DE19811572C1 - Operating method for motor vehicle anti-theft device - Google Patents

Abstract

A method for operating an anti-theft system which includes a transmit-receive unit (34) arranged in the vehicle and which transmits an interrogation signal via at least one of at least two antennae (4,6) arranged at different vehicle points. With reception of the signal, an answer transmitter (24) sends an answer signal which is received by the transmit-receive unit and then compared with a desired value in an evaluation unit (32), in which with a positive comparison obtained, predetermined vehicle functions are activated. A number of interrogation signals are sent by a transmission parameter filed in a control device (8), according to the antennae in use, the power, and the phase angle of the signals transmitted to the antennae, until an answer signal is received. The sequence of the transmission parameter with which the interrogation signals are sent is a fixed preset sequence depending on the operating state of the vehicle.

Description

A known anti-theft system (DE 43 30 118 C1) in antennas arranged on the driver's door. If a user in the motor vehicle wants to get in by pressing ei For example, there is a trigger on the driver's door a question-answer dialog is triggered. In doing so, a Question signal sent by the antennas, that of a from the Be user-worn responder should be received. This sends an encrypted Ant when the query signal is received word signal. In the motor vehicle, the response signal with a expected target signal compared and with a positive comparison (successful authentication) the doors are unlocked.

It is known to lower the antennas in the motor vehicle as two right-angled loop antennas formed. By To control the two antennas with sinusoidal signals generated electromagnetic fields. These fields induce in a coil of the responder has a voltage. So that span voltage is as large as possible, the field lines must satisfy the coil enforce appropriately.

It may happen that the responder positions this is that the winding area of its coil is parallel to the field lines of the transmitted magnetic field. The question signal is then not received or received only insufficiently. Not only for the proper function of the anti-theft system is a Safe dialogue with the respondent is required. Also from  For security reasons, it is important that this dialogue take place det, for example when routine during vehicle operation moderately asked for the existence of a valid responder becomes. If the responder is not found, this leads to appropriately configured anti-theft systems that the vehicle must be stopped after a warning, because certain vehicle functions are blocked.

In order to avoid the problems described above, DE 197 18 764 C1, of which in the preambles of the attached Claims are made, proposed a plurality of question signals, which are reflected in a control unit put transmission parameters, such as the antenna used in each case ne, the power or the phase position of the antennas Differentiated signals are sent until an answer signal is received. This ensures that the necessary dialogue between the vehicle-mounted thief steel protection system and the responder det, so that the operational security of the anti-theft system is guaranteed. In the known from DE 197 18 764 C1 Anti-theft system can be through appropriate transmission parameters specifically the exterior of the vehicle or the interior space of the vehicle can be queried. Should the vehicle be released are valid, the question signal is essentially in the Exterior of the motor vehicle sent. If on the other hand a drive tool user wants to start the engine, he first actuates the ignition switch, whereupon the question signal essentially in the interior of the vehicle is sent.

The invention has for its object a generic Method for operating an anti-theft system in one  Motor vehicle in terms of functionality and customization availability to different requirements ser.

The invention is further based on the object Visually improved theft protection system.

A first solution to the part of the Invention task with the features of claim 1 he aims. The fact that the interrogation signal encodes a responder contains different responders as they can for a Vehicle are normally intended to be targeted become. It is advantageous if the answerer code the question signals with which a dialogue between the driving anti-theft system and at least one answer should be triggered, on which the responder depends on from which a vehicle function was last activated because this responder is often the one with a driving tool function is activated again.

The claim 2 is for a further solution of the method relevant part of the invention task directed. Thereby, that a warning signal is triggered in the vehicle if no Ant word giver or a responder in a prohibited place is found, the security of the thief according to the invention steel protection system significantly increased.

The subclaims 3 to 9 are advantageous for further training directed towards the method of the invention.  

With the features of claim 10 is the theft protection system directed part of the invention task solved.

The invention is based on schematic drawings gene, for example, and explained in more detail.

They represent:

Fig. 1 is a block diagram of the basic structure of the anti-theft system, for the method of the invention is used,

FIG. 2 shows the block diagram of a control device contained in the anti-theft protection system according to FIG. 1.

Fig. 3 is a flowchart for explaining the operation of the anti-theft system,

Fig. 4, an information generated in the control unit of the anti-theft system for transmitting a Fragesi gnals,

Fig. 5 u. 6 flow charts for further explanation of the function and

Fig. 7 b. 10 Representation to explain the transmission ranges of individual antennas for different searches.

Referring to FIG. 1 of a motor vehicle 2 formed by coil loop antennas 4 and 6 are provided at each side. There is an antenna in each door of the four-door motor vehicle. The two antennas on one side of the vehicle are normally controlled simultaneously, but possibly with a phase shift. The antennas are connected to a control unit 8 of an anti-theft system, which in turn is connected to a motor control unit 10 , an ignition lock 12 , a central locking unit 14 and a warning device ( 15 ) with which an optical and / or acoustic warning signal can be generated. The central locking unit 14 is connected to the door locks 16 arranged on the left-hand side of the vehicle, the door locks 18 arranged on the right-hand side of the vehicle and a trunk lock 20 and possibly further locks (e.g. glove box lock).

In the vicinity of the trunk lock 20 there is a white antenna 22 , which is also connected to the control unit 8 . Instead of an antenna, two antennas can be arranged in the trunk for targeted detection of responders located there. For outdoor use, an additional antenna can be provided in the rear bumper.

A for the operation of the motor vehicle or the dialog with the anti-theft system provided answering device 24 is designed in the manner of a check card and has a transmitting and receiving unit 26 to which an antenna 28 and a transponder IC 30 are connected.

The structure of the control unit 8 is shown in FIG. 2. The control unit 8 contains a microprocessor 32 which is connected to each of the antennas 16 or 18 (only the two antennas 16 are shown) via a transmitting and / or receiving unit. The microprocessor 32 further includes a setpoint memory 36 , in which a setpoint is stored, on the basis of which a response signal received by a responder is checked for the correctness or validity of the responder. The question signal can be, for example, a random number that is encrypted in the responder according to a predetermined crypto-algorithm and is sent back in the encrypted form. This cryptographic algorithm is stored in the setpoint memory 36 so that the random number sent is also encrypted in the control device 8 and the two encrypted numbers are then checked for agreement.

The basic function of the anti-theft protection system described is explained below with reference to the flow chart in FIG. 3:

Assume that the responder 24 is in operation (stage 40 ) and that the control device 8 is also in operation (stage 42 ). Commissioning can take place, for example, by mechanically actuating an actuating element provided on the vehicle. The control unit 32 then sends with a predetermined transmission parameter set, for example, the antennas to be activated, the pulse width or transmission power and the relative phase position of the question signals supplied to the antennas, a question signal in stage 44 .

In step 46 , the responder checks whether a question signal has been received. If this is not the case, the responder remains in his request mode, in which he continuously checks whether a question signal has been received. If a question signal has been received, the responder sends a response signal in stage 48 and proceeds to stage 50 , in which the cycle in question is ended. From level 50 , the responder automatically goes back to level 40 .

After the transmission of a question signal in stage 44 , the control device switches to stage 52 , in which it is checked whether an answer signal has been received. There is a short, predetermined period of time between the transmission of the question signal in stage 44 and the possible reception of an answer signal in stage 52 . If it is determined in step 52 that no response signal has been received, the set of transmission parameters is changed in step 54 and a question signal with the changed parameter set is sent again in step 44 . This changed parameter set or a whole sequence of parameter sets with which question signals are sent is stored in the parameter memory 38 .

If a response signal is received in stage 52 , it is checked in stage 54 whether the coding of the received response signal matches the coding extracted from the setpoint memory 36 . If this is not the case, the control unit switches to stage 56 , in which the operating cycle is ended. If the authentication is OK, the respective vehicle function is activated in step 58 . In the present case, who unlocks all the locks 16 , 18 and 20 .

If the start 42 of a cycle of the theft protection system has been triggered by the ignition lock 12 , the engine control unit 10 is released in step 56 after positive authentication, so that the vehicle can be driven away.

Fig. 4 shows that the microprocessor 32 and the information generated is composed 50 for transmitting a question signal from different fields 52 in the controller 8.

A first field contains the antennas via which the respective question signal is to be sent. Another field contains the energy of the transmitted question signal in the form of its pulse width (pulse width modulation). The next field contains the mutual phase position of the query signals transmitted via various antennas. The following field contains a word encoder coding or card coding, which is stored in the transponder IC of each card, so that several cards issued for a vehicle can be addressed specifically with the question signal. Finally, the last field contains the random number that is sent with the respective question signal, provided that it is an authentication request and not just a card search request. The first three fields of the question signal thus form transmission parameters with which the type of transmission of the respective question signal can be influenced in a targeted manner. The card signal assigned to the respective question signal is stored after each stage 44 ( FIG. 3) and held in the memory as long as a question signal with changed transmission parameters is not sent. In this way, the respective card or responder is known, with which an authentication is carried out in stage 54 and a vehicle function is then actuated in stage 58 .

Which antenna is controlled with which pulse width and which phase position is stored in the processor of control unit 8 . The transmitted information consists only of the card coding or card identification (card ID) and a number, the content of which depends on whether only a card search is carried out or a challenge response is exchanged, ie authentication takes place.

In the following, examples of query strategies are explained with which a responder is searched for and then recognized. It is assumed that two responders or cards are provided for the respective vehicle and that the vehicle, as shown in Fig. 1, has two antennas on each side. The following abbreviations are used in the following tables:
ZRK: Most relevant card (card with which the vehicle function in the past was carried out)
AK: Other (not least relevant) card
NK: the card not yet found
BK: Both cards
K: the card found during the previous card search
X: any
AS: Inquiry side GEG: the GEG against the location of the inquiry
PL: phase position

Basically, the following applies to all query strategies explained below, that if a card (corresponding to responder 24 of FIG. 1) was found on a vehicle side, it is no longer searched for in the further course.

A) Query strategy for opening the vehicle

It is assumed that the vehicle is on each side is provided with a sensor, for example an infrared sensor, mechanical switch, proximity sensor, etc., used for Triggering a dialog is activated. The map search, the  Prerequisite for unlocking the vehicle is then according to the following table:

Table (a)

If a response signal is received after a search, ie after a question signal has been sent (stage 52 in FIG. 3), the search is ended and the vehicle is unlocked by the anti-theft protection system. If the card search is unsuccessful, the vehicle is not unlocked.

The search begins with the search for the last relevant Card, since in most cases with this card the vehicle will be operated again.

In order to carry out a map search more quickly, the flow diagram of FIG. 3 according to FIG. 5 can be modified in general.

The card search is carried out as described with reference to FIG. 3, the question signal, for example, only containing the card coding or identification signal, upon receipt of which the card responds with an unencrypted signal. If an unencrypted response signal is received in step 52 , a question signal is now sent in step 53 a with the number to be encrypted by the responder, but otherwise with the same transmission parameter set as the successful request in step 53 a. After receiving in step 53 b, the encrypted response signal, the authentication is performed in step 54th

B) Query strategy to release an engine start

If, for example, the ignition lock is operated, the engine can only started after successful authentication the.

Prerequisite for certain actions to be permitted, such as for example, an engine start is a unique identifier Decoration of the card inside or outside the vehicle. At the given antenna configuration answers one outside card of the vehicle only on the request signal from one side of the vehicle, whereas one inside the vehicle card located on request signals from both driving Stuff pages from answers.

The following tables illustrate a query strategy, which if the card is in an unfavorable position, a number of telegrams or queries that take a total of a few seconds can. It is advisable only after a successful map search carry out the authentication (challenge response).

An initial map search is carried out according to the following table:  

Table (b1)

If no card response is received after sending the question signal 1.16 , the card request is ended.

If in the above first search according to table (b1) a Received card response, a second will be found immediately afterwards Search for a map using the following scheme to make the map more accurate to locate:  

When the first map search, a map was in the driver's seat te found, the following second map search takes place:

Table (b2)

If a card response is received during the second card search, so there is a dialogue with the purpose of an authentic card instead of (Challenge Response) instead of one month release gate start.

After sending out the question signal according to 2.6 of the table (b2) no answer is received with the first map search continued after the map not found so far.

When the first card search was a card on the passenger page found, the following strategy is followed searches:

Table (b3)

If an answer is received during this second map search, then immediately finds a dialog with the purpose of authentication instead of. If no answer is received after the search in accordance with 2.10, is not found with the first map search for the so far continued card.

An authentication then takes place with the parameters of the card search instead. If there is no response, see above authentication with the parameters of the second card attempted tensearch.

In the two tables above of the second map search is the phase position of the question signals with only 5% pulse white any modulation because the transmission power is so low is that the radiated from the different antennas Question signals hardly overlap spatially.

The map search strategy at engine start, which was explained above with reference to the three tables, is summarized in the flow chart according to FIG. 6, which is so understandable in itself that it will not be repeated here.

C) Query strategy for locking the vehicle

Here too, the aim of the query strategy is to first carry out a map location, ie to determine whether one or more cards are outside or inside the vehicle and to initiate certain actions as a result. Specifically, this means, for example:

• - There is no card when asked to save or locking the vehicle outside and a card in the interior, the driver receives the warning that the Card is inside the vehicle. The ride stuff is then not backed up.  
• - On the other hand, there is a card in the "Save" query te in the outside area and a map in the inside, so verrie the vehicle is valid and registers the card Identification of the card in the interior te.

It is assumed below that the left side or sensors or actuators provided on the right side of the motor vehicle Actuation elements are operated for the purpose of the vehicle lock. For example, a lock can be mechanically ge can be closed or there can be an infrared sensor, a proximity tion sensor or the like can be activated.

The control unit detects the side of the vehicle from which the up The lock is carried out.

A first map search is then carried out according to the following table le:

Table (c1)

If a card response is emp in the first search above catch, finds a second map search immediately afterwards according to table (c3) above.

After an unsuccessful search, the map search is ended.

If one of the above searches succeeds and is the vehicle locked and both cards have not yet been located continue the map search according to the following table:

Table (c2)

After a map search according to the table above (c2) received a response, the message "Card in vehicle recognized "acoustically or in a display and the Query ended. Even if no card response is received, the query is ended.

A second card is found for the purpose of vehicle locking search according to the following strategy:  

Table (c3)

Will not answer after the above second map search received, the vehicle is locked and with the first Map search according to table (c1) for the one not found so far continued card.

If an answer is received after a second map search, the message "Card recognized in vehicle" is output and with the first map search according to table (c1) after the previous one card not found continued.

In the following it is assumed that the vehicle from the rear to be locked. The map search then takes place according to fol gender strategy instead of:  

Table (c4)

If an answer is received after the search, one is immediately found second map search according to table (c3) instead.

Have all searches been carried out in accordance with the table above and if there is no backup, the request is ended.

Has been saved and both cards have not yet been located, the map search continues as follows:

Table (c5)

Is an answer after a map search according to table (c5) received, the message to "Card recognized in vehicle"  issued and the request is ended. All cards were was carried out according to table (c5) and no card was er the map search is continued as follows:

Table (c6)

Have all map searches been carried out in accordance with table (c6) and if no card was recognized, the request is ended.

When searching for a map on the passenger side (1.15, 1.18 received a response from table (c6)), the message is "Card recognized in the vehicle" is output and the request is complete ends.

After a search on the driver side (1.13, 1.14, 1.16, 1.17 receive a response from table (c6)), will follow the process takes place:  

Table (c7)

Have all map searches been carried out in accordance with table (c7) and If no card is recognized, the request is ended.

Will be an answer after a map search according to table (c7) received, the message "Card recognized in the vehicle" is output enter and the request is ended.

Second card search "Secure or lock vehicle". The Map search takes place according to the following table:

Table (c8)

No response is received after sending out according to search 2.4 Save and save with the first card search continued after the map not found so far.  

If a card response is received after a second card search the message "Card recognized in vehicle" is output and with the first card search save for the previously not found card continued.

The following options are available for further processing of the card that is recognized as being in the vehicle when it is saved:

• - Possibility Number 1:
  The card is registered and blocked for further use on and in the vehicle, ie the card is informed via a separate telegram that it is blocked. As a result, the card no longer responds to a question signal. The card in the vehicle is only unlocked after successful authentication with a key or another card.
• - Option 2:
  The card in the vehicle is registered. In the subsequent "unlock" this card is no longer requested. Only after the next successful authentication with key or another card will the card remaining in the vehicle be requested again.
• - Option 3:
  The card in the vehicle when it is secured is registered. With the next request "unlock" on the vehicle, the card is requested via the antennas on both sides of the vehicle and in turn recognized as being in the interior. This card in the vehicle alone does not trigger the "unlock" action.

The telegram sequence is as follows:

Table (c9)

If a card response is received, the procedure continues as follows searched:

Table (c10)

The card may be used for searches on the opposite side (2.1, 2.2, 2.4, 2.5) can not be recognized and it must be with the repeated search can be found on the request page (2.3). Only then will the vehicle be unlocked. In the unsuccessful case  the first search for the one not found so far Card continued.

This procedure (1 find, 2 not) serves to a simple manipulation of the system by a malfunction close. According to the old procedure (once on the An Find question page, 4 times on the opposite page not find) it would be easy to turn on a sturgeon senders after the first answer the following answers to un press and thereby enable the safety release.

D) Query strategy after switching off the engine

Again, the goal of the query strategy is to start with to carry out a secure map location in order to result rend certain actions.

To localize when the engine is switched off, whether a card may be in a zero position (no reception of a Question signal is possible), a map search is carried out leads. This allows the driver to be informed that the card may not be recognized in the interior during the next backup and therefore the vehicle with a valid card inside room can be completed lying.

This map search begins immediately after the Mon is switched off tors and is then repeated continuously. The time between two polling cycles becomes logarithmic from time to time increases.

The map search only takes place as long as all doors and the Case covers are closed and as long as no combination message from the "Keyless-Go" control unit.  

The following is the search for the last relevant card explained; the same search takes place afterwards for the other card instead.

The search is based on the following strategy:

Table (d1)

The query for a card ends as soon as the card lo is calibrated (map inside the vehicle means, for example se query from both sides at full power or from one side with low power or in the trunk (in the trunk  space, two antennas are advantageously arranged, the egg locate the card there safely)).

If no card response is received after question 1.16, then the card is not in the vehicle.

If at least one card than in If the outdoor area is located, the message appears "Card not recognized" output.

E Query strategy after saving (if not through keyless go secured)

The same strategy is used here as for the engine. If at least one card inside after the completion of the query is localized, the message "Card in the vehicle er knows ". All the cards found inside are printed saved.

F Search for a map while driving

The following is the map search for the last relevant Card explained; the same process follows for the other card instead if the last relevant card was not localized.  

The map search takes place in the following order:

Table (f)

The query for a card is finished once one Response was received. Does not become after sending 1.8 Answer received, the card is not on the drive stuff. If after the completion of the query no card as on the drive is located, the message "Card not recognized "output.

G Authentication while driving

In this case, only one authentication needs to be carried out the. For this purpose, the card is not closed in the interior locate; it only has to be on the vehicle. That is why the first card search for driving authorization was not carried out.

The second map search takes place in the following order instead of:  

Table (g)

If no answer is received after question 1.16, the Repeat the above cycle for up to 5 seconds. Becomes If no card is found after 5 seconds, the message "Card not recognized ". An answer is returned after a search received, the authentication takes place. The question signal for authentication, the parameters of the previous sent out for successful card search. If there is no ant word, the request is repeated once. Is done again no answer, is continued with the second map search  drive. The cycle is repeated for up to 5 seconds, see above long no answer.

H Further query strategies

In order to inform the driver of the potential loss of his responder, an additional interior query is carried out as soon as any actuation elements of the vehicle are operated, for example:

• - Door open / closed, ignition on / off, radio on / off, change of Seat occupancy, etc.
• - window open / close,
• - trunk open / closed,
• - Sunroof open / close, and
• - Return.

If the responder does not answer, an acousti and / or visual warning.

H1 query strategy while driving

If the immobilizer for any reason, for example wise a fault from the outside, is reset, he is authentication required again. The Beibehal stands there the operational safety of the vehicle compared to the exact Location of the map in the foreground.

Fig. 7 illustrates the situation. The solid, rectangular line reflects the contour of the vehicle interior. The dashed line 62 encloses the double lobe of the field radiated by the left antenna 4 . The dash-dotted line 64 encloses the double lobe of the field radiated by a right antenna 6 . The state of maximum transmission energy is shown, since the individual position of the card or the responder 24 is irrelevant, but is crucial that the card receives a question signal. As can be seen, the interior is swept by the fields of both antennas.

H2 Parking query

When locking the vehicle, the problem arises for sure to determine whether the respondents leave the Motor vehicle at the user or within the interior is a zero, as for example by elek tromagnetic shadowing is required.

If the responder is mistakenly considered to be outside is detected sensitive, the motor vehicle can be shut off become; however, the responder is locked up and everyone can open the vehicle again.

Fig. 8 shows typical relationships. Compared to FIG. 7, the transmission power is reduced, so that the fields radiated from the antennas do not overlap outside the vehicle. The responder 24 can, however, be recognized.

To increase security against the above error can do a query before getting out of the vehicle be carried out, for example when the engine is switched off, when opening the door etc. Here is a responder inside If the vehicle is localized, a warning can be displayed.

H3 query for overreach

Exceeding ranges are caused by too high a performance, but they are out e.g. B. damping reasons is necessary elsewhere.

In FIG. 9, the lobe of the field of the antenna 6 emitted on the left has an overreach. This gives rise to the problem that the responder 24 is erroneously found when leaving the vehicle as being in the interior. Locking the vehicle off is then not possible since no key is to be locked in.

The solution to the problem is that the query takes place until the responder 24 is recognized as being safely outside.

H4 interior query with zero digits

Often zero points arise at locations that are further away from an antenna (cf., for example, FIG. 8). Increasing the performance does not offer a solution to the problem, since overreaches can then occur.

The solution to the problem is that an additional question is made with a performance that is so small that, for example, it hardly gets into the outside, but covers a considerable part of the interior. The relationships are illustrated in FIG. 10. The left lobe of the field 64 generated by the antenna 6 spreads further, for example due to the fact that it is not shielded by sheet metal, and since it is attenuated by less, than the right lobe, which has a higher attenuation. The same physical conditions apply to the field of antenna ne 4 , ie the right beam (in the vehicle interior) is more pronounced. If under the conditions of Fig. 4 of the responder he known 24, it must be located in the interior of or directly au ßerhalb the door approximately 10 cm distance.

It is understood that the above search strategies, the An order of the antennas in the vehicle and the formation of the Ant were only exemplary and varied variations possible are. One of the side antennas can move for example in an exterior rear-view mirror. The search strategies can be changed so that initially always searches for the last relevant card  and then with the same search strategy for the one or more whose cards are searched, etc.

With the invention, a significant improvement in Feh Security of anti-theft systems Motor vehicles reached; not only is it constantly checked, whether there is an authorized responder; the driver is warned when the responder is in the vehicle and this leads to a risk of theft.

Claims (10)

1. A method of operating an anti-theft system in a motor vehicle, the anti-theft system having a transmitting and receiving unit ( 34 ) arranged in the motor vehicle, which transmits a question signal via at least one of at least two antennas ( 4 , 6 ) arranged at different vehicle locations the reception of which a responder ( 24 ) sends a response signal which is received by the transmitting and receiving unit and is compared in an evaluation unit ( 32 ) with a target value, predetermined vehicle functions being activated after a positive comparison,
in which method a plurality of question signals, which are transmitted through transmission parameters stored in a control unit ( 8 ), such as the antenna used in each case, the power and the phase position of the signals fed to the antennas, until a response signal is received, wherein
the sequence of the transmission parameters with which the plurality of query signals are sent is a sequence which is dependent on the operating state of the vehicle and is a fixed sequence,
characterized in that
the question signal contains an answering device coding that is specific to different answering devices and that answering device ( 24 ) from which a vehicle function is activated is stored in the control unit ( 8 ), and the answering device coding of the questioning signals depends on the answering device from which one Vehicle function was last activated. 2. Method for operating an anti-theft system in a motor vehicle, the anti-theft system having a transmitting and receiving unit ( 34 ) arranged in the motor vehicle, which transmits a query signal via at least one of at least two antennas ( 4 , 6 ) arranged at different vehicle locations the reception of which a responder ( 24 ) sends a response signal which is received by the transmitting and receiving unit and is compared in an evaluation unit ( 32 ) with a target value, predetermined vehicle functions being activated after a positive comparison,
in which method a plurality of question signals, which are transmitted through transmission parameters stored in a control unit ( 8 ), such as the antenna used in each case, the power and the phase position of the signals fed to the antennas, until a response signal is received, wherein
the sequence of the transmission parameters with which the plurality of query signals are transmitted is a sequence which is dependent on the operating state of the vehicle and is a fixed sequence,
characterized in that
a warning signal is given in the vehicle if no responder or a responder is found at an impermissible location. 3. The method according to claim 1 or 2, characterized in that after receiving a response signal again a question signal with the same transmission parameters as the previously sent, but additional information is sent, upon receipt of which the responder emits a response signal which in the evaluation unit ( 32 ) is compared with a target value. 4. The method according to one or more of claims 1 to 3, characterized in that immediately after parking of the engine question signals with a specific sequence of over transmission parameters are sent and an error message is solved if there is no card inside the vehicle is known. 5. The method according to one or more of claims 1 to 4, characterized in that for locking the vehicle with question signals with a special sequence of transmission parameters according to the answer inside the vehicle donor is wanted. 6. The method according to claim 5, characterized in that the responder located inside the vehicle right is registered and a subsequent unlocking of the vehicle made impossible by the registered responder becomes. 7. The method according to one or more of claims 1 to 6, characterized in that when operating a vehicle control element inside the vehicle question signals with a special sequence of transmission parameters are sent and a warning is given if no responder answers. 8. The method according to one or more of claims 1 to 7, characterized in that the activation of predetermined  Vehicle functions only take place if one or more answers be located at predetermined locations. 9. The method according to one or more of claims 1 to 8, characterized in that the question signals with a for locking the vehicle locks through theft protection system-specific sequence of transmission parameters become. 10. Anti-theft system for a motor vehicle, containing tend
a transmitting and receiving unit ( 34 ) which transmits a query signal via at least two antennas ( 4 , 6 ) arranged at different vehicle locations, upon receipt of which a responder ( 24 ) which can be carried by a person sends an answer signal,
a control unit ( 8 ) provided with a microprocessor ( 32 ) with associated memory devices ( 36 , 38 ), which transmits the query signals with a predetermined sequence of transmission parameters such that the location of the responder can be determined, and
a warning device ( 15 ) which emits a warning signal if the responder is not determined at a predetermined location which is dependent on the operating state of the vehicle.