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User Interfaces and Interface Transmission Technologies to Assistive Devices

When making products usable for all users, including elderly users and those with disabilities the Design for All concept should be followed. If this is not achievable, one solution that may be chosen is to offer alternative interfaces that permit the use of assistive devices to fill the gap between the user interface of the original device and the abilities of the user.


What is a user interface?

The user interface (or Human Computer Interface) is the means by which people - the users, interact with the system - a particular machine or device. The user interface provides means of:

A braille displayProducts, known as assistive devices, have been specifically designed for people who have disabilities. Assistive devices need to be used in cases when the input and output facilities of ICT devices are unable to match the abilities of specific users. It is therefore necessary to characterise the input media and their possible replacements in assistive devices in order to define the data that need to be transferred between ICT device and assistive device. Table 1 (below) describes standard input media and their possible replacements while Table 2 (below) lists the respective output media.

Table 1. ICT input media

ICT input media
Replacement assistive device / media
Keys (keyboards, keypads) Alternative keys with different characteristics (larger, softer, more space between keys)
QWERTY keypad
Voice input
Speech to text
Alternative keyboards
Touchpads
Voice input (microphone) Text to speech
Text
Pointing device
Pointing devices Text input
Speech input
Alternative pointing device (e.g. for use with tongue)
Cursor keys

Table 2. ICT output media

ICT output media
Replacement assistive device / media
Visual display Larger display
Display with colour conversion
Braille pad / Braille display
Speech / audio (screen reader)
Vibratory
Audio output Vibratory
Visual
Amplifier / attentuators
Transposers
Speech to text (possibly with Braille extension)

ICT device input requirements

The input required by ICT devices can be characterized by the way the information is entered into the device:

The minimum Man Machine Interface (MMI) necessary for input to an ICT device consists of a number of keys for text and command input as well as either a pointing device or a set of cursor keys to control the focus of the input.

ICT device output capabilities

The standard media for representing output on an ICT device are:

The minimum MMI necessary for the output from most ICT devices must be capable of presenting textual, graphical and state information using audio and visual output media

Who would benefit from standardised user interfaces?

A person with any disability will require assistive technology to use ICT equipment whenever they cannot operate the controls, obtain information from the device or understand how the device operates.

Elderly and disabled users would benefit from standardisation of the interfaces to ICT so that one
assistive device, e.g. a display for the presentation of information in large letters, could be used for the widest possible range of products from different manufacturers.

The manufacturers themselves would benefit by complying with European and international regulations if they offer a compatible interface, even if they leave the production of the
assistive devices to third party manufacturers.

Problems encountered by disabled people and the ageing population using non-standardised user interfaces

Blind and Partially Sighted

A blind or partially sighted person will encounter problems with tasks on an ICT device that requires the use of sight, especially if provision has not been made for screen text size and colour configurations.

Hearing impaired

A person with hearing loss will have difficulty in hearing speech commands or audible signals given on an ICT device.

Physically impaired

People with physical impairments may have difficulty in operating controls on a device, for example, a person with an impaired sense of touch may find it difficult to use a touch pad on a computer.

Cognitively impaired

Some people who have a cognitive impairment may find that they do not understand how the device operates, or understand icons, abbreviations and long sentences or instructions.

Ageing population

Some elderly people suffer from a failing memory which can affect their ability to recall and learn things and may lead to confusion, therefore, devices that require significant programming or re-programming may cause problems.

Interface transmission technologies

Information to be exchanged

In most cases the requirement for an assistive device is either to produce output from the ICT system in a different modality (e.g. to convert text on a screen to speech output) or to produce an enhanced version of the same modality (e.g. larger characters on a high contrast display). In other cases the requirement may be for the modification of characteristics of signals which are not usually under user control (e.g. requesting more time for crossing at pedestrian controlled traffic lights).

The table below indicates the types of information to be exchanged between an ICT system and an assistive device.

Assistive device/service
From ICT system to the assistive device
To the ICT system from the assistive device
Control & status
Text
Graphics
Audio
Video
Control & status
Text
Graphics
Audio
Video
Braille display
X
X
 
 
 
X
 
 
 
 
Tactual graphics display
X
X
X
 
 
X 
 
 
 
 
Synthetic speech display
X
X
 
 
 
X 
 
 
 
 
Enhanced visual display
X
X
X
 
 
X 
 
 
 
 
Keyboard / pointer
X 
 
 
 
 
X
X
X
 
 
Speech recognition
X
 
 
 
 
X
X
 
 
 
Hearing aid
X
 
 
X
 
 X
 
 
 
 
Tactile hearing aid
X 
 
 
X
 
X 
 
 
 
 
Alarm/monitor system
X 
 
 
X
X
X
 
 
 
 
Smart house
X
X
X
X
X
X
X
X
X
X
Navigation system
X
X
X
X
X
X
X
 
 
 

Wired technologies

An RS-232 interfaceRS-232

RS-232 is an interface designed in the 1960s for communication between a dumb ASCII terminal and a modem. For many years it was the standard interface to interconnect computers, terminals, printers, scanners, mice, etc.

RS-232 is very suitable for connecting assistive data devices. However, it is not suitable for voice. Simplicity is the big advantage of RS-232.

Plain analogue audio

The simplest way of connecting audio devices is to do it with a plain analogue one-directional 2-wire interface constituting out of signal and ground. A bi-directional interface would be two one directional interfaces, where the ground wire could be common.

Video

Depending on the requirements, the choices for video transmission are:

USB plugUSB

USB is an interface used for connecting up-to 127 (slave) devices to a single host (master). The physical connection is a tiered star topology. The logical connection is point-to-point.

A typical USB configuration is a PC acting as a host (master). The host initiates all data transfers. Typically each device has a corresponding device driver at the host, which communicates with the device driver for the USB host adapter, which in turn communicates with the USB physical layer.

Wireless technologies

The two most dominant wireless technologies for local area connections are WiFi and Bluetooth.

WiFi / IEEE 802.11 family

WiFi is the trade name for the popular wireless technology used in home networks, mobile phones, video games and other electronic devices that require some form of wireless networking capability. In particular, it covers the various IEEE 802.11 technologies.

IEEE 802.11 refers to a family of specifications developed by the IEEE for wireless LAN technology. IEEE 802.11 specifies an over-the-air interface between a wireless client and a base station or between two wireless clients.

The purpose of WiFi is to provide wireless access to digital content. This content may include applications, audio and visual media, Internet connectivity, or other data. WiFi generally makes access to information easier, as it can eliminate some of the physical restraints of wiring; this can be especially true for mobile devices.

Bluetooth

Bluetooth is a standard for wireless accessory connections. With the current specification, up to 7 slave devices can be set to communicate with a master device. The maximum range is 10m but the range can be extended to 100m with additional amplifiers. The primary application areas have been considered to be interconnecting mobile phones, computers and PDAs. Secondary applications include smart housing and CANs (car area networks).

DECT (Digital Enhanced Cordless Telecommunications )

A DECT cordless telephoneDECT is an ETSI standard for cordless telephony, developed in the 1990s. The standard is defined in the various parts of EN 300 175-1. The typical application for DECT is a base station connected to the public or a private telephony network. The base station communicates with a handset, after configuration and set-up.

DECT aims to provide speech transmission at a quality comparable to the wired telephony service. In addition to voice calls it supports some data services like SMS, circuit switched and packet switched data. The DECT standard guarantees interoperability between similar devices from different manufacturers.

IrDA

The Infrared Data Association (IrDA) defines physical specifications communications protocol standards for the short-range exchange of data over infrared light, for uses such as personal area networks (PANs).

The infra-red spectrum is unregulated world-wide which overcomes one problem faced by the radio-based systems, but has the disadvantage that it is directional and requires both ends to be in the same room. Another significant advantage is that it is available now and it is inexpensive. A problem is that the standards are not uniquely defined so equipment from one manufacturer is not always compatible with that of another.

Checklist for user interfaces

Recommendations

Displays

Touchscreens

According to Namahn (2000), touch sensitive areas or keys for users with no impairments, should be of a:

However, Colle & Hiszem (2004) recommend that:

Key size should be varied according to the size and use of the screen and the impairment type. For example, for one-handed thumb use of mobile handheld devices equipped with a touch-sensitive screen Parhi, Karlson and Bederson (2006) state that:

Audio output

Icons / Graphics

Keyboards / keypads

Basic ergonomic features
Localisation of keys
Identification of keys
Activating keys

According to the Nordic Cooperation on Disability (1998) the power to press a key should be:

Pointing devices

Legislation

Further information

Acknowledgements

 



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