# Another One-button Dynamic Mode for Dasher: Two-click mode'

## David J C MacKay

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, presented in \cite{OneButton} and \cite{ButtonDasher2007} and included in Dasher 4 (released 2006) under the name one-button dynamic mode'. This note describes {\em{another}\/} design for a one-button version of Dasher, which is expected to be more user-friendly. I'll call this `two-click mode' because the principal gesture made for each navigation action is a pair of clicks.