Dasher's One-button Dynamic Mode -- Theory and Preliminary Results

David J C MacKay and Chris J. Ball

The arithmetic-coding-based communication system, Dasher, can be driven by a single switch. In \cite{MacKayButtons2004}, we proposed two versions of one-button Dasher, `static' and `dynamic', aimed at a theoretical model of a user who can click with timing precision g, and who requires a recovery time D between clicks. While developing and testing those two versions we invented a third way of using one button, which we present here. This new dynamic mode, is much simpler than the dynamic mode presented in \cite{MacKayButtons2004}, and has a direct theoretical connection to our model user. This paper explains the theory, and gives preliminary experimental results for a single user on a prototype implemented in Dasher 3 in July 2007. This method of driving Dasher has been included in Dasher 4 (released 2006) under the name `one-button dynamic mode'.

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