Page 150 - Handbook of Electronic Assistive Technology

138 HANDBOOK OF ELECTRONIC ASSISTIVE TECHNOLOGY

FIGURE 5-24 A selection of assistive switches�

• Feedback (whether the switch moves, by how much; auditory feedback; haptic
feedback).
• Mounting options.

Mechanical Switches
The most common type of switch is electromechanical and a very wide range of shapes,
sizes and types are available (Fig. 5-24). Assistive technology switches are usually termi-
nated with a 3.5 mm jack plug.
Mechanical switches provide feedback – perhaps an audible click or a beep. This feed-
back can make the switch easier to use. Many mechanical switches provide tactile feed-
back when activated, and this can help the operator locate and use the switch.
These factors may affect how well a particular mechanical switch works for a particular
individual. A user with limited strength might prefer a switch which needs minimal pres-
sure and activation travel, while another user with poor proprioception might be helped
with a larger, more robust switch that offers greater feedback.
Switches are commonly placed on a tray or desk and accessed using a finger or
hand. Some users experience difficulty lifting their hand up and then lowering it to
activate the switch, and may achieve greater success when the switch is mounted ver-
tically and activated by a lateral movement, or when a flat switch is mounted flush
with the table surface (e.g., a touch switch) enabling small wrist rotation movements
to activate the switch.

Switch Comfort
Switches accessed by head or cheek can be uncomfortable – the switch is typically manu-
factured from hard plastic, and users with athetoid movements can strike the switch with