Some software can be played just using the space bar or a few other keys on your computer's keyboard. This software can also be used with special switches, for children who are unable to use the keyboard. Switches for this kind of use come in all shapes and sizes.
To connect these switches to the computer you need a "switch interface". This is a little box with a cable that normally plugs into your computer's USB port. The switch interface has about 4 small round sockets. You plug your switches into these. Simple!
When you press a switch, the interface box makes the computer think that the space bar (or some other key) is being pressed. So if you run a storybook activity, where normally you would press the space bar to turn the pages, you can now use a switch to do the same. Interface boxes can be set to behave like different keyboard keys or even the mouse buttons.