Types of Switch Access

• Single switch direct response
• Single switch automatic timed scanning
• Intermediate two switch step scanning
• Two switch step scanning
      row-column, block, inverse, delay
• Encoding

This is the simplest form of switch use.  The switch in plugged into a toy, one message voice output communication device, or computer.  A single switch hit has a single action, such as turning a toy on, making something happen on the computer (e.g. build a puzzle one piece at a time, each time the switch it hit) or 'say' one message with the voice output communication aid (VOCA). 

See activities and programs for Single switch - DIRECT response

Developmentally, this is the simplest form of switch use.  This is a means of evaluating and training a very young or cognitively challenged individuals 'cause-effect' concept.  

One activation = one immediate response

A user may operate more than one switch, each with a single, direct response.  For example - a switch on the left might be connected to a single message "Turn the page"  and another switch on the right might be a repetitive phrase in the book.

With this type of scanning, a timed option cursor moves from one selection item to the next.  This is an automatic, timed movement (rate of movement set by user).  It can be a very fast movement, or extremely slow, continual movement from one item to the next.  As the option cursor lands on the desired item, a select is made by activating the switch.   

See activities and programs for Single switch - automatic TIMED scanning

It has characteristically been seen as the simplest and easiest to understand method of scanning for switch users. 

Years of experience and observing individuals with physical disabilities struggling with accuracy of a times response, controlling movement down to a fraction of a second, and dealing with the inordinate amounts of time involved in waiting for scans just to make a selection, tell us that single switch TIMED scanning is NOT an ideal method of input for many users.  

This type of scanning may be appropriate for some users, however, there are many other options for two switch scanning and coding systems which, in many cases, offer significantly better efficiency, accuracy and speed for input. 

In this type of switch access, one switch moves the option cursor / box / highlight from one selection item to the next.  The second switch selects the desired item or action as it is highlighted.  There is NO timing component to this apart from the users own speed of switch activation in moving the option cursor from item to item.  The user is under no pressure to activate the switch at any time.  All timing and movement is under the users control at all times.

Historically, most people have considered two switch scanning to be complex and difficult to understand and master.  

Certainly, the action of two physical movements and actions, can require more motor planning and concentration.  However, ultimately, with practice and motor learning, it is most likely that a well designed two switch system can become a well practiced, 'automatic' kinesthetic movement which requires less active thought and displays more automaticity of movement...   just as we all do when learning motor tasks that, with repetition, become automatic.