PURPOSE: To eliminate an impulsive distortion and to improve the sound quality, by detecting an error code which produces an abnormal pulse, then replacing the detected code with its preceding code.

CONSTITUTION: An sound digital code transmitted from a transmitter 2 is supplied to a receiving buffer 11 of a reciever 1 via a transmission line 4 and stored there temporarily. The digital code is changed to a pair of error detectable forms by the buffer 11 and applied successively an error detecting circuit 12 and a gate circuit 13. The circuit 12 checks the bit of the code and controls the circuit 13 when a pair of codes are erroneous to prevent a pair of codes which are supplied to a storage circuit 14 from the buffer 11. Then a pair of codes stored precedently in the circuit 14 are applied to a transmitting circuit 15. The output given from the circuit 15 is converted into an analog sound by a D/A converter 3. This prevents the generation of an impulsive distortion and improves the sound quality.