Communications: electrical – Land vehicle alarms or indicators – Of burglary or unauthorized use
Reexamination Certificate
2000-03-27
2001-11-13
Pope, Daryl (Department: 2632)
Communications: electrical
Land vehicle alarms or indicators
Of burglary or unauthorized use
C340S870030, C340S870030, C340S010200
Reexamination Certificate
active
06317035
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to an apparatus for enabling and/or activating/deactivating a security device, in particular an access device for a motor vehicle, in which, after receiving a stimulation sequence which is transmitted by a transmitter of a transmission device, coded information (enable signal) is transmitted by a portable transmission unit (radio key) and is received by a receiver in the transmission device, with a controller comparing the received enable signal with predetermined coded information and, if they match, emitting an actuation signal to the security device.
In order to improve the convenience of use of access security devices, for example the central locking system of motor vehicles, electronic radio keys have recently come into use, which transmit an electromagnetic enable signal to the security device on pressing a button or completely automatically, and the said device then enables access. In these devices, the radio keys replace the conventional mechanical keys.
An apparatus for operating a door locking and/or alarm system is known from WO 92/18732. In this system, the user carries a radio key in which an enable code is stored in order to activate and deactivate the said security devices. The motor vehicle contains a transmission apparatus, which receives an enable signal transmitted by the radio key, and compares it with a stored coding. If the codes match, an actuation signal is transmitted to the security device (central locking system, alarm system).
The enable signal is transmitted only when the person carrying the radio key is at a predetermined distance from the motor vehicle, which is within the range of the transmitter in the transmission apparatus. The radio key is activated by a stimulation sequence from the security device, without any manual action by the user.
Such a system is generally supplied with a number of matching radio keys. Normally, these keys may be distributed between a number of vehicle users. It is thus possible, once the stimulation sequence has been transmitted, for the security device to receive a response signal from a number of radio keys within range of the security device. This can lead to a collision resulting from all the keys transmitting signals without any coordination, so that the controller of the security device is unable to correctly identify an enable signal and to decide which of the signals is intended to be used as an enable signal.
Systems are known which, if there is any such suspicion, address all the radio keys in a system globally and, if the response is not clear, address individual radio keys selectively, one after the other. This has the disadvantage that, as the number of radio keys which a security device may have and which are located within range of the security device increases, the time required for the data interchange increases, so that the vehicle user is not allowed access to the vehicle until a noticeable time period has passed.
Since, as a rule, the radio key signals are quite weak and are transmitted poorly over a lengthy distance, interference can occur if the transmission path is poor. If interference occurs, the security device must once again select a radio key, and request it to transmit an enable signal. This once again results in a noticeable delay.
SUMMARY OF THE INVENTION
The object of the present invention is to specify an apparatus of the type mentioned initially, in which one radio key from a set of existing radio keys may be used to transmit the enable signal without any significant time delay. Furthermore, a method for its operation is to be specified.
According to the invention, the object is achieved in that the stimulation sequence (challenge signal) comprises a first message part with an identity of the security device, and a second message part, in which case the first message part excites those radio keys which are located in a predetermined area of a transmitter of the transmission device and match the security device to each emit a response signal with a mutual offset at different times during the transmission of the second message part, and in that the controller uses the response signals to select a suitable radio key from the set and to emit a selection signal which causes the selected radio key to emit the enable signal.
One advantage of the invention is that the presence of the radio keys within range of the security device is acknowledged even while the stimulation sequence is being transmitted. The controller can thus use the response signals to select a suitable one of the radio keys without any time delay, and can transmit the selection signal for the desired radio key, as part of the stimulation sequence, immediately following the rest of the stimulation sequence. No time delays occur as a result of the evaluation of the response signals from the various radio keys. The time required for the data interchange does not, in particular, exceed the time period required for transmission of the stimulation sequence.
A first refinement of the invention provides for the capability to transmit the response signals from the radio keys in synchronism with the second message part, in order to allow the controller to distinguish the response signals.
The response signals may be distinguished more easily if the response signals from each radio key are synchronized to in each case one other flank of the second message part.
The reception area of the transmission device is generally limited to a few meters or tenths of a meter. The signal transmission times between the radio keys and the transmission device are thus negligible. The transmission of the respective flanks of the second message part occurs approximately at the same time as the reception of the response signals, and the controller can determine which radio key has responded.
As an alternative to this, it is possible for the individual radio keys to transmit their response signals at different time intervals after receiving the first message part of the stimulation sequence.
The controller can thus use the fixed-defined times for the acknowledgement to determine which radio keys are within range. Once the controller has selected one of the radio keys, it expressly requests this key to return the enable signal, in the knowledge of which radio keys are present.
In order to allow signals to be transmitted and received in parallel, it has been found to be advantageous for the stimulation sequence to be transmitted in a frequency band that is different to that of the response signals.
It is also advantageous for the stimulation sequence and the selection signal to be transmitted as longwave signals, and for the response signals and the enable signal to be transmitted as shortwave signals. In this way, the signals do not interfere with one another, and the portable radio keys may be designed to be very compact, since they do not require a longwave transmitter.
In order to define the second message part, a next refinement of the invention provides for the transmission device to have a first computation unit, and for each radio key to have one second computation unit, for algorithms to define the second message part to be stored in the computation units, and for the second message part to be redefined independently, using the algorithms in the computation units, after each transmission has been made. This improves the security of the apparatus according to the invention against unauthorized operation.
Further advantageous functions can be achieved if each response signal contains further information that is characteristic of the respective radio key. For example, if the invention is used in hotels, this allows only the hotel personnel radio keys to be enabled when the room occupier is not present. It is also possible to inhibit individual matching radio keys. For example, radio keys which have been lost can thus easily be made unusable, and this is an advantage over the use of mechanical keys.
In a method for enabling and/or activating/deactivating a security device, in particular
Berberich Reinhold
Bürger Thorsten
Hassler Gregor
Sievers Christopher
Farber Martin A.
Mannesmann VDO AG
Pope Daryl
LandOfFree
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