Communications: electrical – Continuously variable indicating – With meter reading
Patent
1996-08-08
1999-07-27
Zimmerman, Brian
Communications: electrical
Continuously variable indicating
With meter reading
705 28, 705400, 705 22, 359154, 177 2515, 235385, H04Q 720
Patent
active
059297700
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an electronic device for remotely displaying information on a plurality of displays, in particular a device employing the infrared (IR) transmission between the central control unit and the remote displaying units whereas the radio frequency (RF) transmission is employed in the opposite direction.
A typical application of said kind of device is in supermarkets and the like, where the variation of the prices of the exhibited products involves a long manual work for replacing the corresponding labels positioned on the shelves. Various remote displaying systems have been proposed to avoid this waste of labour, essentially consisting of a plurality of displays (typically LCD) located on the shelves as a replacement for the conventional labels and updated by means of IR, RF, ultrasonic, etc. signals emitted by a plurality of transmitters connected to a central control unit. In this way, it is sufficient to introduce the new list of prices in the central unit so that it can transmit them to the corresponding electronic "labels" in an automatic way, without any need of further human intervention. For the sake of simplicity, reference will be made hereafter to this kind of application, though it is clear that what will be said can be transferred to other similar applications.
The transmitters are usually connected by wire to the central unit, preferably using the electric cables already present for the lighting, and they make up a network of communication "nodes" each of which controls a group of labels. Furthermore, each label has an own specific "address" within a single group, so that it is possible to act separately on each single label. To this purpose, the data transmission begins with a code which identifies the label or the group of labels to which the message is directed.
For a greater system reliability it is absolutely preferable that the success of the data transmission to the labels is acknowledged by means of a reply message emitted by the latter towards their node. In order to do so, each label as well as each node must be provided with a transceiving apparatus. This allows to overcome the limits of one-way systems, such as for example those disclosed in U.S. Pat. No. 4,766,295 and in the international (PCT) patent applications WO 88/06773 and WO 90/13067. In particular, while in the first two above-cited cases the transmission takes place in IR or RF, therefore with the theoretical possibility of providing the labels with a reply transmitter, in the third case the transmission is carried out by modulating the artificial light, so that the lack of reception of a signal within a pre-established time is indicated only by the flashing of the display. It is apparent that such a solution still implies a check by the operator, and therefore can not be accepted for a system intended to reduce to the utmost the need for labour.
Examples of remote displaying devices with two-way transmission are disclosed in GB patent 2.231.994 and in the international (PCT) patent applications WO 90/14630, WO 92/08213 and WO 92/16901. The kind of transmission preferably used is the IR one, since it is immune from electromagnetic interferences, but also the RF transmission is possible as disclosed in U.S. Pat. No. 4,937,586. However, in this case the transmission from the nodes to the labels takes place by means of horizontal loop antennae which must effectively surround the whole area of the supermarket, with the cabling and positioning problems deriving therefrom. Even if other types of antennae are used for said transmission, these problems are not completely solved, particularly because the labels may be located in "shadow regions" in which the reception of the RF signal from the node may be very difficult. On the other hand, the transmission power can not be excessively increased because interferences out of the building could be generated. Moreover, the frequencies available for these transmissions are generally comprised in the band from 10 to 500 KHz, as i
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TECDIS S.p.A.
Wilson Jr. William H.
Zimmerman Brian
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