Electric, electronic and optical measuring, signalling, checking apparatus and instruments specifically, electric apparatus and instruments for electro-acoustics, namely, speakers, equalizers, audio synthesizers, audio transmitters, high-frequency audio receivers, high-frequency input modules for providing a harmonious sound balance, parts for the aforesaid goods; active interfering noise suppression devices, for use with other audio and audio visual systems; analog and digital electro-acoustic systems and apparatus, namely, electro-acoustic systems comprised of digital sound filters, computers, analog-to-digital sound converters, pocket audio transmitters and pocket audio receivers for the UHF and VHF ranges, and parts thereof, diversity audio receivers, small audio receivers, live news coverage apparatus, namely, broadband audio transmitters with command audio receivers, backward channel audio transmitters, diversity program audio receivers, command audio transmitters, for recording, transmitting and reproducing audio signals; audio filters, audio amplifiers, electrical volume controls, loudspeakers, headsets, microphones, namely, microphones with integrated transmitters, namely, condenser microphones with built-in high frequency transmitters, soloist microphones, pressure microphones, switchable microphones, interface microphones, electret microphones, headset microphones, gooseneck microphones, directional tube microphones, wireless microphones, clip-on microphones; microphone parts, namely, microphone diaphragma capsules, omni-directional electret microphone capsules, omni-directional foil eletret capsules, microphone modules effected through computer aided acoustic design and laser interferometry techniques, microphone terminal distributors, microphone sleeves; aerials, accumulator plugs, plug battery chargers, listener cables, transducers and parts therefor; apparatus for the wireless transmission, transfer and reception of sound or video signals, namely, multi-channel transmitters and single-channel transmitters and signals, namely, multi-channel transmitters and single-channel transmitters and infrared transmitters and receivers [ ; electric, electronic and electro-acoustic apparatus and instruments for communications technology, namely, telephones, hearing and speech attachments augmenters, and pre-recorded floppy discs, tapes and discs featuring operating system software ]