Samsung Galaxy S II Online User's Manual page 57

WARNING: 911 Emergency Calling
Boost Mobile 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 software used by PSAPs. This matter
has been brought to the attention of the FCC,
and the wireless industry and the PSAP
community are currently working to resolve this.
2B. Making and Answering Calls 42