| 摘要 |
PURPOSE:To attain clear discrimination of input signal interruption by providing a threshold value having respectively a prescribed width to the 0 and 1 side of a signal waveform after equalization and discriminating it as input signal interruption when the count of signal number entering the width is a prescribed value or below. CONSTITUTION:Voltages a-d shown in a figure are given respectively as reference voltages of comparators 15-18, the comparators 15, 17 output a pulse when a signal below the reference voltages (a, c) are inputted and the comparators 16, 18 output a pulse when voltages being reference voltages (b, d) or over are inputted, the outputs of the comparators are inputted to AND circuits 19, 20 to constitute window comparators 9, 10. A count circuit 21 counts clock numbers and since this value is inputted to a signal interruption discriminating section 14, which compares the count from the count circuit 21 with the count from a count circuit 13, and when the count from the count circuit 13 reaches a prescribed value or below within a predetermined time, it is discriminated as an input signal interruption. Thus, the signal interruption is discriminated clearly without being affected by other circuits. |
