The CCITT, considering that, for a precise definition of the degree of distortion in service permitting the comparison of results of measurements obtained under similar conditions in different places, it is advisable to standardize the wording of the text that should be transmitted for the test; that it is best to choose a text that can be received directly by start-stop equipment and that also presents a sequence of the combinations recognized as those that generally cause the maximum distortion.
ITU-T R.51 FRENCH-1988 history
1988ITU-T R.51 FRENCH-1988 STANDARDIZED TEXT FOR DISTORTION TESTING OF THE CODE - INDEPENDENT ELEMENTS OF A COMPLETE CIRCUIT