Telecommunications Relay Service 
Telecommunications Relay Service (TRS) is a telephone service that allows persons with hearing or speech disabilities to place and receive telephone calls. There are several forms of TRS, depending on the particular needs of the user and the equipment available. For an explanation of each of the different types of services listed below please go to the FCC website.
For a list of companies that provide access to each type of relay service please click on the appropriate link below.
Text-to-Voice TTY-based TRS (“Traditional” / 7-1-1 / Tennessee Relay Service)
(Includes Voice Carry Over, Hearing Carry Over Services, and Speech-to-Speech (STS) Relay Services)
Sprint National Traditional Relay Services
Speech-to-Speech (STS) Relay Services:
Sprint Relay
Shared Non-English Language Relay Services
CSDVRS Video Relay Service
Global VRS
Hamilton Relay Captioned Telephone Relay Service
Purple Communications Video Relay Service
Sorenson Communications Video Relay Service
Sprint Spanish Relay Service
Captioned Telephone Service
ClearCaptions
Hamilton Relay Captioned Telephone Relay Service
Sorenson CaptionCall Captioned Telephone
Sprint Captioned Telephone
Video Relay Service (VRS)
Convo Communications Video Relay Service
Global VRS
LifeLinks Video Relay Service
Purple Communications Video Relay Service
Sorenson Communications Video Relay Service
ZVRS Video Relay Service
Internet Protocol (IP) Relay Service
Sprint IP Relay Service
IM Relay Services
Sprint IP Using Instant Messenger
Federal Relay
https://www.fcc.gov/consumers/guides/telecommunications-relay-service-trs
Conference Captioning
Sprint Relay Conference Captioning
Miscellaneous Article
Information about Telecommunications and Computer Accessibility