PURPOSE: To reproduce data by digital processing entirely by detecting a digital data signal rising by a window pulse which corresponds to a rise to a level H.

CONSTITUTION: A window pulse 39 and a synchronous detection signal from a detecting circuit 38 are supplied to an AND circuit 40 to extract the window pulse 39 while the synchronous detection signal is at a high potential. Then, the extracted pulse 39 and an input signal 44 are supplied to a data detecting circuit 41, which detects data 1 when the input signal rises within the range of the window pulse 39 or data 0 when not, thereby obtaining data at an output terminal 42. Since this is performed entirely by digital processing, noise resistance characterstics are improved, the influence of temperature drift, etc., is lessened, and the variance due to temperature characteristics is reduced.