An adaptive coder and decoder for reducing the bit rate required to trans digitally encoded speech signals. The invention relies on the fact that the speech pattern of the average talker contains significant numbers of inter-syllable and inter-word pauses. The coder includes circuitry that monitors the idle pattern code generated by the coder's analog-to-digital converter and a code word generator that generates one or more special code words that are substituted for idle pattern code sequences of predetermined length. The speech signal and special code words are then fed into an elastic buffer and transmitted to the distant receiver at a lower bit rate than was employed for the encoding process. At the receiving location, the decoder recognizes the special code words, substitutes an idle pattern bit stream of the appropriate length for the code words and then reads-out the contents of an elastic input buffer at a higher bit rate than was used to transmit the incoming signal, that is, at the same bit rate as was initially used at the coder.