This part of the standard, which is supplementary to Part 1, IEC 835-1-1, describes methods of measurement applicable to terrestrial radio-relay systems using digital modulation. The object of this part is to provide recommended methods of measurement for assessing the essential properties of terrestrial radiorelay systems as well as the associated sub-systems and it is intended to be used in conjunction with Part 1, IEC 835-1-1. Where measurements common to terrestrial radio-relay and satellite earth station systems are required, reference is made to the appropriate section of Part 1, IEC 835-1-1. In such cases, only those special aspects of the measurement appropriate to terrestrial radiorelay systems are described in the sections of this Part 2. The measurements described in the following sections of this part are neither mandatory nor limiting; a choice of measurements can be made in each particular case, e.g., for bit-rates less than about 34 Mbit/s, the signature as well as some of the more sophisticated measurements may not be of interest. On the other hand more comprehensive measurements (under consideration) may be required for complex modulation methods e.g. 64-QAM. Where parameters or methods of measurement are applicable only to terrestrial radio-relay systems, they are fully described within the appropriate sections of this part.