Pricing display system

Claim 1

A system comprising a central unit and a plurality of display modules each adapted to show on a display device information received from said central unit, for displaying prices in a store, wherein said central unit comprises transmission means including a current loop fed with a low-frequency signal modulated according to display and control information to be transmitted, said transmission means for transmitting the modulated low-frequency signal to the display modules, and further comprising, in each display module, a battery, a reception circuit, a reception antenna electromagnetically coupled to said current loop and means for activating the reception circuit at predetermined periods and for a limited duration, wherein each transmission of information by said central unit is preceded by the transmission of a reactivation signal which, when detected by said reception circuit during a period of time in which said reception circuit is active, causes it to be held in the active state for at least part of the duration for which said information is transmitted, said system further comprising at least one portable terminal comprising means for generating initialization information to be transmitted to display modules and means for transmitting said initialization information by means of a second current loop fed with a low-frequency signal modulated according to said initialization information, said initialization information being transmitted to a display module by close electromagnetic coupling between said second current loop and said antenna of the display module, wherein the magnitude of the electromagnetic field received by a display module from said first loop is substantially lower than the magnitude of the electromagnetic field received from said second loop when said portable terminal is brought close to said display module, and each display module comprises field amplitude detection means for differentiating between remote transmission of display or control information from the central unit and proximity transmission of initialization information from said portable terminal; wherein said field amplitude detection means are activated at a second period shorter than said first activation period.

Claim 2

A system comprising a central unit and a plurality of display modules each adapted to show on a display device information received from said central unit, for displaying prices in a store, wherein said central unit comprises transmission means including a current loop fed with a low-frequency signal modulated according to display and control information to be transmitted, said transmission means for transmitting the modulated low-frequency signal to the display modules, and further comprising, in each display module, a battery, a reception circuit, a reception antenna electromagnetically coupled to said current loop and means for activating the reception circuit at predetermined periods and for a limited duration, wherein each transmission of information by said central unit is preceded by the transmission of a reactivation signal which, when detected by said reception circuit during a period of time in which said reception circuit is active, causes it to be held in the active state for at least part of the duration for which said information is transmitted, said system further comprising at least one portable terminal comprising means for generating initialization information to be transmitted to display modules and means for transmitting said initialization information by means of a second current loop fed with a low-frequency signal modulated according to said initialization information, said initialization information being transmitted to a display module by close electromagnetic coupling between said second current loop and said antenna of the display module, wherein the magnitude of the electromagnetic field received by a display module from said first loop is substantially lower than the magnitude of the electromagnetic field received from said second loop when said portable terminal is brought close to said display module, and each display module comprises field amplitude detection means for differentiating between remote transmission of display or control information from the central unit and proximity transmission of initialization information from said portable terminal; wherein said field amplitude detection means are activated at a second period shorter than said first activation period.