Public address speaker systems; parts and fittings for audio apparatus; panels for the distribution of electricity; power distributors [electrical]; software to control and improve audio equipment sound quality; signal processors for audio speakers; loudspeaker systems; loudspeaker units; cabinets for loudspeakers; loudspeakers; information technology and audio-visual, multimedia and photographic devices; equalizers [audio apparatus]; electronic units for transmitting audio signals; audio electronic apparatus; wireless audio and video receivers; digital audio servers; digital audio players; amplifiers; public address systems; audio amplifiers; audio transmitter units; audio interfaces; audio apparatus; audio frequency apparatus; audio circuit boards; audio mixers