In the article the problem of fuzzy binary logic modeling for digital devices (DD) is investigated. In contrast to the similar classic problem of logical simulation, it is assumed that inputs signals of DD are fuzzy signals. In the real of DD for each input (0 or 1) there is a certain voltage range. If an input signal is out of the range, the correct signal identification is not guaranteed. The fuzziness of input signals means that there observed values can be either within of the defined range, or out of it.