Gives standard conditions of measurement and methods of measuring the characteristics common to sub-systems of terrestrial line-of-sight radio-relay systems and to simulated radio-relay systems using frequency modulation. The tests described are limited to analogue transmission systems. Standardizes the conditions and methods of measurement to be used to ascertain the performance of terrestrial radio-relay systems and of the equipment used in such systems, and facilitates the comparison of the results of measurements made by different observers. Contains details of selected methods of making measurements to enable the assessment of the essential properties of a terrestrial radio-relay system and of the equipment used in such systems.