Welcome to the Aidis Trust blog. Here you’ll find our posts on assistive technology that are meant to inform and encourage discussion. Feel free to join in!

Switches explained


As part of my latest insight into the world of Electronic Assistive Technology, I’ve decided to dip into the world of Switches. An alternative way for people with greatly reduced mobility and/or cognitive ability to access computers.

What is a switch?

OK, to many of us, the term switch has various meanings and to a number of you, here is another.

We all know of wall switches that turn lights and other electrical devices on and off and we also have computer network switches that allow multiple computers to be connected to one another though we aren’t talking about either of these applications.

A computer access switch can come in all shapes and sizes and can be activated in numerous ways, but essentially (and like a wall switch I suppose) they send an on or off signal to a computer. Every switch also has one other thing in common and that is that they need an interface to turn that on or off signal into a signal that a computer can recognise and work with. Commonly, this is done by plugging your switch into an adaptor that then either plugs into a USB port or sends a Bluetooth signal, telling your computer that a key or mouse button has been pressed.

Once this signal has been received by the computer, then a software program can work with that signal (key press, mouse button press) and work its wonders.

Types of switches

Switches can be placed into 2 categories – mechanical switches (ones that you have to physically press) and non-mechanical switches.

The mechanical switches come in all shapes and sizes, with the most common of these being in the shape of a 2.5inch diameter round button. There are, however, many alternative sizes of mechanical switches and also switches that can be bent, such as a leaf switch or wobble switch.

Non-mechanical switches tend to utilise sensors. Such as sound operated switches, that detect sounds and suck/puff switches that are activated by sucking or puffing air from the mouth into a straw.

A key consideration when using a switch is its placement – can the person with the mobility and/or cognitive disability access the switch.

Just to remind you, all these switches have one thing in common – they are either on or off and through an interface, the signal of a keyboard or mouse button being pressed or not is relayed to the computer.

What can be achieved through using a switch?

Most of the magic is produced in software that handles the switch’s signal. Through a technique called ‘scanning’, selections can be made from, say an on-screen keyboard or a custom set of selections such as a collection of program start-up icons. Think of a keyboard as being a collection of rows and columns. By pressing the switch, you can toggle through each row. Then, by pressing the switch again, you will toggle across that row, highlighting each key in turn. Press the switch again and that key is selected and placed into a Word document, email message or whatever your switch program is interfacing with. 

Alternatively, the switch can be used to produce simple cause and effect tasks such as building stages of a picture. Other, rather important uses include accessing communication software.

So, through using a switch, you can do almost any task that people do using a computer. From navigating around websites, emailing, skyping, spreadsheets and much more.

The rule of thumb is that since the speed of accessing a computer is greatly reduced when using switches, software such as arcade style games, don’t tend to be practical or indeed possible.

A comforting thought

Switches, as with many areas of Electronic Assistive Technology, can seem daunting and complicated. To an extent they are. Though this is mainly down to need flexibility, to have enough range in both their type and their settings, to cater for the vast array of disabilities traits that they can help overcome.

The hardest part is finding the best fit. Once this is achieved, it’s much more straight forward. Our charity also exists to help people overcome this daunting mountain of information, and only provide people with the information that they need as well as offering training, specific to their needs, not the needs of the many.

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