As reference,
https://en.wikipedia.org/wiki/Telecommunications_device_for_the_deaf
I think going with a generic approach is a good idea. In the United States
we use the term "Relay", but elsewhere it's called "Carry Over" with
different suffixes.
So I think your approach of not including specific terms, or protocols like
TTY or Relay or Carry Over is a great idea. However,
VoiceImpairedSupported is a viable option also (someone that is mute,
rather than deaf)
So perhaps just "CommunicationsImpairedSupported" or
"CommImpariedSupported" or "ImpairmentSupport". whatever works.
+1 for both ImpairmentSupport and TollFree to be added.
Thad
+ThadGuidry <https://www.google.com/+ThadGuidry>