Page 175 - Handbook of Electronic Assistive Technology

Chapter 6 • Environmental Control 163

Multiple-Switch Input
The extent of control can also be increased through availability of a greater number of
access inputs, although most conventional EC devices have been limited to two-switch
input. The four orthogonal directions, as discrete cursor buttons or the directions of a joy-
stick, have been utilised to navigate around selection menus or for each to have separate
access functions.

Multidirectional – Proportional Input
The term proportional input is typically applied to input devices such as a joystick. The
proportionality of input signal relates to the direction it is deflected to and the amount
or time of that deflection. With EC, there are few instances where the appliance being
controlled has variable states. Potential examples are the dimming of lighting and move-
ment of powered beds or chairs. However, control of these is adequately achieved through
single-switch scanning, where a repeated control signal continues to be transmitted for
the duration of switch activation. Bed movement is curtailed by an automatically timed
cut-off to ensure the safety of the user.
Multidirectional and proportional controls are of significant benefit as an input means
for the computer-based EC units and especially those with computer application func-
tions, where they can provide the equivalent of a ‘mouse movement’.

Speech Recognition Input
Recognition of spoken commands from the user has been much sought after as an
access method for EC, especially for those with no upper limb or other means of move-
ment access. However, the availability of such products and the reliability of recognition
have until recently been limited (Judge et al., 2009). This is largely because of the size of
computer processing capacity required to run the recognition algorithms in real time,
compared to that available in circuitry capable of being battery powered and therefore
suitable for a portable device. This resulted in devices utilising limited command word
sets for recognition. They were also found to be suitable only for users who are able to
articulate speech clearly and consistently and have sufficient cognition to be tolerant
of the level of error in recognition (Judge et al., 2009). In contrast, speech recognition
has developed as a reliable and versatile means of access to computers, where there
is sufficient processor power available to run the algorithm programs effectively. Such
means may also be used in conjunction with a wireless microphone/headset to provide
a remote means of EC within the home, with appliance control transmitters connected
to or driven by the computer. As compact personal computers with sufficient process-
ing power become available, then these have the potential to provide a portable device
with integral speech recognition.
However, much recent technological development has been focused on providing high-
quality speech recognition via internet connection to utilise computer processor resources
‘in the cloud’. Examples are Siri for iOS, Google for Android and Cortana for Windows
smart devices, and those in home hubs (Amazon Echo, Google Home, Apple Home).