Switch site

Also called Switch placement, Access site, Control site

Finding the one movement a person can make on purpose, a hundred times a day, without pain or fatigue. Everything else in switch access rests on it.

What it is

The switch site is the part of the body, and the movement of it, that will operate the switch. A hand pressing down. A head turning left. A knee lifting. A foot pressing. A cheek twitching. A puff of air. Choosing it is the single most consequential decision in switch access, and it is the one most often made by whoever happened to be in the room with a spare hand switch.

It is a decision about reliability, not about strength or size. The best site is the one the person controls, not the one that moves most.

Who it can help

Everyone who is going to use a switch, and everyone whose switch use is failing. A person who "can't do scanning" very often has the wrong site. A person whose accuracy collapses in the afternoon often has a site that fatigues.

It is worth reassessing at every change: a new wheelchair, a growth spurt, a change in tone, a progression of illness, a new medication. In motor neurone disease the site may need to move every few months, and planning the next site before the current one fails is what keeps a voice uninterrupted.

How it works

An assessment tries candidate movements against a short list of tests. Can the person make it on request, and stop it on request? Can they make it ten times in a row? Is it still there after a minute of rest and after ten minutes of use? Does it trigger unwanted movement elsewhere (an extensor spasm, a startle)? Does it hurt? Does it interfere with sitting, breathing, eating or looking at the screen?

Hands are tried first, then head, then feet and knees, then the smaller movements: eyebrow, cheek, chin, breath. The switch is then chosen to match the movement's force and range (see types of switch) and mounted so it is always in the same place (see switch mounting). A second site, if one exists, opens up two-switch scanning and gives a backup.

Getting started

Spend a week noticing. When the person is relaxed, engaged and wanting something, which part of them moves first? When they are tired? Video thirty seconds of each. That footage is worth more than any form.

Then, with a switch and a toy or music player, test the top two candidates for a few days each, at three times of day. Log presses attempted, presses landed, and false presses. Keep the switch in exactly the same position each time, or you are testing the mounting, not the site.

Where to get help

Site assessment is done by an occupational therapist, physiotherapist and speech and language therapist together; ask for it as part of an AAC assessment. The ACE Centre publishes a free switch assessment framework, and the Barnsley Assistive Technology Team and other specialised AAC services do this work for people with the most complex needs.