Automatic control device for an anti-theft system
This invention relates to an automatic control device for an anti-theft system.
Known anti-theft systems installed in a motor vehicle, a dwelling or any other place to be subjected to surveillance require their central electronic control unit to be activated by a manual command using a key or a remote control device when the user departs, and to be deactivated by a reverse operation when surveillance is no longer required. The activation and deactivation of the system therefore require a voluntary action by the user, which may sometimes not be forthcoming due either to hurry or to forgetfulness, and sometimes be difficult and uncomfortable to achieve if the user is carrying bags, packages or umbrellas in his hands, or if he does not have the key or remote control device to hand. This problem is solved according to the invention by an automatic control device for an anti-theft system provided with a central control unit, as described in claim 1.
A preferred embodiment of the present invention is described hereinafter with reference to the accompanying drawings, in whi h:
Figure 1 is a schematic perspective view of the device according to the invention, used for activating an anti-theft system for motor vehicles. Figure 2 shows one example of the block diagram of the device, and Figure 3 shows another example thereof.
As can be seen from the figures, the device according to the invention is used for activating an anti-theft system installed on a motor vehicle 1, in which a conventional central control unit 2 is installed on the vehicle to act on the door locks, on the motor feed and on a plurality of sensors for detecting any break-in attempts. The device of the invention also comprises an exciter circuit 3 associated with the control unit 2 and comprising a transmitter 4 and a receiver 5. The transmitter 4 is able to generate periodic scanning pulses and to radiate them at a predetermined carrier frequency Fl preferably of between 10 and 100 KHz. In practice each pulse consists of a train of coded pulses which provide "personalization" of the device.
The range of these scanning signals is commensurate with the use of the device and in the case of an anti-theft system for a motor vehicle is of the order of 0.5-2 m. The receiver 5 of the exciter 3 is tuned to a frequency F2 different from Fl and preferably between 10 KHz and 100 MHz. The transmitter 4, the control unit 2 and the receiver 5 are preferably powered by the same vehicle battery. The device of the invention also comprises a portable receiver-transmitter of minimum dimension, for example similar to a cigarette lighter, and of very low power consumption such that a normal battery lasts a long time, for example more than one year.
The receiver-transmitter 6 comprises a receiving section 7 tuned to the frequency Fl and able to receive the coded scanning signals fed by the transmitter 4, and a transmitting section 8 which on receiving a scanning signal generates a coded response signal at the frequency F2 and with a range of 0.5-2 m.
The various circuits of the exciter 3 and portable receiver-transmitter 6 are connected together to mutually interact, as apparent from the following description of operation.
The transmitter 4 of the exciter 3 emits periodically and automatically, for example every 10 seconds, a coded scanning signal at the frequency Fl. If the receiver- transmitter 6, carried in the pocket of the driver, lies within the radius of action of said transmitter 4, signifying that the driver is either on board the vehicle or in its immediate vicinity, this scanning signal is detected by the receiving section 7 of the receiver-transmitter 6, which then causes the transmitting section 8 to emit a coded response signal at the frequency F2. This response signal is received by the receiver 5 of the exciter 3, which acts on the central control unit 2 in the sense of keeping the anti-theft system deactivated.
If however the coded scanning signal is not received by the receiving section 7 of the receiver-transmitter 6, signifying that the driver is at a distance from the vehicle, no response signal is emitted by its transmitting section 8 and no signal is therefore detected by the receiver 5. Under these circumstances the exciter circuit 3, after a predetermined time from the emission of the scanning signal and preferably greater than the time between successive pulses, acts on the control unit 2 in the sense of causing it to activate, or maintain activated, the anti-theft system and, if required, the optical-acoustic detection systems, in a predeterminted manner.
In this respect, the driver has only to distance himself slightly from the vehicle for the anti-theft system to be automatically activated, to then be automatically deactivated as soon as the approaches he vehicle, and remain deactivated for all the time he remains on board.
In a different embodiment, not shown on the drawings. instead of using two different frequencies Fl and F2, a single frequency Fl can be used and the receiver 5 be disenabled during transmission of the scanning signals by the transmitter 4 to prevent said receiver 5 being able to detect pulses from said transmitter 5 instead of from the transmitting section 8 of the portable receiver-transmitter 6.
In both the described embodiments the receiver- transmitter 6 is powered by its own battery, which has a very long life due to the very small energy consumption, which mostly derives from the response pulses. It is however possible to use unpowered apparatuses, so making their life practically unlimited.
An apparatus of this type is shown schematically in Figure 3. In it the mobile receiver-transmitter 6 is of the passive type and comprises a resonant LC circuit tuned to the frequency Fl. It is apparent that when this circuit is within the field generated by the scanning pulses it represents for the transmitter 4 a load which appreciably lowers the level of the emitted signal.
In the exciter 3 a circuit is provided able to sense this signal reduction and, each time this happens, to act in the same manner as the receiver 5 would have acted on receiving a response signal from the receiver-transmitter 6.
The device according to the invention has been described in connection with its use as anti-theft system installed on a motor vehicle. In this use it is preferable to take particular measures suitable to prevent that the activation of the anti-theft system can cause circumstances of safety both for third parties and for the same ill-intentioned person who in some way has entered inside the vehicle. More particularly it is foreseen that, in the case an ill- intentioned person has forced the lock of the vehicle, started engine and run away with the same vehicle, at the activation of the anti-theft system the following events will occur in automatic sequence:
- the lighting of an alarm lamp at the inside of the vehicle to signal to the driver the occurred activation of the anti-theft system,
- the visualization of a signal warning the driver that the vehicle will stop within a prefixed time,
- the activation of all the optical and acoustic signalizations with which the vehicle is provided,
- the interruption of the feeding of the engige both with respect to the fuel and to the electric power.
The device of the invention, the described embodiments of which relate to the control of the central control unit of an anti-theft system installed on a motor vehicle, can also be used in other sectors, for example in a dwelling, and in general in any place which it is desired to protect automatically each time the responsible person is absent. It can also be used for other purposes not directly related to an anti-theft system, such as to automate the opening of doors in general or for the most varied industrial applications.