Methods are given in this section for the measurement of the electrical characteristics of frequency modulators. Furthermore, where possible, only measurements involving the basic modulator are considered, that is excluding the baseband section comprising the pre-emphasis network and the networks associated with sound sub-carrier signals, pilot signals and auxiliary signals. Methods of measurement for frequency demodulators are given in Section Five. Measurements between baseband terminals of modulator/demodulator assemblies are covered by various sections of Part 3 of this publication.