PURPOSE: To reduce errors by recording information with high density by arranging pieces of binary information, sampled and quantized at optional time or before or after it and at different time, into a time series, by obtaining modulated data by making connections one after another, and by performing demodulation.

CONSTITUTION: Natural binary parallel data are converted into Gray codes in a read-only memory 10 and an FF11 holds the data. A shift register 12 converts 8-bit parallel data into a series and a shift register 17 converts the series. In the read-only memory, the Gray codes are converted into natural binary codes. An analog signal is sampled and quantized successively at optional time and at some intervals to obtain binary information, which is made into a time series and connected one after another to obtain demodulated data, thereby performing demodulation by the opposite procedur. Thus, information is recorded with high density and errors in recording and reproduction are reduced.