Knowledge base

How to speed up switch input in The Grid 2

This article discusses how to use switch input. For help on setting up switch input see ‘Access methods: Switches’.

Despite the emergence of exciting new technologies such as eye tracking and speech recognition, a large number of people with disabilities are dependant on the use of switches for communication, both verbal and written. Using a switch in this way can be a slow and frustrating business, and much thought has gone into ways of improving the rate of input with switch systems.

Grid layout

The layout of the alphabet on a grid is a crucial factor for scanning speed. Depending upon the user, an alphabetic or qwerty layout may be required. For users with poor sight or no sight, layouts for audible scanning can be chosen, and for advanced users they letters can be arranged by how frequently they are used. For some examples of keyboard grid layouts, see this article.

Word completion

Word completion, or prediction, is a very common way to speed up switch input. As words are typed, part of the grid is automatically populated with suggestions for the word being typed. Selecting these will save the user a large number of switch presses.

Block, row and column scanning

The scanning of a grid can be sped up by narrowing down the cells to be selected. Block scanning divides the grid into 4 large groups of cells, and the user selects one of these before continuing with the scan. Row-column (or column-row) scanning allow the user to select a row (or column), and then a cell within that row (or column).

Extra functions from a second switch

If a user can operate additional switches, these can be used to access additional functions. You can also set up a ‘virtual’ second switch that operates when the user holds a switch down for a long time.

Cancelling a scan

If the wrong block, row or column has been selected then the user will be trapped with a choice of cells that does not include the desired cell.
It is possible to set up a switch to operate as a cancel button, if the user can manage a second switch. If this option is not available then you can set a maximum nuber of times for the scan to loop around before it cancels itself automatically.

Reverse scan

A frequent error is to miss a cell by failing to press the switch in time. When this happens, it is very annoying to have to watch the highlight moving further away from the cell that you wanted, or cancel the scan and start again. A second switch can be used to reverse the scan, allowing the cell to be reselected.

Critical overscan

Some users with a gross tremor will find that no matter how ready they are to press the switch when the scan comes up, their reactions are frequently delayed, and the switch is pressed too late. It is also common for such users to find it difficult to hold down a switch until the desired cell is reached. The result is often a painfully slow automatic scan. This technique works by ensuring that only the cells close to the target are scanned slowly. When the scan starts, it moves forward at a fairly high speed, and the user tries to hit the switch again when the target cell is reached. Depending on the speed setting, the highlight will have moved two or three cells beyond the target, but the scan automatically goes into reverse at a much lower speed. The user can then choose one of the cells at a pace they can manage.

More forgiving switch modes

The use of a delay before the software processes a selection is another way of making a switch input more effective for people with poor motor control. This is particularly effective for people using switches by holding them down until the target is reached. One example of this is using two head switches for row/column scanning. One switch is used to advance from row to row, while the other is used to move along the row. When one of the switches is held down, the scan moves in the appropriate direction at predetermined rate. When the switches are released, nothing will happen until a time out has occurred. In this way, if the user should accidentally release the switches at the wrong time, there is a chance to continue the scan by pressing one of the switches again.