The present invention is directed to a system for reliably transmitting characters encoded as audible signals using voice over Internet protocol communication systems. According to an embodiment of the present invention, tones within a sequence of tones encoding a textual character are transmitted using...http://www.google.com/patents/US7379431?utm_source=gb-gplus-sharePatent US7379431 - Error correction method and apparatus for TTY on VoIP transmissions
