indicate a period when a speech continues further the output of the comparator 10 is kept at a level 34 0 34 for a period when the output s 39 v of the integrator 4 is less than the output of the selector 6 to indicate a period when the speech pauses the output of the comparator 10 is applied to a coder 11 in the period when the output of the comparator 10 takes the level 34 1 34 that is the period when the speech continues the coder 11 extracts transmission parameters such as a pulse indicative of a fundamental waveform pattern and the pitch period of the pulse from a residual signal which is delivered from the speech analyzer 2 to produce a voiced frame in the period when the output of the comparator 10 takes the level 34 0 34 the coder 11 produces an unvoiced frame the voiced and unvoiced frames thus obtained are successively delivered from a coded data output terminal 12 the speech analyzer 2 and the coder 11 mayb e the same ones as used in the conventional systems which are described in the above referred articles each of the frames delivered from the coder 11 contains a flag for discriminating between voiced and unvoiced.