used : many user profiles have to be taken into account. Such methodology is named Universal Design. Implementation of the standard Available implementations A number of European companies including 4CTel, Aupix, IVèS, nWise, Omnitor, and Orange Labs produced implementations. These are mostly used to provide user-to-user calls and relay services for deaf and hard of hearing people. REACH112 Total conversation was piloted in a European project called REACH112, named after the 1-1-2 European emergency number, whose purpose was to carry out test deployment of total conversation in a live environment with several thousands users and for three usages: European wide person to person calls Total Conversation Relay Services for deaf people Total Conversation used for emergency calls. Specifications Total conversation specifications describe: An interconnection interface between total conversation service providers including relay services. A user to network interface for videophone manufacturers. A call interface for Next Generation Emergency Services in Europe Europe including an information sharing capability. Total conversation defines three basic services seamless multimedia person to person calls including the ability to call regular telephone users. the ability to invoke a relay service by deaf or hard of hearing persons, the ability to call emergency services in total conversation mode. Example of technical protocols used by total conversation are: Session Initiation Protocol for call signalling, T.140 with an RFC 4103. for real-time text (RTT) Video codecs H.263 and preferably H.264. Audio codec ITU-T G.711 and other as commonly used in VoIP calls. (* Use of Common Alerting Protocol may be also considered to share information with Emergency Services.) Over instant messaging AOL Instant Messenger supports the simultaneous use of audio, video, and real-time text via the "Real-Time IM" feature. This would be considered compliant with Total Conversation. For other chat networks such as Google Talk, the XMPP protocol technically allow for total conversation by combining multiple XMPP Extensions, such as XEP-0266 audio, XEP-0299 video, and XEP-0301 real-time text. As of December 2011, Google Talk only supports audio/video, but not real-time text yet. Skype has been supporting simultaneous audio, video, and real-time text. IP multimedia subsystem Total conversation basically provides a multi-media call services with specific media enabled. The currently most common implementation environment is native SIP as described above. Total conversation can also be implemented in other call control environments. One such environment is IP Multimedia Subsystem (IMS) in its IMS multimedia telephony service. Firstly, total conversation can be