36This clause introduces the problem space and the current status of assistive technology and communication device technology.
37Abilities and disabilities are explained in the guideline document EG 202 116 on "Human Factors guidelines for ICT products and services; Design for All" . The guideline document describes the characteristics of a wide range of users with disabilities and provides details of their impairments and the resulting disabilities related to ICT products and services. In the context of the present document, the following broad classes of abilities are highlighted, and when impaired, they affect the use of mobile technologies:
language abilities such as speaking, reading, literacy and comprehension.
38These abilities are also described in the document CEN/CENELEC Guide 6  and in the ITU-T FSTP Telecommunications Accessibility Checklist , which provide guidelines for standards developers to address the needs of older people and people with disabilities. The range of disabilities put requirements on services and devices. Some of those requirements can be met by following the "Design for All" guidelines . However, some users, often with multiple disabilities need additional assistance in the form of adaptations to conventional devices. It is therefore important to collect requirements in this area and the present document builds therefore on the results provided in the technical report on "Requirements for assistive technology devices in ICT" . The ITU-T F.790  document provides Telecommunications accessibility guidelines for older persons and persons with disabilities. Therefore, the present document provides recommendations based on requirements listed in existing documents and a gap analysis where existing AT commands have been reviewed (see clause 7). Clause 8 presents suggested solutions related to the development of communication devices in order to facilitate the development and use of external devices. Clause 9 presents specific recommendations and the need for AT commands to support those recommendations.
41Some users with disabilities cannot use communication technologies, even those designed using "design-for-all" principles [3, 25]. In some cases, the requirements for different disabilities conflict with the requirements for other disabilities. Therefore, what is required for those users is a standard solution for adaptation.
426.2.2 Classification of external devices
43Current assistive technology is classified in the international standard ISO 9999 . Although it covers a vast number of devices ranging from abacuses and abdominal hernia aids to zip pullers and zippers, only a few of the devices listed in that standard have the potential to be interconnected to ICT services and devices. The technical report TR 102 068 on "Human Factors (HF); Requirements for assistive technology devices in ICT"  has therefore listed those external devices which can be interconnected to ICT systems, see table 1, together with their codes according to the ISO 9999  classification system.
44Table 1: Relevant external devices in ISO 9999 , listed in