Improve structure of 6.2.3 Interoperability
Points a-d in 6.2.3 are kind of meant to be applicable to different kinds of technologies, but not really consistently. Currently, there is an overlap between c and d, which is confusing.
To make it clearer, we could combine c and d, like this: "c) ICT interoperating with other ICT using technologies other than a or b, above, using either one of the following: (1) a relevant and applicable common specification for RTT exchange that is published and available for the environments in which they will be operating; this common specification shall include a method for indicating loss or corruption of characters; (2) a standard for RTT that has been introduced for use in any of the above environments, and is supported by all of the other active ICT that support voice and RTT in that environment."
Then, in table A.1, we could introduce the different conditions for each point: Condition for a: “Where web pages with RTT functionality interoperate with other ICT with RTT functionality (as required by clause 6.2.1.1), and where the other ICT is directly connected to the Public Switched Telephone Network (PSTN)”. Condition for b: “Where web pages with RTT functionality interoperate with other ICT with RTT functionality (as required by clause 6.2.1.1), and where the other ICT uses VOIP with Session Initiation Protocol (SIP) and uses RTT that conforms to IETF RFC 4103”. Condition for c: “Where web pages with RTT functionality interoperate with other ICT with RTT functionality (as required by clause 6.2.1.1), and where the other ICT uses technologies other than a or b”.