Signalling system
First Claim
1. A signalling system, comprising:
- a first signalling device comprising;
i) an input terminal for receiving electrical message data having a power spectrum which lies substantially over a first bandwidth;
ii) means for spreading the power spectrum of the message data substantially over a second bandwidth which is greater than said first bandwidth and which extends over a frequency band which is audible to humans; and
iii) means for converting the data output by said spreading means into corresponding acoustic signals and for transmitting the acoustic signals into the atmosphere; and
a second signalling device located, in use, at a distance from the first signalling device and comprising;
i) means for receiving acoustic signals from the atmosphere and for converting the received acoustic signals into corresponding electrical signals;
ii) means for despreading the power spectrum of the received signals; and
iii) means for regenerating the message data transmitted by said first signalling device from the despread signals output by said despreading means;
wherein, in use, said first signalling device is operable to transmit said acoustic signals at a power level which is chosen in dependence upon the distance between said first and second signalling devices, so that the power level of the transmitted acoustic signals at the second signalling device is below the ambient noise level and therefore inaudible to humans in the vicinity of the second signalling device.
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Accused Products
Abstract
A signalling system is provided which can be used to update the prices of goods which are electronically displayed on supermarket shelves (1). The signalling system comprises a first signalling device having an input terminal for receiving electrical message data received from a central computer system (5), a spread spectrum encoder for encoding the received message data and an electroacoustic converter (11) for converting the encoded data into corresponding acoustic signals and for transmitting the acoustic signals into a transmission medium. The signalling system also comprises a second signalling device (3) having means for receiving acoustic signals from said transmission medium and for converting the received acoustic signals into corrresponding electrical signals, a spread spectrum decoder for decoding the received signals and a message regenerator for regenerating the message data transmitted by the first signalling device from the signals output by the decoder.
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Citations
34 Claims
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1. A signalling system, comprising:
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a first signalling device comprising;
i) an input terminal for receiving electrical message data having a power spectrum which lies substantially over a first bandwidth;
ii) means for spreading the power spectrum of the message data substantially over a second bandwidth which is greater than said first bandwidth and which extends over a frequency band which is audible to humans; and
iii) means for converting the data output by said spreading means into corresponding acoustic signals and for transmitting the acoustic signals into the atmosphere; and
a second signalling device located, in use, at a distance from the first signalling device and comprising;
i) means for receiving acoustic signals from the atmosphere and for converting the received acoustic signals into corresponding electrical signals;
ii) means for despreading the power spectrum of the received signals; and
iii) means for regenerating the message data transmitted by said first signalling device from the despread signals output by said despreading means;
wherein, in use, said first signalling device is operable to transmit said acoustic signals at a power level which is chosen in dependence upon the distance between said first and second signalling devices, so that the power level of the transmitted acoustic signals at the second signalling device is below the ambient noise level and therefore inaudible to humans in the vicinity of the second signalling device. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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32. A signalling system comprising:
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a first signalling device comprising;
i) an input terminal for receiving electrical message data;
ii) means for encoding the electrical message data; and
iii) means for converting the encoded data output by said encoding means into corresponding acoustic signals and for transmitting the acoustic signals into a transmission medium;
a second signalling device located, in use, at a distance from said first signalling device and comprising;
(i) means for receiving acoustic signals from said transmission medium and for converting the received acoustic signals into corresponding electrical signals; and
ii) means for decoding the electrical signals in order to regenerate the message data transmitted by said first signalling device;
wherein said first signalling device is operable to transmit said acoustic signals in a frequency band which is audible to humans and is operable to transmit said acoustic signals at a power level which depends upon the distance between said first and second signalling devices, so that the power level of the transmitted acoustic signals at the second signalling device is below the ambient noise level and therefore inaudible to humans in the vicinity of the second signalling device. - View Dependent Claims (33)
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34. A method of communicating data, having a power spectrum which lies substantially over a first bandwidth, between a first signalling device and a second signalling device, the method comprising the steps of:
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at the first signalling device;
(i) spreading the power spectrum of the message data substantially over a second bandwidth which is greater than said first bandwidth and which extends over a frequency band which is audible to humans; and
(ii) converting the data output by said spreading step into corresponding acoustic signals and transmitting the acoustic signals into the atmosphere;
locating said second signalling device at a distance from said first signalling device; and
at the second signalling device;
(i) receiving said acoustic signals from the atmosphere and converting the received acoustic signals into corresponding electrical signals;
(ii) despreading the power spectrum of the received signals; and
(iii) regenerating the data transmitted by the first signalling device from the despread signals output by said despreading step;
wherein said first signalling device transmits said acoustic signals with a power level which is chosen in dependence upon the distance between the first and second signalling devices, so that the power level of the transmitted acoustic signal at the second signalling device is below the ambient noise level and therefore inaudible to humans in the vicinity of the second signalling device.
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Specification