Data signal reading device

DETAILED DESCRIPTION Overcoming the above-noted drawbacks, the invention provides a data signal reading device in which, instead of an active H level signal with which noise is more liable to interfere, only an active L level signal, with which noise is less likely to interfere, is subjected to decision to thus read incoming data correctly.
More specifically, according to the invention there is provided a data signal reading device for reading an input signal in which data signal segments representing "1" and "0" are determined separately according to two different durations of one of two different levels, and a predetermined duration of the other level is provided between the data signal segments representing "1" and "0", which, according to the invention, comprises: level decision means for subjecting an input signal to level decision while sampling it with a clock signal having a predetermined period to provide decision outputs; a first counter for counting the number of times of occurrence of the one level in response to the decision outputs; a second counter for counting the number of times of occurrence of the other level in response to the decision outputs; initializing means for initializing the second counter when it is determined that the decision output is of the one level; means for suspending the counting operations of the first and second counters for a period of time slightly longer than the shorter of the two different durations when the content of the second counter reaches a predetermined value; and data decision means for deciding data "1" and "0" in the input signal according to the content of the first counter which is obtained when the second counter reaches the predetermined value.