Here is what FCC said about the IP address of each device...
New Ten-Digit Numbering and Emergency Call Handling Procedures for Internet-Based Telecommunications Relay Services
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receive a call from a voice telephone user when the caller dials the VRS or IP Relay user’s ten-digit telephone number. (The caller does not need to know the VRS or IP Relay user’s IP address to make the call.)
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Read what they explained, still IP address exists no matter what.
DHB