| 摘要 |
PURPOSE:To avoid erroneous data from being transmitted by superimposing an AC voltage having two frequencies on a DC voltage of two levels and applying the result to an input terminal to eliminate the effect of noise included in a signal to be modulated. CONSTITUTION:An output of a logical circuit 11 is divided into two; one output is fed directly to a modulation circuit 13 using a VCO circuit and the other output is fed to the modulation circuit 13 via a spare modulation circuit 17. Thus, a DC voltage 12 having two levels corresponding to 1 and 0 of the logical circuit 11 and an AC voltage 18 having two frequencies corresponding to 1 and 0 of the logical circuit 11 are applied to the modulation circuit 13 while being superimposed. The superimposed signal is separated at the reception side of data, restored respectively and collated so as to discriminate a normal signal from a signal caused by noise. |
