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Switches: Overview

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What switches are...

Switches are user input devices and generally work in an "On/Off" fashion, but this isn't true of all switches. Some switches operate in an analog manner. This simply means if you move the switch farther, you get a stronger output or response. This is a common feature on game controller pads, powered wheelchair (PWC) joystick controllers and dimmer switches for lighting. Switches can be wired or wireless, large or small, programmable, lighted, or color coded, and the list goes on.

Image:2292light switch1.jpg

An example of a simple switch is an ordinary household light switch.

Condition A: Lights On

Condition B: Lights Off

An example of a more complex switch is a sip and puff pneumatic switch activated by the users mouth. This type of device can be set up to, depending the strength of the sip or puff, switch the direction and/or speed at which a PWC can travel. Slow/fast forward; Slow/fast reverse.


Types of Switches in Assistive Technology

Through experimentation and innovation, numerous types of switches have been developed which assist us in all facets of life. Assistive technology is no different and has, in fact, spurred the creation of all sorts of switches to aid people with limited function. Since the technology often changes a link to more information can be found [here.]

Since the types of switches are so numerous, an attempt will be made here to focus more on the means of actuation then on the types of switches themselves, though examples will be given. Since the switches are actuators often connected to devices through interfaces, the uses become redundant in description. The idea is to choose the switch type best suited to the needs of the individual to perform a desired task.

Hand and/or Foot Operated Switches

These types of switches typically are made of banks of one or more individual switches in a switch box, or are an array of switches controlled by one actuator such as in a joystick control used on some PWCs. Examples types and uses are:

  • Toggle - e.g. on/off, mode selection A/B
  • Bump - e.g. bedside call switch, PWC control via head movement, mouse click
  • Pull Switches - e.g. lighting, emergency alert,
  • Button Switches - e.g. question response, on/off
  • Other types include: Motion Sensing, Grip switch, thumb switch, light touch, adjustable pressure, rocker, etc.

Mouth Operated Switches

These types of switches allow users with little or no hand/foot control to manipulate certain aspects of their surroundings, including themselves. Examples are:

  • Sip/puff - speed/direction of PWC movement, communication devices, computers
  • Other types are bite switches, tongue switches.

Muscle Controlled

There is also a host of switches created to be controlled by muscle contractions. These can be controlled by the electrical impulses generated to fire muscles, or by the motion of residual tissue moving over electrodes. ([EMG] These types of switches may be used to actuate a powered hand for an upper limb amputee. [Video]

Switch Interfaces

Switch interfaces are devices used to connect a switch to another device, like a computer. The interface may provide a direct link from the switch, or may convert the signal into a format usable by the receiving device. The interface may provide for more than one switch to be connected, or for switches of different types to be used in different locations to activate the same control. The type of interface is determined, much like the switch, by the desired action to be controlled.

Mounting Switches

Switch mounting methods and devices are as diverse as the switches themselves. Switches can be molded in place, attached with adhesives, positioned with adjustable or flexible racks, arms, headrests or brackets. [Mount] There are even padded pads which can sit on the lap with a switch mounted.

The location and positioning of a switch varies by person and need, and care must be taken to adjust to the individual if a functional outcome is to be obtained. For example, a person with paraplegia who can only move the head has no use of a PWC with hand controls only. However, a properly mounted and positioned head switch [Flopper Stopper] can give that individual a certain level of control and independence. Another example would be of a loose bump button sitting on a tabletop. If a person lacking fine motor controls attempted to use the button and knocked it to the floor, it would quickly become useless, but if the button were mounted in a manner where it could be 'bumped' without displacing it, that individual could repeatedly use the button as needed.

Switch Scanning

A method of making a selection (typically on a computer) by highlighting individual options sequentially. Switch Scanning System

[Disable Online - Switches] [Ablenet Inc.] [Ability Net - Switches]