Abstract: A communications system distributes code word pairs within the audio of a television or radio program or the like. Each pair of code words includes an ID code word that is the same for a given program and a synchronization code word that is unique within the program. A portable user device is able to synchronize itself to the program using the embedded synchronization code words.

Abstract: A communications system distributes code word pairs within the audio of a television or radio program or the like. Each pair of code words includes an ID code word that is the same for a given program and a synchronization code word that is unique within the program. A portable user device is able to synchronize itself to the program using the embedded synchronization code words.

Abstract: A communications system distributes code word pairs within the audio of a television or radio program or the like. Each pair of code words includes an ID code word that is the same for a given program and a synchronization code word that is unique within the program. A portable user device is able to synchronize itself to the program using the embedded synchronization code words.

Abstract: A communications system distributes code word pairs within the audio of a television or radio program or the like. Each pair of code words includes an ID code word that is the same for a given program and a synchronization code word that is unique within the program. A portable user device is able to synchronize itself to the program using the embedded synchronization code words.

Abstract: A data hiding system is described for hiding data within an audio signal. The system can be used for watermarking, data communications, audience surveying etc. The system hides data in an audio signal by adding artificial echoes whose polarity varies with the data to be hidden. In one embodiment, each data value is represented by a positive and a negative echo having different delays. A receiver can then remove the effects of natural echoes and/or periodicities in the audio signal by differencing measurements obtained at the different delays.

Abstract: A captioning system is provided for providing captions for audio and/or video presentations. The captioning system can be used to provide text captions or audio descriptions of a video presentation. A user device is provided for the captioning system having a receiver operable to receive the captions together with synchronization information and a caption output circuit which is operable to output the captions at the appropriate timings defined by the synchronization information. The user device is preferably a portable hand-held device such as a mobile telephone, PDA or the like.

Abstract: There is described a communication system in which data is received by and/or transmitted to a telecommunications apparatus using an acoustic data channel. In embodiments, the data is encoded within the audio track of a media broadcast or other public broadcast. The invention has particular, but not exclusive, relevance to a cellular communication system. There are also described acoustic position detection systems for determining the position of a telecommunications apparatus.

Abstract: A data hiding system is described for hiding data within an audio signal. The system can be used for watermarking, data communications, audience surveying etc. The system hides data in an audio signal by adding artificial echoes whose polarity varies with the data to be hidden. In one embodiment, each data value is represented by a positive and a negative echo having different delays. A receiver can then remove the effects of natural echoes and/or periodicities in the audio signal by differencing measurements obtained at the different delays.

Abstract: A data hiding system is described for hiding data within an audio signal. The system can be used for watermarking, data communications, audience surveying etc. The system hides data in an audio signal by adding artificial echoes whose polarity varies with the data to be hidden. In one embodiment, each data value is represented by a positive and a negative echo having different delays. A receiver can then remove the effects of natural echoes and/or periodicities in the audio signal by differencing measurements obtained at the different delays.

Abstract: There is described a communication system in which data is received by and/or transmitted to a telecommunications apparatus using an acoustic data channel. In embodiments, the data is encoded within the audio track of a media broadcast or other public broadcast. The invention has particular, but not exclusive, relevance to a cellular communication system. There are also described acoustic position detection systems for determining the position of a telecommunications apparatus.

Abstract: There is described a communication system in which data is received by and/or transmitted to a telecommunications apparatus using an acoustic data channel. In embodiments, the data is encoded within the audio track of a media broadcast or other public broadcast. The invention has particular, but not exclusive, relevance to a cellular communication system. There are also described acoustic position detection systems for determining the position of a telecommunications apparatus.

Abstract: A number of encoders for encoding a data signal within an audio signal are provided. In some of the encoders, the audio signal is separated into a tonal part, and a residual part, and the data signal is shaped based on the residual part. In other encoders, the data signal is separated into a tonal part and a residual part, and the data signal is combined with the audio signal independence upon the residual part. In other encoders, the rate at which the data is encoded within the audio signal is varied in dependence upon the audio signal. There are also described various decoders associated with the described encoders.

Abstract: There is described a number of encoders for encoding a data signal within an audio signal. In some of the encoders, the audio signal is separated into a tonal part and a residual part, and the data signal is shaped based on the residual part. In other encoders, the data signal is separated into a tonal part and a residual part, and the data signal is combined with the audio signal independence upon the residual part. In other encoders, the rate at which the data is encoded within the audio signal is varied in dependence upon the audio signal. There are also described various decoders associated with the described encoders.

Abstract: A position determining system in which a mobile tag having an unknown position is tracked in space over time. In use, the mobile tag either transmits or receives signals including a pair of tones at different frequencies from a number of base stations having known locations. The phase of each of the received signals is then measured and the measured phases are then passed to a processing unit which determines the position of the tag at the time of the transmission of the signals on the basis of the difference between the measured phases of the two tones. In one embodiment, this system is combined with a conventional phase-based position measurement which is derived from phase measurements of similar tones transmitted between the mobile tag and different base stations.

Abstract: A position determining system in which a mobile tag having an unknown position is tracked in space over time. In use, the mobile tag either transmits or receives signals including a pair of tones at different frequencies from a number of base stations having known locations. The phase of each of the received signals is then measured and the measured phases are then passed to a processing unit which determines the position of the tag at the time of the transmission of the signals on the basis of the difference between the measured phases of the two tones. In one embodiment, this system is combined with a conventional phase-based position measurement which is derived from phase measurements of similar tones transmitted between the mobile tag and different base stations.

Abstract: There is described a communication system in which data is received by and/or transmitted to a telecomunications apparatus using an acoustic data channel. In embodiments, The data is encoded within the audio track of a media broadcast or other public broadcast. The invention has particular, but not exclusive, relevance to a cellular communication system. There are also described acoustic position detection systems for determining the position of a telecomunications apparatus.