GB2231994A - Information display system - Google Patents

Abstract

An information display system of the kind in which information is displayed on a plurality of individual display units, each of which can receive display pattern control signals addressed thereto from one or more transmitter units remote therefrom, the system being characterised in that the control signals are optical signals. Preferably the optical signals are infrared signals. Preferably the system is applied to a supermarket and comprises a control module (1 ) positioned so as to be able to transmit and receive infra-red signals, to/ from individual LCD price display units (3) mounted on the shelving so as to alter the displayed price. The control module (1) may be controlled from a suitable control interface to which it is connected by the existing mains wiring of the supermarket. The display units (3) may include a transmitter so as to be able to transmit confirmatory infra-red signals to control module (1). The display units may include a solar cell as a source of energy. <IMAGE>

Description

INFORMATION DISPLAY SYSTEM Background to the Invention The invention relates to information display systems, and more particularly to price display systems for, for example, a supermarket or other retail outlet.

One conventional way of displaying the price of a product on sale in, for example, a supermarket, is to mount a display card on the edge of the shelf holding that product. The display card usually includes information on the nature of the product and one or more price bearing labels removably mounted on the display card.

With this arrangement, the price to be displayed can be determined by appropriately selecting which labels are to be mounted on the display card. The drawback with such a system is that the updating of a display price is a manual operation which involves an operative travelling to the display card in question. In many cases, particularly in larger stores, there are often a large number of display cards distributed over a wide area, thus making the process of updating the displayed prices labour intensive, time consuming and prone to human error.

In an attempt to overcome these problems, it is known to replace the conventional display cards with LCD display units.

Each LCD display unit includes a number of conducting brushes which are, in use, in electrical contact with a corresponding number of conducting tracks situated on the shelf edge on which the display unit is mounted. The tracks are linked to a control unit via a network of cables, and provide the power needed to operate the display units. When the price displayed on a particularly display unit is to be altered, a control signal addressed to that unit is transmitted to it along the tracks, and is picked up by the conducting brushes.

The system thus enables the displayed prices to be remotely updated.

However, the installation of the tracks and connecting cables can be a costly and disruptive process. Additionally, over the course of time, dirt and grease may accumulate on the tracks, impairing the contact between the brushes of the display unit and its respective tracks.

In one broad aspect, according to the invention, there is provided an information display system of the kind in which information is displayed on a plurality of individual display units, each of which can receive display pattern control signals addressed thereto from one or more transmitter units remote therefrom, the system being characterised in that the control signals are optical signals.

Preferably the optical signals are infra-red signals.

As well as having means receiving the optical control signals, each display unit may, with advantage, also include a transmitter for optical signals. This feature enables each display unit to transmit a signal confirming that, for example, a control signal to that display unit has been received, or that the instructions contained in the control signal have been executed.

The invention also provides a display unit for use in the price display system, which display unit includes a solar cell so connected to the rest of the display unit that the or part of the energy needed to operate the display unit is provided by the output of the solar cell.

The solar cell is of the kind which converts light energy into electrical energy, and is capable of operating using artificial light as well as sunlight. These display units can thus obtain power from the store lighting.

Preferably, the system includes a plurality of transmitter units for the control signals. Each transmitter unit may be connected to the mains electrical supply for the store, and may itself be controlled by instructing signals sent via a mains born communication system, i.e. a system in which signals are transmitted to the transmitter unit through the mains wiring.

Where there are a plurality of transmitter units, the system may, with advantage, include the feature that the control signal addressed to a particular display unit is transmitted only by the transmitting unit (or transmitting units) in the range of the display unit.

In this case, in another aspect, the invention provides a method of ascertaining which transmitter units are in the range of a given display unit, the method comprising the steps of: (a) causing a transmitter unit to transmit a test signal addressed to the display unit; (b) providing that the display unit transmits a confir mation signal if it receives the test signal, but not if no test signal is received; (c) monitoring the output of the display unit transmitter; and (d) repeating steps (a) to (c) for each transmitter unit in turn.

Since the display units are powered by solar cells, and are controlled by optical control signals, the system avoids the need to have cables and tracks connecting the display units to a power source and a control signal generator. Moreover, where the transmitter units are controlled by a mains borne transmission system, the system can be installed, in some cases, using the existing store wiring.

Brief Description of the Drawings The invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic plan view of a system according to the invention; Figures 2, 3 and 4 show a display unit respectively from the front, the side, and when installed on some standard shelving; Figure 5 illustrates the method of ascertaining which transmitter units are in the range of a given display unit, in the cases of two display units; and Figures 6 and 7 illustrate how, using pulse code modulation techniques, an optical signal, such as an infra-red signal, can be so encoded as to transmit a binary code.

Description of the Preferred Embodiment The system shown in Figure 1 is installed in, for example, a supermarket, and includes an array of control modules 1.

Each control module 1 is ceiling mounted in a position directly above an aisle defined by the supermarket shelving, and includes a transmitter unit and a receiver unit which enable the control module 1 to transmit and receive infra-red signals.

The control modules 1 are controlled by a point of sale (POS) terminal controller interface unit 2, which is connected to the control modules 1 via the existing mains wiring of the supermarket. The interface unit 2 communicates with the control modules 1 using a mains borne communication link, which enables instructions to be sent to and from the control modules 1 through the mains wiring. Mains borne communication has been used for some time in various applications, and a number of operational techniques have been developed.

The present system makes use of the National Semiconductor Corporation BI-LINE current carrier networking system, and the LM1893 integrated circuit.

The BI-LINE system makes use of frequency modulated signals introduced into the mains electrical system. The modulation technique is commonly known as frequency shift keying (FSK).

The system also uses a protocol, known as BAT, to reduce the occurrence of misinterpretation of data relayed via the mains borne communication link. Details of the BI-LINE system are available by reference to the National Semiconductor Corporation publication literature number 57005.

The control modules 1 are so positioned that the transmitter unit can transmit infra-red control signals to a plurality of individual display units 3 which are mounted on the supermarket shelving. Referring to Figures 2, 3 and 4, each unit 3 includes a protuberance 4 which projects from the back of the unit 3, and enables the unit 3 to be slideably mounted on the tracks provided on the front of standard shelving.

Each display unit 3 includes a LCD display 5 which, in use, displays the price of the product provided on the shelving adjacent the display unit 3. Identification of the product to which the price refers is facilitated by three arrows 6 which are so positioned, in use, as to point to the product in question. Additionally, or alternatively, the LCD display 5 may be a dot matrix display which identifies the products in question by name as well as displaying their price.

Each control unit 3 includes an infra-red receiver 7 which receives, in use, infra-red control signals from a transmitter unit of a ceiling module 1. Each display unit 3 can also transmit infra-red confirmation signals to a receiver of a control module 1, using an infra-red transmitter 8.

The power needed to operate the display module is derived from an internal re-chargeable battery (not shown) which is connected to the output from an array of solar cells 9.

The solar cells are mounted on the face of the display unit, and typically have an output in the region of 7 mA at 4V.

Since this power level will be inadequate to operate the infrared transmitter 8, the display unit 3 includes an energy storage capacitor (not shown) which is so connected as to be charged from the re-chargeable battery, and, in use, discharges to provide the necessary power peaks to operate the transmitter 8.

During night time hours, when the supermarket lights are extinguished, the display is turned off to conserve power.

This power supply system may be derived from existing solar technology. However, the solar cells 9 are custom made to fit the space available on the face of the display unit 3.

Coding of the infra-red control signals from the control modules 1 to the display units 3, and of the infra-red confirmation signals from the display units 3 to the control modules 1, will be based on the time relationship between pulses of infra-red light. This form of coding is commonly known as pulse code modulation; using a basic transmitted pulse length of T-microseconds, the binary value of each pulse (1 or 0) will be decided by the space between two successive pulses, a space of XT being equal to binary 1 and YT to binary 0 (where the values of X, Y and T are selected in accordance with the response characteristics of the infra-red transmitters and receivers). An example of these relationhips is illustrated in Figure 7.

The control signals will contain display module address codes and data messages which will be grouped in standardised word lengths (hereinafter called long words and short words), each comprising a number of binary bits dependent on the type of information being conveyed. Examples of word format are given in Figure 6.

Each word will be separated by a pre-defined interword gap to enable the display units 3 to distinguish between respective words. Each word will be transmitted twice in differing bit ordrs and both transmissions must be received within a finite time to be valid. The display unit 3 must respond with a confirming code before a new word is transmitted.

A complete sequence of data will be terminated with a check code word based on the sum of all the foregoing data bits, and must be recognised as valid for the display unit 3 to update and respond with a confirming message to the control module.

If during a transmission sequence an expected display unit 3 response is not obtained within a pre-determined time and/or number of attempts, the data transmitted in the control signal will be ignored, and the display unit 3 will not be updated.

The control signal will be decoded in the following way.

Since only two word lengths will be used and long words are used only once in any sequence, display module decoders know that when a long word has been decoded, the remainder of a message will consist of a number of short words defined by the segment part of the address code.

Words will be decoded by causing the first pulse to be received to open two windows. The first of these will open after an interval representing a binary 1, the second after an interval representing a binary 0.

If a signal is received whilst the first window Is open, a binary value of 1 is assumed, and if a signal is received whilst the second window is open, a binary value of 0 is assumed. In this way, one digit of a binary signal can be transmitted. Following the receipt of the second pulse, two more windows will be generated, and the process is repeated until all of the expected pulses (corresponding to the expected number of digits, or bits, of the binary signal) have been received.

When all of the expected bits have been received, and if the first and second halves of the word match, the display unit 3 will respond by transmitting a confirmation signal, informing the control module 1 that the next word can be sent.

As each 1 and 0 bit in a complete message is received, it will be counted. The value counted will be compared with the binary value of the two final words in the message which represent the number of bits transmitted. The values must agree before the display unit 3 can update its display and transmit the confirming response to the control module 1 When a ceiling mounted control module 1 transmits a control signal, it is likely that it will be reflected from numerous objects below. Since the transmitter unit of the control module 1 points downwards, the reflections will be in an upward direction, and will not therefore be received by the receivers 7, each of which faces upwards when in its normally intended attitude of use (as can be seen from Figure 4).

In order to avoid spurious reflected signals being received by the (downward facing) receivers in the control modules 1, each of the receivers will be desensitized for a period of time after the last transmission pulse in any sequence. If, for example, it is calculated that a spurious reflection must travel 30 metres before arriving back at the control module 1, the desensitising of its receiver for at least 100 nano seconds will prevent the reflection being misinterpreted as part of the confirmation response from a display unit 3.

Immediately following the installation or revision of an existing installation of the system, a signal carrying a binary encoded address to a particular display unit 3 is transmitted from each control module 1 in sequence. Each control module 1 obtaining a response from the address display unit 3 signals this fact to the control system which then maps which control modules 1 are able to communicate with a particular display unit 3. This mapping sequence will continue until all display units 3 are mapped. Part of this sequence is illustrated in Figure 5.

Following the mapping sequence, further addressing of display units 3 will initially be from appropriate control modules 1 i.e. the control modules 1 lying in the transmission range of the display unit 3 in question. However, if this does not result in any confirmation signal being received after a predetermined time and/or number of attempts, the control signal addressed to that particular unit 3 will be transmitted by each of the control modules 1 in sequence.

IMPLEMENTATION OF THE INFRA-RED COMMUNICATION CHANNEL Numerous commonly available integrated circuit are available to implement the infra-red communications channel. Examples of these are: Transmitter SFH485P, SFH487P, TSUS5402, CQY99.

Transmitter Driver Any appropriate switching transistor Receiver BPW41N, BP104, BPW34, TIL100 Receiver Pulse Shaper SL486, TCA440

Claims (7)

1. CLAIMS: 1. An information display system of the kind in which information is displayed on a plurality of individual display units, each of which can receive display pattern control signals addressed thereto from one or more transmitter units remote therefrom, the system being characterised in that the control signals are optical signals.
2. 2. An information display system according to Claim 1, in which the optical signals are infra-red signals.
3. 3. An information display system according to Claim 2, in which each display unit includes a transmitter for optical signals, enabling each display unit to transmit a signal, confirming that, for example, a control signal to that display unit has been received, or that the instructions contained in the control signal have been executed.
4. 4. An information display unit according to Claim 3, which is used in a price display system, which display unit includes a solar cell so connected to the rest of the display unit that the, or part of the energy needed to operate the display unit, is provided by the output of the solar cell.
5. 5. An information display unit according to any of the preceding Claims, in which the system includes a plurality of transmitter units for the control signals, each transmitter being connected to the mains electrical supply.
6. 6. An information display unit according to Claim 5 in which there are a plurality of transmitter units, the system including the feature that the control signal addressed to a particular display unit is transmitted only by the transmitting unit (or transmitting units) in the range of the display unit.
7. 7. An information display unit as described herein with reference to and as illustrated in the accompanying drawings.