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Screen Phones

Screen phoneThe inability to pick up the telephone and contact people is one of the frustrating aspects of having a hearing impairment. With some residual hearing there are amplified telephones with volume control. But with no hearing a screen phone becomes invaluable.

The number of facilities provided by the telephone has increased. Call management services such as those which inform the user about waiting calls or caller identity are now quite commonplace, as are many interactive services including banking and shopping services, automatic access to directory enquiries, train and airline timetables and access to the World Wide Web.

Screen phoneAccess to interactive telephone services relies on visual interaction with a telephone which incorporates a small screen and which uses multi-function "soft keys". Different labels appear on the screen immediately above these keys to indicate their functions; the functions can change during the course of an interaction, as different options appear on the main area of the screen.

Most models of screen phone often include a:

  • Base module
  • Voice communications module (corded or cordless handset and/or speakerphone)
  • Keypad
  • Screen display

Most low-end products use a very small LCD display and can provide the most basic access to limited Internet content such as text email or news.

Midrange products usually have a larger screen with a miniature keyboard and offer interactive email or news feeds from the Internet although web-browsing capabilities can be limited.

High-end products can consist of colour LCD screens with graphics and touch-screen capabilities. They also allow email and web browsing.

Traditional screen phones can be used to speak part of the call as usual but at the press of a button the caller's conversation can be presented back in words on a screen.

The appearance and functions are similar to a standard amplified phone but with a much larger screen and text that can be increased in size to make it easy to read. Answerphone messages can also be replayed on the display in text. 

Screen phones can be ideal for people who want to voice their call but can no longer hear the response and find textphones too complicated. Some screen phones can also be used like an amplified telephone and like a standard telephone.

Analog Display Services Interface (ADSI)

The ADSI (Analogue Display Services Interface) is a screen phone telephony standard that was defined by Bellcore in the USA in 1995. It works in conjunction with a screen-based telephone to provide the user with softkey access to custom calling features.

It allows for the running of simple interactive scripts, such as Call Waiting, an application that displays the name and number of an incoming call whilst a call is occuring. ADSI not only allows the phone to display the number for example, it will also have the ability to offer furtehr actions such as, switching to the new call, forwarding the new call to voice mail, putting the new caller on hold, playing a recorded message, or dropping the current call and switching to the new call.

Touch screen phones

As technology has progressed some major telephone manufacturers have produced smaller and more mobile telephones which incorporate screen facilities that respond to touch.

Touch screen phones utilise a mostly touch screen-based user interface for performing activities. Touchscreen mobile devices have become increasingly popular in the late 2000s following the successes of the iPhone. However, according to new research (Beaumont, 2009) mobile phone users are yet to be won over by the latest range of touch-screen devices, finding many handsets slow and difficult to use.


  • According to research from Strategy Analytics (Peters, 2008), touch screen phone shipments will reach 90 million units worldwide in 2009, accounting for 7 percent of total volumes

Problems encountered by disabled people and the ageing population using screen phones

Visually impaired

Screen based technologies such as screen phones are often designed to be self taught using hands-on exploration of the user interface, backed up with printed manufacturer's instructions. A great deal of information can also be communicated implicitly using visual clues, therefore providing a barrier for people who have visual impairments.

The size of the screen, screen resolution, availability of colours, fonts and font sizes will all have an impact on how blind and partially sighted users access a screen phone.

Patterned backgrounds or an image in the background of the screen reduces the legibility of the text for those who do have some sight. Flashing, scrolling or moving text can also create significant problems for people with low vision, as the reader's eyes have to move at the same time as focussing on the text.

The quality of audible cues, and particularly the quality of the speech synthesiser become very important. This is also true for users who have hearing impariments and those for whom the language is not their mother tongue.

Screenphone with receiver, keyboard and LCD displayPhysically impaired

The design of screen phones often assumes a degree of manual dexterity and hand-eye coordination which may be reduced or absent in those who have physical impairments.

Other physical problems (e.g. weak grip and hand tremors), can make lifting and holding a handset difficult and make keypad operation slow and inaccurate. These tasks may also be painful.

Positioning of the telephone and the means of access to it may be critical for those who use wheelchairs, wlking sticks or frames.

Cognitively impaired

People who have a learning disability such as dyslexia, may find difficulty in reading and deciphering text both on a keyboard and on a screen.

People with the specific condition called ‘photo-sensitive epilepsy’ may find that moving or flickering light can cause problems, and this can include screen phones. Only a minority of people with epilepsy are in fact photo-sensitive. For many others, the problems they experience while using a screen are not due to the movement, or “flicker”, of the screen image but rather to other causes such as eye strain and general stress.

Overly complicated installation or instruction manuals can also prove to be a challenge for some people with cognitive impairments.

Ageing population

Elderly people can experience a range of the problems mentioned above due to reduced physical, sensory or cognitive abilities that come with advancing age.

Checklist for screen phones


  • Menu systems should be helpful and logical
  • General layout of the phone, functions and interaction principles should be standardised for all devices


  • Good contrast with the background should be provided for text and graphics
  • There is provision for adequate, adjustable illumination of the LCD display whenever possible
  • Use back illumination of LCD screens whenever possible (a simple regulation of contrast or brightness is not sufficient)
  • Anti-glare provision to avoid reflections whenever possible
  • It is possible to tilt the display
  • Combinations of blue, green and violet should be avoided
  • Colour alone should not carry information
  • A line by line presentation is often preferable to a single line of scrolling text


  • The touchscreen should be shielded from sunlight
  • The screen should be angled towards the horizontal to provide arm/wrist support
  • The screen should be perpendicular to the line of sight
  • The text and background colour combination should have high contrast
  • Avoid shades of blue, green and violet for conveying information since they are problematic for older users
  • There should be no noticeable flicker on the screen
  • Structure the visual display layout so that the user can predict where to find required information and how to use it


  • Clear print fonts have a minimum type size of 12 point
  • There is clear letter spacing between each character
  • Kerning between specific characters is sufficient so as to ensure legibility
  • Avoid the use of italic fonts as they are more difficult and slower to read
  • Avoid patterned backgrounds for fonts
  • Ensure the font has both upper and lower case letters as it is easier to read text in upper and lower case than all capital letters
  • There is a system for enlarging text on the screen
  • Information should be presented in small amounts which can be easily retained


  • Good visual contrast between the keys and the body of the phone
  • Key tops should be convex or flat with a raised edge
  • Keys should be as large as possible without reducing the distance between the keys to less than half the key width
  • Ideally the keys should be internally illuminated, but the internal illumination should not reduce the legibility of the numbers in daylight
  • The visual markings on the keys should be high contrast, clear, and as large as is possible on the key top
  • Keys should be raised above the body of the phone (preferably by 5 mm)
  • There should be auditory and tactual feedback of key activation
  • There should be a tactual indication on the '5' key or on a QWERTY keyboard on the 'F' and 'J' keys
  • A voice mode selection that announces all key presses
  • An event/interrupt Interceptor intercepting data displayed on the screen and any key pressed

Audio output

  • There is an option to switch off verbal feedback when/if not required
  • There is an option to switch off non-speech sounds, if used
  • Voice warnings should be presented in a voice that is different from other voices that will be heard in the task situation
  • Maximise the intelligibility of the messages
  • Picture showing how the phrase can you recognise speech? can be heard as, can you wreck a nice beach?Make the voice as natural as possible so people are more likely to accept it
  • If the message is missed, it is beneficial for people to be able to replay it
  • If the message is familiar, the ability to interrupt the message would be beneficial for experienced users
  • Where the choice of messages is relatively limited, human voices are preferred because synthetic speech is less intelligible and less preferred
  • Use non-speech audio messages only for the purposes of alerting


  • AS/NZS 4277 (1995) Text Telecommunications - User interface requirements - For deaf people and people with hearing and speech disabilities
  • ETR 160 (1995) Human factors aspects of multimedia telecommunications
  • ETS 300 640 (1996) Human Factors (HF): Assignment of alphabetical letters to digits on standard telephone keypad arrays
  • ETSI ES 202 076 (2002) - Human Factors (HF); User Interfaces; Generic spoken command vocabulary for ICT devices and services
  • ETSI TR 101 806 (2000) Human Factors: Guidelines for telecommunications relay services for text and video
  • ISO/CD 24500 Guidelines for all people, including elderly persons and persons with disabilities - Auditory signals on consumer products
  • ISO / IEC 24755 (2007) Information technology - Screen icons and symbols for personal mobile communication devices
  • ITU-T E.161 (2001) Arrangements of digits, letters and symbols on telephones and other devices that can be used for gaining access to a telephone network
  • ITU-T F.790 (2007) Telecommunications accessibility guidelines for older persons and persons with disabilities

Further information

  • Richman, G.D.  & Welsby, K. (1995) BT screenphone services in the UK. proceedings of Telecommunications, 1995. Fifth IEE Conference on Publication Date: 26-29 Mar 1995
  • Schwartz, B. K. & Weinstein, S. B., (1993) Dual-media messaging using screen telephones on the telephonenetwork. Proceedings of IEEE International Conference on Communications. Volume 2, Issue , 23-26 May 1993 Page(s):1183 - 1188 vol.2
  • Wikipedia (2009) iPhone. [accessed 20/04/09].