| 摘要 |
PURPOSE:To minimize the noise due to an error in a transmission line by sending a differential PCM data generated by differential operation between PCM data strings while adding a maximum data at every data group period. CONSTITUTION:The differential operation device 23 of a modulation side 11 obtains a differential PCM data 26a being each difference data from a PCM data 16 obtained by applying A/D conversion 16 to an analog signal 15. On the other hand, the PCM data 16a is grouped and a maximum data representing the maximum amplitude of a consecutive signal in the group is detected and hled by a maximum value detection means 12. The data from the maximum value detection means 12 is added (28) to a difference PCM data 26a and the result is sent (29). When the decoded recovery PCM data has a larger absolute value than the received maximum data, the demodulator side 13 applies amplitude limit 14 to the recovered PCM data within the maximum data.
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