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Plain Old Telephone System (POTS)

Picture of a man using a telephone.The telephone is one of the main communication tools that people use in their everyday lives.

It gives easy access to the outside world. For many people it is their main link with others. This is particularly so for disabled and elderly people. However, the telephone can be a barrier to communication if it is difficult to use.

Problems encountered by disabled people and the ageing population using telephones

Picture of a telephone handset.Many disabled and elderly people have difficulty using telephones. For example, buttons can be difficult to distinguish and some telephones can be difficult to hold without accidently pressing the keys.

The huge range of telephones in all shapes and sizes that come packed with features can also present problems for even the most able user.

Blind and partially sighted

Visual impairment makes it difficult to read displays and markings, especially in low light conditions. Liquid crystal displays can be very difficult to read and visual prompts (such as on payphones), may be unreadable.

Severe visual impairments give problems in performing any visual task. Even locating the telephone may be a difficult matter. Persons with severe visual impairments often need to get very close to the item they are trying to see.

Blind people are not able to use their vision for dialling on a telephone and rely upon tactile and audible signals.

Hearing impaired

A moderate loss of hearing function causes problems in many acoustic environments. Hearing aids may be used in many situations but often will not be used when telephoning because the signal level from the phone is sufficient, particularly when amplification is available. However, there may be difficulties in hearing the phone ring at any distance from it.

A severe functional hearing loss will require full-time hearing aid use. Additional receive amplification may be helpful when telephoning but the major problem is to obtain optimal coupling to a personal hearing aid. Inductive coupling is often the preferred method but some smaller hearing aids are incapable of supporting this connection.

A person with severe hearing impairment may be able to hear over the telephone, but may have severe difficulties in understanding what is being said.

No useful hearing (in the context of telephone usage) necessitates the use of visual modalities, eg. text telephony. Fax and email are not satisfactory alternatives as they do not allow for real-time conversations.

Physically impaired

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.

Those who rely on wheelchairs, walking frames or walking sticks to get about do not generally require special features on telephones, although cordless or mobile phones can be very useful. Positioning of the telephone and the means of access to it may be critical.

Cognitively impaired

Cognitive impairments are varied, but may be categorised as memory, perception, problem-solving and conceptualising disabilities. Dyslexia can cause significant problems in remembering even short sequences of numbers in the correct order. People with an intellectual impairment can often function well when they are familiar with the terminal and system, but can be easily confused when required to respond quickly.

Speech impaired

Speech difficulties (e.g. weak voice and stammering), will hinder use of the telephone network in speech mode.

People with significant problems with voice communication may opt for text-based communication. In many cases the problem may be linked with deafness.

Ageing population

Some members of the ageing population can often experience a range of difficulties with telephones, such as those stated above: from not hearing the telephone ring; being unable to pick the handset up and the incompatibility with a hearing aid.

Checklist for Plain Old Telephone System (POTS)


Many disabled people would be helped by some extra appropriate features on their telephone. Which feature or combination of features is needed will vary from individual to individual.

Picture of a woman using a telephone.

Possible features include:


  • The visual display should be high contrast
  • A socket to permit the connection of an external display with a standard interface would permit users with special needs to connect their own adaptive technology
  • A synthetic speech alternative to the visual display would help many blind people. A means of adjusting the volume and of repeating the messages will be required
  • A tactile display may be useful for services such as caller line identification for blind people who can read braille
  • Visual displays of text must be legible even under adverse lighting conditions; visual (or tactile) indications of line status are essential. A line by line presentation is often preferable to a single line of scrolling text
  • A large character display is essential for many people with a visual impairment
  • A visual display of the line status is essential on Text Send terminals for deaf people, and is desirable on any terminal for use by those with a severe hearing impairment
  • Terminals which offer a full display of text on a visual display unit should allow adjustment of the size of the characters. The characters must also be of good proportions with clear character shapes. There must also be a strong contrast between the characters and the background. It is also helpful to be able to reverse the text from dark on a light background to light characters on a dark background. The display screen should be capable of positional adjustment to avoid any reflected light
  • Picture of a telephone handset.


  • The handset should be easy to grip with sufficient space between the handset and the telephone base unit so that the handset can be picked up and replaced with ease
  • Handset should be lightweight with the balance of weight between the earpiece and mouthpiece even
  • Plug connection of the handset permits the use of alternatives such as a lightweight headset
  • Consideration should be given to the functional shape and size of the handset
  • It is important that the earpiece is large enough and shaped to cover most of the ear, this will help seal the ear to reduce external noise interference
  • Additional earphone enables a user to listen with both ears. Can also be used by a hearing helper who can repeat the message so that it can be lip read

    Hearing aid

  • Coupling to a hearing aid by inductive coupling, infra-red, direct electrical connection or by matched acoustic transducers
  • Hearing aid compatibility so that there is no mutual interference and with minimal change to the setting of the hearing aid


  • Enlarged keys enable persons with poor dexterity to press the correct key; the spacing between the keys is as important as the size of the keys themselves. A concave shape to the keys will also help fingers to stay in place
  • Guarded or recessed keys can help a person who has difficulty in making precise finger movements
  • Tactile feedback that confirms that a key has been pressed can be very helpful
  • Audible confirmation of a key press is helpful for many visually impaired people
  • Users with impaired hearing may require a displayed indication of the number dialled
  • A means of adjusting the key pressure to activate a key is desirable
  • A keypad in the handset can cause problems for persons with poor manual dexterity or reduced strength
  • A plug-in keyboard enables the user to use a device which is customised to their particular needs
  • Standard key layouts are important for people who are blind or who have difficulty in reading the key legends
  • Tactile key markers help people who are blind or have low vision
  • A text send keyboard is required by deaf users who may be using a relay service
  • The keys should be marked with a large clear typeface
  • Speech-input keying is useful for those with hand tremors or a cognitive impairment
  • Picture of a telephone.


  • Microphone amplification will help persons with quiet voices or with restricted neck and chest movement that makes speaking difficult
  • Receiver amplification enables the user to increase the volume of sound (up to 20 dB) coming through the telephone earpiece
  • Ringer pitch adjustable is useful for those whose hearing loss is significantly frequency dependent
  • Ringer volume adjustable gives the possibility to provide good audibility even in domestic environments where acoustic absorption may be high
  • Sidetone reduction is a facility for improving the signal to noise ratio at the earphone by minimising the effects of ambient noise picked up by the microphone and mixed with the incoming speech
  • Visual ringing signal is essential for people who are deaf. Visual signals incorporated in the terminal are not easily seen and are mainly of use as a reminder of line status. An interface should be provided so that external lights or a vibrating pager can be triggered by the phone

    Other features

  • Coupling to a computer is a faciltity which will allow deaf and deafblind users to use their personal computers as text terminals. Enables use of dial-out software and personal electronic phonebook database. It would also allow people with very severe physical disabilities to access the telephone networks through ordinary terminals and allow severely speech-impaired users to connect their communication aids
  • A dial-out buffer memory enables users who are slow in dialling to avoid being timed-out
  • Hands-free operation is valuable for users with severe upper limb impairments, but it must include the call set-up procedures
  • A non-slip base on a phone not designed for fixed mounting is highly desirable for people with uncoordinated movements

Relevant standards

  • 36 CFR Part 1193 RIN 3014-AA19 (1998) Telecommunications Act accessibility guidelines - Section 255
  • 47 CFR Part 6 Access to telecommunications service, telecommunications equipment and customer premises equipment by persons with disabilities
  • 47 CFR Part 7 Access to voicemail and interactive menu services and equipment by persons with disabilities
  • ACIF C625:2005 Information on accessibility features for telephone equipment
  • ACIF G586:2001 Disability matters: Access to communications technologies for people with disabilities and older Australians
  • ANSI/TIA-968-A (2002) Telecommunications - Telephone terminal equipment - Technical requirements for connection of terminal equipment to the telephone network
  • AS 5061 (2008) interactive voice response systems user interfaces - Speech recognition
  • AS/ACIF S040 (2001) Requirements for customer equipment for use with the Standard Telephone Service - Features for special needs of persons with disabilities
  • AS/NZS 4263 (2003) Interactive voice response systems - User-interface - Dual tone multi frequency (DTMF) signalling
  • AS/NZS 4277 (1995) Text Telecommunications - User interface requirements - For deaf people and people with hearing and speech disabilities
  • Picture of a telephone keypad.

  • ETS 300 640 (1996) Human Factors (HF): Assignment of alphabetical letters to digits on standard telephone keypad arrays
  • ETS 300 679 (1996) Telephony for the hearing impaired: Electrical coupling of telephone sets to hearing aids
  • ETSI ES 201 381 (1998) Human Factors: Telecommunication - Keypads and keyboards - tactile identifiers
  • ETSI ETR 029 (1991) Access to telecommunications for people with special needs: Recommendations for improving and adapting telecommunication terminals and services for people with impairments (Superceded by EG 202 116)
  • ETSI ETR 166 (January 1995) Human Factors (HF); Evaluation of telephones for people with special needs: An evaluation method
  • ETSI ETR 334 (1996) Human Factors (HF); The implications of human ageing for the design of telephone terminals
  • ETSI ETR 345 (1997) Human Factors (HF); Characteristics of telephone keypads and keyboards; Requirements of elderly and disabled people
  • ETSI ETS 300 381 (1994) Telephony for hearing impaired people: Inductive coupling of telephone earphones to hearing aids
  • ETSI ETS 300 488 (1996) Telephony for hearing impaired people: Characteristics of telephone sets that provide additional receiving amplification for the benefit of the hearing impaired
  • Picture of a black cordless telephone.

  • ETSI TCR-TR 023 (1994) Human Factors (HF); Assignments of alphabetic letters to digits on push button dialling keypads (superceded by ETS 300 640)
  • ETSI TR 103 073 (2003) Universal Communications Identifier (UCI): Improving communications for disabled, young and elderly people
  • ITU-T E.121 (2004) Pictograms, symbols and icons to assist users of the telephone and telefax service
  • 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 E.920 (1995) Procedures for designing, evaluating and selecting symbols, pictograms and icons
  • ITU-T F.790 (2007) Telecommunications accessibility guidelines for older persons and persons with disabilities
  • ITU-T P.370 (1996) Coupling hearing aids to telephone sets
  • ITU-T P.79 (2007) Calculation of loudness ratings for telephone sets
  • JIS X 8341-4 (2005) Guidelines for older persons and persons with disabilities - information and communications equipment, software and services - Part 4: Telecommunications equipment
  • TIA-504-A (1998) Telecommunications - Telephone terminal equipment - Magnetic field and acoustic gain requirements for headset telephones intended for use by the hard of hearing

Further information