Many people with severe physical or cognitive impairment use one or more switches to access computers. A switch is an assistive technology device that replaces the need to use a computer keyboard or a mouse.
Types of switch 
Switches come in a variety of shapes and sizes depending on the action used to activate them (such as sip-puff, pushing, pulling, pressing, blinking or squeezing). Switches also vary in their colour and aesthetics. For push or press switches, the amount of force required to operate them varies or in some cases can be adjusted. Some switches may only require a touch (not even a press), some may be designed to be kicked. A switch can be operated by almost any body part that is able to produce consistent and voluntary movement.
Connecting a switch 
What can be accomplished with a switch 
Switches can be suitable for people with cognitive difficulties, developmental delays and physical limitations. In the simplest use they are a clear and simple way to demonstrate action/reaction often referred to as cause and effect. In the more complex use they could be the means to control mobility or interact with the environnment. There are a variety of motivating switch activities that can be used to assess and develop a person's understanding of choice and timing.
Switches can be link to a variety of devices for example: Augmentative and Alternative Communication devices, switch adapted toys, switch interfaces for computer access, SMART Technology, sensory room equipment and environmental control devices
Switch types 
The smallest amount of interaction that can be provided with a switch is binary switch input as holding down the switch for a certain amount of time may be impossible for a sip and puff device or painful for someone with arthritis. Some users will prefer to use one switch, others will prefer to use two and sometimes more. For users who are using their switches to access simple activities an additional switch brings about an option of choice. It also allows two users to work collaboratively or to play against each other.
Considering multiple switch access is important for users accessing more advanced activities through switch access scanning. This is usually determined by their physical capabilities. A single switch requires less physical control and is usually less tiring to access but it reduces scanning options and usually leads to a slower rate of input. Single-switch scanning also requires much greater concentration. Two-switch scanning enables a range of scanning options including row and column, and overscan. These can greatly increase input rates and can make using a computer or electronic assistive device far more comfortable and efficient.
- adaptivePlay an organization that adapts toys and has a website full of interactive switch adapted toys for children with special needs.
- HelpKidzLearn a web site full of FREE games for young children and those with learning difficulties.
- Smile Rehab a commercial company who make SMART chairs and platforms
- Inclusive Technology are a commercial company who make many switch accessible products.
- Spectronics is a commercial company where many assistive switches and switch accessible products are available.
- IntelliTools Inc. partnered with Madentec to develop the IntelliSwitch: a wireless switch interface with five switch ports and two built-in switches. IntelliTools is also the creator of the IntelliKeys: a programmable membrane keyboard with two switch ports. Various switch accessible educational software products are also produced by IntelliTools.
- Marblesoft-Simtech is a commercial company whose line of inexpensive software focuses specifically on training single and dual switch use.
- The One Switch Organisation hosts nearly 100 free one switch games for PCs and utilities to play more. It also hosts D.I.Y. switch accessibility adaptation guides and more.
- QED Ltd are a commercial company who make and sell a wide range of switches. The website contains a comprehensive list of the types of currently switches available.