Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1996-08-27
1998-11-17
Hofsass, Jeffery
Communications: electrical
Condition responsive indicating system
Specific condition
340568, 340541, 340539, G08B 1314
Patent
active
058382348
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to method and device for sensing, identifying and protecting goods, particularly from theft.
It also applies to protection against unauthorised use of objects in a large controlled space such as a superstore or the like, an office building or even an industrial facility.
2. Description of the Prior Art
To perform such protection, there has already been proposed, in patent application FR 2 700 872 filed in the name of the applicant hereof, a method consisting in fitting the objects to be controlled with a tag comprising a transmitter of limited range. This transmitter is controlled by a sensing device in order to be capable of switching from a stand-by condition to an ON condition in which it transmits an alarm signal containing an identification message after the sensor has sensed a parameter representative of an unauthorised use of the object. This method further uses, in appropriate places in the controlled area, local units comprising respective receivers capable of transmitting, to a central processing unit and after reception of an alarm signal transmitted by an object, information pertaining to this object and its position at the time of the reception.
In the event of the object to be controlled having to remain stationary in a given place in the space to be controlled, the sensor can consist e.g. of an accelerometric sensor or an inclinometer capable of sensing a displacement or change of angle of the object.
It so happens that this solution has the drawback of only being usable for a very limited number of applications.
Moreover, market requirements demand the manufacture of miniature tags of the smallest possible space requirements, in order to make it possible to attach them to small objects, and yet that they be as autonomous or self-contained as possible.
However, the power consumption of tags is mainly due to the consumption of the radioelectric transmitter contained in the tag. Given the fact that the transmitter must have a minimum range that cannot be reduced, in order to increase the autonomy of the tag while limiting its power consumption it is necessary to ensure that the transmission time of the alarm signal is reduced to the strict minimum.
To this end, the utilisation of a delay circuit limiting the period of transmission from the moment said parameter is sensed, is not satisfactory. When a device is authorised to change place within a room, but without leaving the latter (the exit from the room being fitted with a receiver), the tag's power source can discharge itself subsequent to a multiplicity of authorised displacements without the receiver having been called into play.
OBJECT OF THE INVENTION
The main object of this invention is to remedy these drawbacks.
SUMMARY OF THE INVENTION
Accordingly, there is provided a method of the above-mentioned type according to which the transmitter circuit is only powered on the twofold condition that the tag has been cleared subsequent to a sensing of the above-mentioned parameter and that it receives an activating signal transmitted permanently by a transmitter device associated preferably with the receiver circuit.
Advantageously, the range of the receiver will be longer than that of the transmitter of the activating signal in order to be able to sense, over a large area, the alarm signal transmitted by the tags activated by other means or by tags responding directly to the sensing of the controlled parameter, and, in a narrower area, e.g. a transit area, the alarm signals coming from tags cleared to transmit and which have been activated by the activating signal.
Of course, the device implementing the method previously described will have to use, on the one hand, at least one local unit, possibly coupled to a central processing unit, and comprising a transmitter circuit capable of transmitting an activating signal as well as a receiver circuit capable of receiving. an alarm signal transmitted by a tag, and, on the other hand, at least one tag associated with a
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Hofsass Jeffery
Lee Benjamin C.
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