This part of IEC 60268, is applicable to headphones, headsets, earphones and earsets, intended to be used on, or in, the human ear. It also applies to equipment, such as pre-amplifiers, passive networks and power supplies which form an integral part of the headphone system. It does not deal with: a) safety, for which reference should be made to IEC 60065 or another appropriate standard; b) the characteristics of microphones of headsets, for which reference should be made to IEC 60268-4; c) earphones and other devices for hearing aids, for which reference should be made to IEC 60118-0; d) headphones for audiometry; e) headphones and other devices which form part of an active ear-defender system, although some of its provisions may be applicable. This standard specifies the characteristics which should be included by the manufacturer in specifications, and relevant methods of measurement. It includes a classification of the different types of earphone, mainly characterized by the way in which the transducer is coupled acoustically to the ear, and a classification code which may also be used for marking.