Audio visual equipment, namely, computer interfaces, video and audio distribution amplifiers, video and audio switchers, video and audio matrix switchers, transmitters and receivers for sending video, audio, and control signals over unshielded twisted pair cables, video and audio test signal generators, audio amplifiers, audio summing amplifiers, microphone to line level preamplifiers, microphone mixers, volume and tone controllers, digital visual interface or DVI transmitters and receivers, ...