| 摘要 |
PURPOSE:To prevent mis-detection, by corresponding a digital signal consisting of a plurality of ''1''s and ''0''s to two frequencies in which the frequency ratio is 1:n(where; 0.5<n<1). CONSTITUTION:In the conventional modulation method, ''0'' signal is made double frequency of ''1'' signal, and ''0'' is constituted with one wave and ''1'' is with a half wave or one wave (A, B in figure), but mis-detection is apt to be caused at demodulation by such modulation system. In this invention, a signal consisting of a plurality of ''1''s and ''0''s bits is corresponded to two frequencies where the ratio of frequency is 1:n(0.5<n<1), the frequencies are related to ''1'' and ''0''s bits, and modulation is made by taking one wave length of the signals as one bit. For example, in case of Fig. C, ''0'' corresponds to 3.33kHz and ''1'' to 3.0kHz, and in case of D, ''0'' corresponds to 2.0kHz and ''1'' to 2.14kHz. Thus, since the frequency of ''0'' and ''1'' is closed, the output ratio when this is recorded and reproduced closes to 1, and stable recording and reproduction is made over a wide range. |
