Abstract: On the basis of the Threshold Decision rule calculations are made of the error probability of detecting phase-modulated binary codes in the system of Pseudo-random code for the measure of distance. The results are compared with results of measurements on the basis of the maximum likehood decision rule. It is pointed out that under similar conditions, results obtained from measurements according to the two rules from the point of view of statistical average differ very little; results obtained from the former differ only by 3dB from the later, even calculations are made according to the longest trapping time.