Where ICT with RTT functionality interoperates with other ICT with RTT functionality (as required by 220.127.116.11) they shall support at least one of the four RTT interoperability mechanisms described below:
a) ICT interoperating over the Public Switched Telephone Network (PSTN), with other ICT that directly connects to the PSTN as described in Recommendation ITU-T V.18 [i.23] or any of its annexes for text telephony signals at the PSTN interface;
b) ICT interoperating with other ICT using VOIP with Session Initiation Protocol (SIP) and using real-time text that conforms to RFC 4103 [i.13];
c) ICT interoperating with other ICT using RTT that conforms with the IP Multimedia Sub-System (IMS) set of protocols specified in TS 126 114 [i.10], TS 122 173 [i.11] and TS 134 229 [i.12];
d) ICT interoperating with other ICT using a relevant and applicable common specification for RTT exchange that is published and available. This common specification shall include a method for indicating loss or corruption of characters.
|Type of compliance||Test
|Result||Pass: Check 1 or 2 or 3 or both 4 and 5 are true
Fail: All of Checks 1, 2, 3 and at least one of 4 or 5 are false