PURPOSE: To easily transmit scramble information even when a voice mode is different by superposing the scramble information of digital data on the common free area of plural transmission formats corresponding to plural voice modes.

CONSTITUTION: Scramble information SDA, SIF of digital data DADO is superposed to the common free area DTUSE of plural transmission formats FMTA, FMTB corresponding to plural voice modes. Accordingly, in a transmission side 2, the scramble information SDA, SIF can be superposed by a common processing means, and also, in a reception side 4, as well, the scramble information SDA, SIF can be obtained by a common processing produce. In such a manner, even when the voice mode is different, the scramble information SDA, SIF can be easily transmitted.