EP1069265A2 - Entry authorisation device and combined entry and user authorisation device - Google Patents

Abstract

The vehicle-side base station (14) sends a query signal to the code transmitter (1), from which test bits are sent back to the motor vehicle by bypassing an evaluation unit. The base station (14) measures the time between sending and receiving the test bits and only accepts a response signal from the code transmitter (1) if the measured time is shorter than a reference time. <IMAGE>

Description

The invention relates to a control system and method for Control at least one function of an object where Measures to prevent unauthorized use or Access to the object are met. The invention relates also an access control and driving authorization facility for a motor vehicle.

For motor vehicles are access control systems, immobilizer systems or other tax systems known (US 4,763,121), which can only be obtained if a wirelessly queried code transmitter, e.g. in the form of a smart Card or an electronic key, in their function released or controlled. Usually this is on or in the motor vehicle at least one base station with a Transmitter and receiver unit, for example for control the access control or the immobilizer device. In response to a triggering event, for example the actuation of a door handle, an ignition starter button is entered at regular or irregular intervals Interrogation code signal transmitted by a user-worn, authorized, key-serving code provider a response code signal is answered (this is also called Question-answer dialog).

The base station checks the response code signal received with regard to its justification, for example by comparison a code information contained in the response code signal with a stored reference code information. With authorization the desired function is carried out, such as unlocking the motor vehicle doors or that Release the immobilizer.

Such a system can pose security problems result, for example by unauthorized eavesdropping and manipulation wireless communication between motor vehicles and code transmitter.

To solve these problems is a control device of functions of an object, in particular the access and Driver authorization control for a motor vehicle known (DE 196 32 025 C2), in which the communication duration of the question-answer dialog measured and with a predetermined maximum duration is compared. However, the signal delays are compared to the computing times very little, so that increased Make signal runtimes not noticeable and therefore not can serve as protection against manipulation by unauthorized persons.

The invention has for its object to a control system create that through increased security against unauthorized Attempted use distinguishes without making major Interventions in the system are required.

This object is achieved with those mentioned in claim 1 Features resolved.

Furthermore, the invention is a method according to claim 8 provided an improvement over that offers unauthorized execution of the associated function.

In addition, the task is performed by an access control and driving authorization device for a motor vehicle with the features solved by claim 10.

Advantageous embodiments of the invention are in the subclaims specified.

In the invention in one of the units involved Time between sending out marked parts of a

Transmitted signal and the reception of these parts determined, i.e. it becomes the system response time to determine, so to speak the distance between the code transmitter and the object-side Base station measured. This measurement preferably takes place from energy-related or logical, system-related Reasons take place in the base station, however, depending after system design, can also be adopted by the encoder.

With an unauthorized remote inquiry result from the much longer signal paths and the internal processing times the intermediate signal amplifier significantly longer processing times and thus longer delay times between signal transmission and response signal reception than in the case of an authorized person close to the motor vehicle Code transmitter. The evaluation circuit measures in this Fall the time between signal transmission and reception at least one or more marked sections or parts of the signals and compares these time periods in the simplest case with a predetermined reference period, which entitle to receive the signal back from a Sufficient code transmitter located close to the motor vehicle due to an unauthorized remote access of the above influences are usually exceeded becomes.

According to the invention, the base station is designed such that it only executes or releases the desired function if at least the specially marked parts of the signals have been received within the specified period of time.

To internal, system-related and not exactly calculable - especially big time delays - to eradicate that through the necessary on the receiver side (for example on the code transmitter side) Processing operations with a view to receiving a Interrogation signal, the detection and evaluation of the interrogation signal, the generation / calculation of a response signal and the Sending the same are conditional, is preferably that System component generating response signal (here the code transmitter) equipped with a bypass path, at least over the bypassing a marked portion of the received signal its own evaluation circuit directly to the transmitter (transmitter amplifier and / or antenna) can be conducted and thus almost sent back to the sending component without delay becomes.

The corresponding parts are almost without delay, apart of the short group duration, reflected (transparency mode of the code provider). The delay time between sending and then receiving a signal is essentially only due to running time, so that a distance measurement to a certain extent between the base station and the code transmitter takes place. An additional analog or digital processing of the original signal would result in additional processing times with them, which are much longer than the signal propagation time in free space.

The bypass path is preferably a controllable one Provide switches so that the bypass path is only temporary direct forwarding of parts of the received Signals to the transmitter causes, but can otherwise be switched off and thus the signal communication (and the energy content) of the received signal is not impaired.

If the component equipped with the bypass path is received signal not only to the bypass path, but can also create its own evaluation circuit at the same time this the received signal on correct, for the concerned Check the component's intended code and if the code is correct (or code information) possibly an additional one Signal, for example a pulse or a pulse train, to the one sent and sent via the bypass path Append signal. This allows a further increase in Tamper-proof, e.g. versus using fake Transponders.

With multi-channel mode of operation or generally several transmission paths between the motor vehicle and the identification part (Code transmitter or transponder 1) can the above described method of operation also simultaneously with the actual code exchange take place, which makes manipulation even more difficult.

Preferably, the one that generates the question code signal Component or additional impulses, or that Question code signal, with itself from pulse to pulse or signal to Signal changing field strength, pulse duration or frequency or sequence or pulse / pause ratio. When passing them on the bypass path also gets this information the component generating the question code signal in the form of corresponding field strength, pulse length or frequency differences back, so an additional security parameter is available from the one that generates the question code signal Component by comparing the received field strength, Pulse length or frequency curve with the expected Course is evaluated. These parameters are for remote transmission hardly reproducible exactly, so deviations the received history from the actually expected history an additional indication of unauthorized vehicle use represent.

If there are several transmission channels / frequency bands an additional increase in security can be compared unauthorized access or use by switching of the transmission frequencies used. The encoder can for example from the transmitter unit during the vehicle locking process information is sent to the customer transmit frequency to be used in the subsequent opening or starting process signals, to which the encoder then adjusts itself. In a subsequent opening process, the transmitter is the code transmitter is set to the correct frequency, so that the impulses passed through the bypass path almost over the right frequency or channel without delay without settling or the like, be returned.

If at all via the remote query route then that of response code signal received remotely located can be transferred correctly, this becomes only with considerable Time delay generated. The base station may be due to this considerable time delay that of one before The code transmitter located in the signal is clearly returned by a signal supplied via unauthorized remote access, for example by specifying a time window for the response signal distinguish that when the arrival via the remote query route greatly delayed or distorted response signal supplied is already closed again, so this response signal is rejected as late.

Instead of specifying the next transmission frequency to be selected can also be another signal parameter, for example the amplitude, type of modulation or the like from the base station be ordered.

In the invention, increased signal transit times between Base station and remote code transmitters used, between one on site, i.e. close to the motor vehicle located code transmitter, and a remote and to differentiate between unauthorized queried code transmitters and only carry out or enable the vehicle function, if it is a legitimate, near the vehicle located encoder.

The invention can generally not only in the control of Access control function or immobilizer function, but also with others, only if there is a legitimate one Key functions to be performed, and also in general the authorization-relevant control of non-vehicle-related Functions of objects, e.g. access control to houses, apartments, offices, hotels, parking garages, Garages or the like are used.

The simplest way to implement the invention Case only the addition of a time slot function in the program to the base station (measurement of the time between Sending and receiving parts of signals and comparisons the recorded time with a predetermined time value). If a bypass path is added to the encoder, only the coders are designed accordingly, what likewise does not require a great deal of work or expense. The invention is thus without the need for major system interventions easy and inexpensive to implement and at different system configurations applicable without including any disadvantages during use operation (e.g. with regard to reaction times, operational safety etc.) occur.

The invention is described below with reference to the schematic Drawing based on an embodiment of the Control system described in more detail.

The invention is described below using the exemplary embodiment an access control and driving authorization device for a motor vehicle based on the single figure explained. However, the invention cannot be applied to only one Motor vehicle, but also used in other objects for which an authorization must be proven, to object-specific functions, such as access to the object Taxes.

The control system for a motor vehicle includes a portable one Code transmitter or an electronic "key" that one Transmitter 7, 8 and a receiver 2. The code encoder can be designed as a card (smart card) or in any other way and serves as an identification transmitter, which after receipt a response code signal automatically from a request signal sends back. Therefore, the code encoder is in the following as Transponder 1 called. The response code signal contains one a carrier frequency modulated for the transponder 1 characteristic binary code information.

The transponder 1 has a schematically illustrated reception circuit with the receiver 2, the radio frequency signals recorded via an antenna and possibly after demodulation to a computing unit (controller) 4, which transmits the received and processed demodulated question code signal, in particular decodes, and examines whether it is an attached to the transponder 1 directed question code signal of a vehicle-side fixed attached control device (base station 14). Is if this is the case, the computing unit 4 generates using the response code signal and / or stored information and / or a mathematical algorithm a code information that with an output amplifier / modulator 7 of a carrier frequency is modulated and via an antenna 8 as a response code signal is sent out.

The signal processing in the computing unit 4 requires one Duration that is significantly longer than the signal propagation times between base station 14 and transponder 1, which at wireless transmission of the signals. So only that pure signal propagation times measured for wireless transmission and thus a distance from the transponder 1 to the base station 14 can be determined, the transponder 1 has one Bypass path 5 as a bypass of the computing unit 4 in the form a continuous line (hereinafter referred to as bypass path 5 referred to), via which the receiver 2 directly with the Output amplifier 7 is connected.

At the input and at the output of the computing unit 4 are a controllable switch 3, 6 arranged, depending on Can be switched to the bypass path as needed. The Receiving circuit 2 is either by using switch 3 Input of the computing unit 4 or connected to the bypass path 5, whereas the switch 6 the input of the output amplifier 7 either with the bypass path 5 or with the Output of the computing unit 4 connects. The switches 3, 6 are preferably designed and constructed as a semiconductor switch controlled synchronously by the computing unit 4 such that they are either in the position shown or connected to the input and output of the computing unit 4 are.

In a modified embodiment, the receiving circuit 2 also permanently connected to the input of the computing unit 4 his. The switch 3 can then be omitted entirely or arranged in this way be either bypassing 5 with this one Connection line between the receiving circuit 2 and the Computing unit 4 connects or the bypass path 5 selectively disconnects from this connecting line. Such a design enables permanent when the bypass path is on Monitoring of the computing unit 4 even when the bypass path is switched on 5 (bypass path 5 and arithmetic unit 4 are then switched on in parallel).

The output of the computing unit 4 can also be fixed with the Input of the output amplifier 7 may be connected, the Bypass path 5 then via switch 6 either additionally connected to the input of the output amplifier 7 or from this is separated.

The control system of the schematically represented motor vehicle 9 contains a transmission unit 12, which is connected to a motor vehicle, for example attached to the outside or inside mirror Antenna 10 can send signals, and a receiving unit 12 for receiving externally supplied signals, in particular Response code signals from one of the access control or driving authorization devices assigned to the motor vehicle Transponders 1. The transmitting and receiving unit 11, 12 is with a control device 13 for controlling transmission and reception of signals, generation and evaluation of signals and for Control vehicle-specific functions, for example a central locking system or an immobilizer system, connected. The transmitting and receiving unit 11, 12 and the control unit 13 form the base station 14.

An access signal is used for access control (for example, operating the door handle or another Switch on the outside of the motor vehicle) a question code signal triggered and via the transmitter unit 11 with her Antenna 10 emitted. If there is a transponder 1 in the area is present and via his receiving group 2 the question code signal receives, it is checked in the computing unit 4, whether it's actually the question code signal for this Transponder 1 is intended. If so, generated the computing unit 4 a defined response code signal, the sent back to the receiving unit 12 via the antenna 8 becomes.

The response code signal contains encrypted code information, which is checked in the base station 14 for authorization becomes. If the response code signal is justified, it will be shown below described runtime analysis and if necessary then access by unlocking door locks enables.

The same process takes place to release the immobilizer and start the internal combustion engine. As a trigger of the An ignition start switch is used for the question-answer dialog. Consequently the motor vehicle can be used, i.e. the driving operation is released. The same operating procedure also applies the control of another vehicle-specific function, for example user-specific settings of seats or mirrors, or release of use from mobile phone or internet in the motor vehicle too.

So that the functions can only be controlled if the authorized transponder 1 also in the vicinity of the motor vehicle or is arranged in the motor vehicle, is additional still considered the signal runtime. The Switches 3 and 6 temporarily switched so that one or several marked or marked parts or sections (hereinafter referred to as check bits) of the question code signal directly to the transmitter 7, 8, while at least the remaining parts of the question code signal of the computing unit 4 are supplied.

The check bits are one or more bits of a binary (encoded) Information contained in the question code signal as one Carrier frequency is present modulated or the one separately binary information transmitted by the question code signal is. The check bits can be at the beginning or at the end of the question code signal be transmitted. You can also within the Question code signal on one or more predetermined Positions are transferred. You can also use it multiple times of the question code signal appear, and this with a predefined number of bits (= length of the test bits).

Codierung", die nur Basisstation 14 und Transponder 1 kennen. Diese Codierung kann sich nach einem festgelegten Zufallsprinzip ständig ändern. Die Basisstation misst die Laufzeiten der Prüfbits, und zwar vom Aussenden bis zum Empfangen der Prüfbits.This creates an additional one

Coding ", which only base station 14 and transponder 1 know. This coding can change continuously according to a fixed random principle. The base station measures the transit times of the test bits, namely from transmission to receipt of the test bits.

The base station 14 is designed so that the time the transmission of a signal via the transmission unit 11 and the Receipt of a response signal detected via the receiving unit 12 (especially the check bits relevant for the runtime). So there is a real-time measurement in the base station 14 instead of starting with sending test bits by base station 14 and the end by receiving the corresponding test bits given by the base station 14 is.

The runtime of the check bits, i.e. from transmission by the transmission unit 11 until reception by the receiving unit 12 is measured and with a maximum permissible reference term compared. Only if the runtime of the check bits is within the reference term and the code information entitles functions are controlled in the motor vehicle.

The reference running time is determined during an initialization phase (for example at the end of the assembly line during the manufacture of the motor vehicle) in such a way that the running time of a signal is measured, which is sent to a transponder 1 that is at a fixed, short distance from the motor vehicle and is transmitted directly from it A tolerance value (for example 50%) is then added to the measured transit time value (possibly averaged over several measurements). The reference transit time thus obtained is much smaller than a transit time taking into account the processing time in the computing unit of the transponder 1.

The maximum permissible reference term is in one configuration without bypass path 5 dimensioned so that a response code signal from a place far from the motor vehicle Transponder 1 is recognized as not permitted. So if that Response code signal via an unauthorized remote access to the remotely located transponder 1 is requested, result themselves much longer terms, so the sum of all Time delays are significantly greater than with one nearby or transponder 1 located in the motor vehicle.

The transponder 1 should be used in a motor vehicle a maximum of only a few meters from the motor vehicle his. Only then should access be possible.

To reduce the time interval between sending a Signal by the transmitter unit 11 and the return of a Response signal from the transponder 1 by the receiving unit 12 switches 3, 6 and bypass path 5 are provided, so that the time delay caused by the computing unit 4 (for the billing of the received code and the subsequent one Generation of the code information for the response code signal) can be suppressed. This is a direct one in transponder 1 Transfer of the test bits of the Signals via the bypass path 5 to the output amplifier 7 and to antenna 8 possible. These check bits are through the antenna 8 immediately sent out again, even if the response code signal is only fully returned later.

The direct electrical connection between the receiving circuit (s) 2 (the number of receiving channels depends, for example on the number of channels or frequency bands ab, which can be covered by the identity provider) and the Output stage 7, 8 is from the computing unit 4 by appropriate Position of switches 3, 6 controlled.

Initially, switches 3 and 6 are in the idle state a switching state in which the input of the computing unit 4 is directly connected to the receiving circuit 2 and the output the computing unit 4 to the input of the output amplifier 7 connected. If now the base station 14 via the transmitter unit 11 sends out a question code signal to the Transponder 1 is directed, so the beginning of the question code signal recognized by the computing unit 4. The transponder 1, i.e. the computing unit 4 and its switches controlled by it 3, 6 are synchronized so they arrive on time of the check bits in the transparency mode and after switch back the check bits.

Since both the base station 14 and the computing unit 4 the Knowing the coding "of the test bits (for example, each stored in a memory such as an E ² PROM or communicated as coded information to the receiving unit), the computing unit can then - starting with the first bit or start bit of the received binary information - switch 3 and 6 synchronously switch at the times specified by position / position and / or length and / or number of test bits so that the test bits are routed via the bypass path and immediately sent back in. The transponder 1 is then (during the bypass) in a so-called transparency mode. At least the other parts of the question code signal are fed to the computing unit 4 in order to form the answer code signal with the help of the question code signal.

The evasion process advantageously takes place within a running, possibly encrypted data stream, namely within the question code signal and the answer code signal from. Then it is difficult for unauthorized persons recognize where the check bits are, how big they are and how many there are.

It is advantageous if immediately before and immediately after the check bits contain no information in the question code signal is so that switches 3 and 6 have time switch and no information during switching get lost. Such a pause in impulses does not occur anyway on, since a binary, encrypted information is constantly Pulse pauses and pulses with different lengths having. An unauthorized person can therefore determine the location of the check bits do not read out from the question code signal or the answer code signal.

A start signal can also be sent through first that the computing unit 4 is synchronized. The start signal can have one or more short pings that are considered as check bits and sent back directly become. Then the actual question code signal sent and then the response code signal are generated. The pings can also be sent out after the question code signal However, there may be interference with the response code signal come as the pings instantaneous and the response code signal due to the processing time in the computing unit are sent out with a delay by transponder 1.

The base station 14 determines the time period between transmission the respective check bits and their return and compares this time period with the reference time period.

The computing unit 4 switches the switches 3 and 6 in such a way that the check bits are routed through the bypass path. The Switches 3 and 6 can also be designed so that the Check bits both via the bypass path and in parallel are fed to the computing unit 4.

With an authorized response code signal and compliance with the maximum permissible time interval when returning the or the The base station 14 triggers test bits to perform the desired function off, for example unlocking the motor vehicle doors or starting the engine.

Alternatively, the control system can also be designed such that the computing unit 4 after receiving the first question code signal first sends the response code signal back to base station 14 and only then switches 3 and 6 into the position shown switches, after which the base station 14 or the Check bits for determining the response time until receipt the response impulses generated. As another alternative, you can the computing unit 4 fixed between the receiving circuit 2 and the output amplifier 7, and it is parallel to Computing unit 4 selectively bypass path 5 at least one controlled by the computing unit 4 Switch can be switched on or off. This can be the bypass path 5 be switched on in the idle state so that the pulses or code signals transmitted by the base station 14 can be processed and processed simultaneously by the computing unit 4 the bypass path 5 can be returned to the base station 14.

The computing unit 4 can then be designed so that there is a additional pulse train or a single pulse generated and this to the through the bypass path 5 Check bits for additional identification confirmation attached.

The base station 14 can also be designed such that it the transmitted test bits in their field strength, pulse duration or frequency varies according to a predetermined scheme. This "Modulation" remains in transponder 1 during transmission receive the bypass path 5 so that the over the exit circuit 7, 8 returned pulses also this modulation contain. In this case, the base station 14 additionally measures the varied parameter, i.e. the field strength, pulse length and / or frequency change and only accepts pulse trains, that change in the expected way.

Correction factors dependent on field strength can also be transferred to runtime differences due to large dynamic differences to be able to compensate.

Alternatively or additionally, you can use the base station 14 and the transponder 1 several transmission paths, in particular several frequency bands or at least several channels be provided within a frequency band. The above The specified security measures can then be carried out simultaneously with the actual Code exchanges take place, which is an unauthorized manipulation even more difficult. So the question code signal with the check bits for example at 125 kHz and the response code signal and the test bits are returned at 433 MHz.

So that the transponder 1 has several frequency bands on the transmission side or sweep at least several channels within a band can, it is designed for example in PLL technology and can optionally have a plurality of for different Output circuits designed for frequencies or channels 7, 8 have. The transmitter and receiver unit also open the motor vehicle side are then also for several frequency bands or multiple channels within a band. This can be used to advantage in that that the base station 14 the transmission frequency used in each case or changes the channel used and the transponder 1 the transmission frequency or channel to be used in advance, for example, by means of a corresponding code signal communicates. This allows maintaining a proper one Communication between the base station 14 and the Transponder 1.

The base station 14 can make the transmission frequency dependent, for example, on the respective input code or another code segment, for example a secret key, so that a constant frequency change, for example dependent on the bit status or the checksum or the like, results. Since only the base station 14 knows the codes and thus the new frequency to be used in each case, only the connected receiver can also carry out the correct frequency jump. This makes unauthorized eavesdropping difficult. The previous one Communicate "can of course also apply to the position / length / number of check bits.

In one embodiment, base station 14 shares this Transponder 1 during a locking process of the motor vehicle in the form of a code signal with which frequency at the next contact, namely with the access control authorization query the next time you try to open the door, will be used. The transponder 1 can then on set this new frequency and at the next communication send on this frequency. For unauthorized use Remote query means remains the one to be used next Frequency unknown.

Alternatively, it is also possible for the transponder 1 to be active the frequency to be used and the frequency change defined and the base station 14 over it in the form of code signals informed.

The precautionary measures given may vary depending on System design only for itself or in any Combination may be provided.

When the carrier frequencies of the signals are substantially the same then the route that is routed via the bypass path 5, immediately returned signal with that from the computing unit 4 overlay the upcoming transmission signal so that interference effects, Zero crossing fluctuations and thus phase changes, as well Mixing frequencies occur at the receiving unit 12 that of the base station 14 can be detected (e.g. via a Phase comparison or an interference pattern evaluation). This enables an even more precise measurement of the delay times / running times that have occurred up to a distance measurement.

The question code signal and the answer code signal are code signals, which each have a binary information that one Carrier signal are modulated. The binary information points many bit positions. By encrypting the code signal changes with every new encryption process. The code information can precede or succeed several bits that may be required for secure data transmission become. The code information comes with an expected and target code information generated or stored at the receiving end compared.

Under the term Question code signal "for the invention is to be understood as a signal that contains encoded information and the check bits (even if the check bits are sent sooner or later) and serves as a request to send the answer code signal. Also under the term Answer code signal "to understand a signal that has both code information and the check bits, even if these parts arrive at the respective receiver at different times.

For a specific embodiment it is assumed that the code information for the question code signal has 64 bits and by a signal with a frequency of 4 kbit / s (1 bit = 250 µs length or bit width) is displayed. This code information becomes a carrier signal with the carrier frequency of 125 kHz modulated. Within the code information for example, beginning with the 20th bit position - three check bits (corresponds to a duration of about 750 µs) marked. The average throughput time (duration) of the check bits starting with the sending of the question code signal and ending with receiving the check bits immediately in transparency mode were sent back by transponder 1, amounts in the case of a transponder 1 arranged close to the motor vehicle about 20 µs (due to the running time at 125 KHz or 433 MHz). The value 25 µs could serve as a reference runtime if 5 µs added as a safety tolerance. So if a term is measured for the test bits of less than 25 µs, so the authorized code information of the transponder 1 required to have the desired functions in the motor vehicle to execute.

As additional security, multiple check bits could also be used be arranged in the question code signal, for example a Check bit starting at the 20th bit position with the number of 3 Bits and starting at the 43rd bit position with the number of 2 Bits. If the runtimes of the check bits are shorter than the reference term and also the two lengths of 3 bits and 2 with a corresponding time interval to each other and would be correctly captured at the right time, so would the response code signal recognized as justified with regard to its check bits.

The computing unit 4 is advantageously a microprocessor trained with associated memories. The control unit is also 13 as a microprocessor with associated memories educated. The transit time measurement can be done by a separate Unit. Likewise, the runtime measurement be made by the microprocessor.

Claims (10)

Control system for controlling at least one function of an object with a base station (14) arranged on the object side with a transmitting and receiving unit (11, 12), and with a portable code transmitter (1) which is in response to an interrogation signal sent by the transmitting unit (11) sends a response signal, the code information contained therein is checked in the base station (14) for its authorization, the base station (14) executing or releasing an object-specific function when the response signal is authorized, the base station (14) and / or the code transmitter (1) Determines the time between the transmission of at least part of the query signal and the reception of a part of the response signal obtained in response thereto, compares it with a predetermined reference time period and the base station (14) only releases or executes the function, even if the code information of the response signal is correct, if the measured signal Period is shorter than the reference period, characterized in that the code transmitter (1) or the base station (14) has an evaluation circuit (4) for evaluating the code information and a bypass path (5) via which parts of the received signal are bypassed by the evaluation circuit (4) to a transmission antenna (8 , 10) can be created. Control system according to claim 1, characterized in that in the bypass path (5) at least one switch (3, 6) for selective Activation and separation of the bypass path (5) is arranged. Control system according to claim 1 or 2, characterized in that the received interrogation signal at least temporarily in parallel to the evaluation circuit (4) and the bypass path (5) is created. Control system according to one of the preceding claims, characterized characterized in that the evaluation circuit (4) designed is that they can be accessed via the bypass path (5) Transmitting antenna (8, 10) passed signal an additional signal appends. Control system according to one of the preceding claims, characterized characterized in that the base station (14) and / or the Code transmitter (1) send out one or more impulses, which the bypass path (5) and the transmitting antenna (8, 10) for transmission Unit to be returned. Control system according to one of the preceding claims, characterized characterized in that the base station (14) and / or the Code transmitter (1) sends out a pulse or code sequence that additionally in the amplitude, the pulse duration and / or the frequency is modulated, and that the evaluation circuit (4) additionally to measure the time between sending and receiving the Pulse or code sequence of their amplitude, pulse duration and / or Frequency checked. Control system according to one of the preceding claims, characterized characterized in that the base station (14) and the code transmitter (1) for multiple frequency bands or multiple channels are designed within a frequency band and each used transmission frequency is changed. Method for controlling at least one function of an object, in which an authorization check is carried out between a base station (14) on the object side and a portable code transmitter (1) by transmitting an interrogation signal, retransmitting a response signal and checking code information contained in the response signal for authorization, and the Function is released or executed only with authorization, and in which the time period between the transmission of at least a part of the query signal and the reception of a part of the response signal obtained in response thereto is measured, compared with a predetermined reference time period and the desired function only if the code information is correct is released or executed when the measured time period lies within the predetermined reference time period, characterized in that the transmitted signal by one or more, possibly in their amplitude, impu The duration and / or frequency of the changed pulse is formed, which in the component receiving this signal is routed to the transmission circuit of this component without evaluation processing via a bypass path and sent back to the other component. A method according to claim 8, characterized in that the number of parts of the interrogation signal that go through the bypass path be passed, the length of each part or the position of the parts within the response signal is evaluated as well as compared with expected values. Access control and authorization device for a motor vehicle with a base station (14) arranged on the vehicle with a transmitting and receiving unit (11, 12) which transmits an interrogation signal and then waits for a response signal, a portable code transmitter (1) which has a receiver (2) and a transmitter (7, 8), by means of which a response code signal is emitted after receipt of a request signal,
characterized, that the code transmitter (1) has a switchover device (3, 6) that directs predetermined parts of the received query signal directly from the receiver (2) to the transmitter (7, 8) via a bypass path (5) and the rest of the request signal via a computing unit ( 4) to the transmitter (7, 8), that the transmitting and receiving unit (11, 12) has an evaluation unit (13) and a time measuring device (13), which evaluate the response signal on the one hand with respect to authorization and on the other hand with regard to signal transit time, and allow access to the motor vehicle and / or an immobilizer is released .

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