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 two data packets. The first data packet includes a
segment of time having a starting boundary that is synchronized with the
start of the encoded tone and extending for a time period equal to about
one-half the total time period of the tone. The second packet encodes the
remaining half of the audible tone. At the receiving end, data packets
encoding a textual character are ordered according to the position
occupied by the data encoded by the packet within the sequence of tones.
If any unpaired packets of data are detected at the receiving end, the
characteristics of the packets that are unpaired are copied into the time
slot that would have been occupied by the missing packet. Accordingly,
the present invention allows for the accurate transmission of textual
characters over VoIP networks, even where a packet of data encoding part
of a sequence of packets encoding a character is dropped.