The objective is that the following values should not be exceeded: difference between the mean value and the nominal value of the overall transmission loss: 0.5 dB for all circuits, standard deviation about the mean value of the variation of the overall transmission loss: 1.0 dB for all circuits. However, in the case of circuits which are set up, wholly or in part, on older type equipment, and which are composed of two or more circuit sections, a standard deviation not exceeding 1.5 dB may be admitted.
ITU-T M.160 FRENCH-1988 Referenced Document
ITU-T G.214 LINE STABILITY OF CABLE SYSTEMS*， 1993-01-01 Update
ITU-T G.231 ARRANGEMENT OF CARRIER EQUIPMENT*， 1993-01-01 Update