Row-Column Scanning

The most widely used single-switch selection method for augmentative and alternative communication (AAC) devices and on-screen keyboards. Options are arranged in a two-dimensional grid, and the interface sequentially highlights each row. When the user clicks their switch, the highlighted row is selected, and the interface then scans through individual columns within that row. A second click selects the desired option. While RCS is efficient for grid-based layouts, it has limitations: options must be arranged in a strict grid, a single mistimed click selects the wrong row or column, and dead-time waiting for scanning increases with more options.