A demonstration of the 'halving' (also called scan-direct) method of switch access. This access method is a 'coded' method - each switch represents half of the screen (e.g. red switch =left, blue switch = right) and pressing a switch selects the corresponding side of the screen. This can offer a potentially quick method of access, but also one that can be learnt - since the switch presses are always the same. It would be of most benefit to people who have no problems with repeated switch presses and have the ability to learn the motor planning to make the method automatic.
This grid demonstrates halving as an access method. In addition, halving is implemented in a different way in this demonstration bundle .
What is halving? Halving is a coded method of switch access - each switch represents half of the screen (e.g. red switch =left, blue switch = right) and pressing a switch selects the corresponding side of the screen. The number of presses is directly linked to the size of the grid and is always constant. For two switches, the following table shows the number of presses for a certain grid size (those of you who remember their GCSE maths will remember this as an exponential series):Presses grid size (Cells) Grid layout 1 1 1X1 2 4 2x2 3 8 2*4 4 16 3x3, 4x4 5 32 5x5, 8x4 6 64 6x6 7 128 7x7 -> 11x11, 16x8, 8 256 12x12 -> 16x16
Why halving? There is no research on this that I can find, however it is likely that halving would be of most benefit to people who have no problems with repeated switch presses and have the ability to learn the motor planning to make the method automatic. In addition, the method does not rely on timing, so people who have problems with the timing element of auto-scan might also benefit. Notes: This bundle uses 2-switch halving, you can also use 4-switch quatering (look in the user-settings, input options) This bundle is setup with F1&F2 as the switches, you can obviously use normal switches if you like (look in the user-settings, input options). Pointer input is turned off, so to get it to do something, press F1 or F2 on the keyboard! The bundle
is also setup to use F1 or F2 as pretend switches - to change this to
normal switches go to Edit->User Settings, Input Settings ->
Switch Settings -> Connection. In addition - note, you should hear something, if you don't - go to
Edit->User Settings, Speech Settings -> Public Voice.
Enjoy.
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Halving Demo
