A cable for use in carrying electrical signals in the audio frequency range. The cable includes an elongate metallic core which can be positioned at the center of the cable. In the case of the coaxial cable, a sleeve of a dielectric material is positioned about the core and a metallic shield is located...http://www.google.es/patents/US4920233?utm_source=gb-gplus-sharePatente US4920233 - Audio cable
