The conditions of measurement characteristics given in this part restrial radio-relay and satellite modulation. These test methods systems of all capacities and the between the parties concerned. and the methods of measuring the of the standard are common to terearth station systems using digital are general and are applicable to tests to be made should be agreed The object of this standard is to describe the conditions and methods of measurement_ to be used to ascertain the performance of digital microwave radio transmission systems and of the equipment used in such systems, and to facilitate the comparison of the results of measurements made by different observers. It contains details of selected methods of making measurements recommended for assessing the essential properties of a digital microwave radio transmission system and of the equipment used in such systems. These methods are neither mandatory nor limiting; a choice of measurements can be made in each particular case. If necessary, additional measurements may be made but these should preferably be carried out in accordance with the standards laid down by other IEC Technical Committees, or SubCommittees or by other international bodies. Limiting values of the various quantities for acceptable performance are not specified since these should be given in the detailed equipment specification. The methods of measurement described in this standard are intended for "type" and `acceptance" tests under simulated conditions and they may also be used for factory tests.