This part of IEC 61606 is applicable to the basic measurement methods of audio equipment for professional use. The definitions, measuring conditions and methods common to both consumer and professional equipment are described in the IEC 61606-1. This standard contains details of definitions and measuring conditions and methods applicable to professional equipment which differ from those described in IEC 61606-1. This standard excludes consideration of – measurement of low-quality audio devices, – measurement of low-bit-rate audio devices (‘sub-band’ or ‘perceptual’ coding devices), – measurement of devices which significantly modify time or frequency characteristics of the signal, such as pitch shifters or reverberators, – measurement of signals from analogue input to analogue output, beyond the most general, – EMC and safety related testing