Hitachi SH-G1000 - Manual (Page 96)

Section 2: Understanding Your Device
88 2C: Controlling the Phone Function’s Settings
5. “TTY is available” appears.
Note: You cannot change the TTY setting during a call.
IMPORTANT NOTICE: 911 Emergency Calling
Sprint recommends that TTY users make emergency calls by other
means including Telecommunications Relay Services (TRS), analog
cellular, and landline communications. Wireless TTY calls to 911 may be
corrupted when received by public safety answering points (PSAPs)
rendering some communications unintelligible. The problem
encountered appears related to TTY equipment or software used by
PSAPs. This matter has been brought to the attention of the FCC, and the
wireless industry and PSAP community are currently working to resolve
this.