The network performance objective for the psophometric e.m.f. of the noise produced by magnetic and/or electrostatic induction from all the power lines affecting one or more parts of a chain of telephone lines’) joining a subscriber’s set to its international centre should not exceed 1 millivolt, this being the value at the linel) terminais of the subscriber’s set (when receiving), it being assumed that the telecommunication installations inserted in that chain are balanced to earth as perfectly as possible, in conformity with the most modern equipment construction.
ITU-T G.123-1988 Referenced Document
ITU-T G.123 Circuit Noise in National Networks - General Characteristics of International Telephone Connections and Circuits (Study Groups XII and XV) 6 pp*， 1989-01-01 Update