization word. This second option makes it possible to deport the indication of the synchronization of the two terminals of the location terminal TL to the monitoring terminal TS. In this case, the display device of the location terminal TL is no longer necessary.

To exit the parameterization mode, it provides for any safe manipulation of the BRL adjustment button, such as two successive presses intervening in a short period of time or a single support of a relatively long duration.

The different elements of the monitoring terminal TS are electrically powered by a battery BAS possibly connected to an internal charger CIS.

In the monitoring terminal TS, the activation signal is also produced during all the priority time slots of the second sub-frame.

According to a second mode of synchronization of the monitoring terminal TS, the latter also listens to all the allocated time slots of the first sub-frame.

In this case, the third memory M3S is loaded by an identification value which is not the time slot allocated to the localization terminal TL but the identification of this terminal TL. Naturally, this terminal TL will have previously placed in the location message identification information that appears in its second register R2L. The activation signal is then produced by the coordination member in case of identity between the identification information and the identification value recorded in the third memory M3S.

The invention thus leaves the choice between two modes of synchronization of the monitoring terminal TS. It would also apply, of course, with another mode of synchronization that is not described.

The acquisition of the location message is thus triggered, periodically in the same time interval of the first successive sub-frames, and continuously during the second sub-frame, this automatically without any intervention.

If no alarm signal has been generated by the location terminal TL, a new location message from it is available at each new frame in the monitoring terminal TS through the microcontroller MCS. This microcontroller MCS extracts, on the one hand from the location message, the position information and, on the other hand, from the location message, the location information. It includes means for calculating the distance between this position and this location.

If this distance exceeds a first predetermined threshold, the monitoring terminal TS produces a first warning signal SUS in light, acoustic or vibratory form.

Similarly, if the traveling speed of the position of the locating terminal TL exceeds a second predetermined threshold, the monitoring terminal TS produces a second alert signal SVS similar to the first alert signal SUS. The two thresholds mentioned above can be introduced into the monitoring terminal TS by means of any human-machine interface such as a keyboard.

Moreover, this terminal TS comprises display means, for example an EVS display screen which is connected to the microcontroller MCS. If the latter can access an SNS navigation system, it is then possible to move a base map on this screen EVS to display by a point or a cross the position of the location terminal TL and possibly a vector speed.

Preferably, the monitoring terminal TS also comprises a CES compass and a servo module (not shown) of the means for EVS visualization. Thus, the orientation of the card is independent of the position of the terminal TS.

It is also possible to provide on the monitoring terminal TS the indication of the direction in which the location terminal TL is located. This indication appears for example at the periphery of the EVS screen or on another display means. It can also take the form of an arrow superimposed on the base map in the center of which is the TS monitoring terminal.

In addition, the distance separating the two terminals TL, TS is displayed. The same goes for the north. If, on the other hand, an alarm signal has been generated by the location terminal TL, a new location message from this terminal is available in the monitoring terminal TS as soon as it has been sent. Indeed, its microcontroller MCS listens to all the time slots of the second sub-frame. This microcontroller MCS comprises means for recognizing the identification of the location terminal TL in the location message and, after that, extracting the alarm word to communicate its meaning in any visual and / or sound way and or vibratory.

Advantageously, the monitoring terminal TS is able to follow several location terminals. The means to implement to do this are within the reach of the skilled person since it is substantially a duplication. They will not be more detailed. It will be specified simply that this terminal TS has identifications of all the location terminals that it supports. The information relating to these different terminals can be displayed either successively or concomitantly provided that each terminal is identified by a distinctive graphic sign or by a particular color.

The embodiment of the invention presented above was chosen in view of its concrete nature. It would not be possible, however, to exhaustively list all the embodiments covered by this invention. In particular, any means described may be replaced by equivalent means without departing from the scope of the present invention.

Claims

1) TL terminal, TS comprising:

acquisition means R1 L, M1 S of a location message, MRL-ARL, MRS-ARS communication means adapted to a communication channel,

control means MCL, MCS for connecting said acquisition means and said communication means in response to an activation signal, characterized in that said activation signal coincides with a predetermined time interval of a repetitive frame of this communication channel.

2) Terminal according to claim 1, characterized in that it comprises means BRL, MRS for positioning said predetermined time interval in said frame.

3) Terminal according to claim 2, characterized in that said frame comprising a first sub-frame composed of allocated time slots, and a second sub-frame composed of priority time slots, said predetermined time interval is an interval time allowed.

4) Terminal according to claim 3, characterized in that said subframes are nested.

5) Terminal according to any one of claims 1 to 4, characterized in that said frame has a duration of 30 seconds and has 30 allocated time slots of 500 ms and 30 priority time slots of 500 ms.

6) Localization terminal TL according to any one of claims 1 to 5, characterized in that:

said acquisition means R1L succeed to AGL-MGL locating means which receive a reception signal from a positioning system, and in that said communication means are radio transmission means

MRL-ARL.

7) Terminal according to claim 6, characterized in that said location message comprises information relating to the position of said terminal TL.

8) Terminal according to any one of claims 6 or 7, characterized in that said location message comprises information relating to the identification of said terminal TL.

9) Terminal according to any one of claims 6 to 8, characterized in that said reception signal comprising a synchronization information, it comprises means LGL, CPL, R3L for producing said activation signal in response to said information of synchronization.

10) Location terminal according to any one of claims 3 to 5 characterized in that - said acquisition means R1L succeeding AGL-MGL locating means which receive a reception signal from a positioning system, and

said communication means being radio transmission means MRL-ARL, it comprises means MCL, R4L for, in response to an alarm signal, also producing said activation signal at least in the nth priority time slot following the occurrence of said alarm signal, n being a predetermined number, and in that it comprises means MCL for introducing an alarm word in said location message.

11) Terminal according to claim 10, characterized in that it comprises means for repeating said alarm word in the first allocated time slot following said nth priority time slot. 12) TS monitoring terminal according to claim 1, characterized in that:

said acquisition means consist of an M1S memory, and

said communication means are ARS-MRS reception means.

13) Terminal according to claim 12 characterized in that, said location message comprising identification information, said receiving means ARS-MRS operating uninterrupted, it comprises another memory M3S in which is recorded an identification value said activation signal being generated in case of identity between said identification information and said identification value.

14) TS monitoring terminal according to any one of claims 1 to 5, characterized in that:

said acquisition means consist of an M1S memory, and

said communication means are ARS-MRS reception means.

15) Terminal according to any one of claims 12 to 14, characterized in that it comprises AGS-MGS determination means for producing a status message in response to a reception signal from a positioning system.

16) Terminal according to claim 15, characterized in that said reception signal comprising a synchronization information, it comprises means LGS, CPS, M3S for producing said activation signal in response to said synchronization information.

17) Terminal according to any one of claims 15 or 16, characterized in that said location message comprising a position information, said situation message comprising location information, it comprises MCS means for calculating the distance between said position and said location. 18) Terminal according to claim 17, characterized in that it produces an alert signal SUS if said distance exceeds a first predetermined threshold, this distance being a first measurement.

19) Terminal according to claim 17, characterized in that it produces an SVS warning signal if the movement speed of said position exceeds a second predetermined threshold, this speed being a second measurement.

20) Terminal according to any one of claims 18 or 19, characterized in that it comprises EVS display means of said measurement.

21) Terminal according to claim 20, characterized in that comprising a CES compass, it comprises a servo module of said display means EVS on said compass CES.

22) Terminal according to any one of claims 17 to 21, characterized in that it comprises means EVS indication of the direction of said position.

23) TS monitoring terminal according to any one of claims 3 or 4 characterized in that:

said acquisition means consisting of a memory M1S, and said means of communication being reception means

ARS-MRS,

said location message comprising an alarm word, it comprises means MCS for also producing said activation signal in response to this alarm word.

24) Terminal according to claim 23, characterized in that it comprises means for producing a warning signal SUS-SVS in response to said alarm word.

25) Terminal according to any one of claims 3 or 4, characterized in that: said acquisition means consisting of an M1S memory, and said communication means being ARS-MRS receiving means, it comprises means ARS-MRS, MCS for identifying a free allocated time slot.