This part of IEC 61603 gives methods for measuring and specifying those characteristics of wide band audio IR transmission systems not covered by part 1 of this standard (see also 3.1). It allows systems which make different economic use of the available bandwidth to be described in order that conclusions regarding interference and compatibility can be drawn. Interface (matching) values and other system characteristics are also covered. This part of IEC 61603 replaces chapter 1 of IEC 60764, which covers only two carrier frequencies for analogue audio signals, and which does not cover digital audio.