Adding a definition for RTT reference terminal
In Annex C, the tests for clause 6.2 refer to an RTT reference terminal. An RTT terminals can only be considered as a suitable reference terminal if it fully and accurately conforms to the technical solution adopted by a specific RTT service provider. Given the diverse technical solutions adopted by European RTT service providers, it is no surprise that currently no RTT reference terminals have been identified.
Although no European RTT reference terminals exist, it is easy to define what they are. So, it is proposed that the following definition be added to the next version of EN 301 549:
RTT reference terminal: a terminal that meets all the operational and accessibility standards that apply to a specified communications environment
NOTE 1: The design of, or choice of, RTT reference terminal would be by agreement amongst those with the responsibility for ensuring that ICT will interwork within a specified communications environment.
NOTE 2: When the specified communications environment does not have a specified terminal interface, the reference terminal can be considered to include its operational system environment.
If RTT reference terminals are recognised for different RTT deployment technologies, it might be beneficial to have them identified in future versions of EN 301 549. However, as technologies evolve the recommended RTT reference terminals may also need to be revised. A reference within the EN to a register of "approved" RTT reference terminals may be a better way to identify the currently recommended reference terminals in a standard that is likely to evolve much more slowly than the development of RTT technology platforms.