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: 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: 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.

Abstract: There is described a signalling device having a plurality of electro-optic elements and a lens system which is operable to receive a plurality of incoming free-space light beams from respective different light sources and direct the received light beams to respective ones of the electro-optic elements. The layout and/or shape of the electro-optic elements in the signalling device is adapted in accordance with a predetermined distribution of light sources. In this way, the number of electro-optic elements can be reduced. In an alternative embodiment, there is provided a signalling device having an electro-optic device, a plurality of lens systems having respective different fields of view, and a plurality of reflecting surfaces. Each reflecting surface is associated with a corresponding one of the plurality of lens systems, and the associated reflecting surface and lens system pairs are arranged so that the electro-optic device is provided in common to the plurality of lens systems.