A switch is something that opens and closes to control the flow of electrical current. Most switches are open by default and close when activated, but a select few are closed by default and open when activated [1, 2]. A switch typically responds to a single, specific type of input, such as 
• Physical pressure • Air pressure • Tilt • Proximity • Eye blink • Muscle activity • Sound
During an assessment for switch access, the clinician’s responsibilities are to (1) identify the motor capabilities of the client that are within volitional control, (2) select a switch and an input method that are compatible with the client’s motor capabilities, and (3) adapt the environment (e.g., the position of the switch) to maximize the client’s performance . During an assessment, the clinician must find the best match between a type of switch and body site. Once a match is made, switch activation becomes a consistent motion and the relationship between the switch site and the consumer’s movement remains fixed .