| 摘要 |
PURPOSE:To secure information transfer and also to reproduce audio signals of good quality by modulating sine-wave signals, differing in frequency ratio and in band, and then by transmitting the modulated signals being superposed on an audio signal. CONSTITUTION:Respective sine-wave signals, differing in frequency ratio and arranged by bands, are modulated 12 according to a change in input information A and then sent out to transmission line 23 being superposed on audio signal A. At a reception side, comb line filters 26 and 37 are formed which extract the pitch frequency of audio signal A at 27 and stop a frequency an integer greater than the pitch frequency. A signal passing through filter 26 is separated 28 and 29 into two components of different frequency bands and on the basis of each band output, analyzers 31 and 32 determine one frequency each greater than a fixed threshold level. Then, the output of analyzer 32 is converted 33 at a frequency ratio between two frequencies to equalize the determined frequencies of both the bands to each other and information A is detected 34 by this frequency to obtain original audio signal E through comb line filter 37. |
