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measuring and testing equipments; namely, oscilloscopes, signal generators, digital frequency counters, automatic distortion sensing meters, digital multi-meters, wow and flutter meters, ICR (Inductance, Capacitance, Resistance) meters, puncture/insulation testers, instrument test leads and probes, logic probes, logic pulsers, power supplies, voltage regulators; public address systems comprising amplifiers, speakers, speaker horns, speaker horn driver units, microphones, microphone stands, matching transformers and speaker volume attenuators, and rack mounted public address systems comprising cabinet racks, cases, and blank panels, pre-amplifier units, power amplifier units, monitors, speaker selectors, input panels, emergency alarm units, electro-chime units, cassette player units, AM/FM tuner units, recorder players, power switching panels, timing programmers, emergency battery units, air blower units; closed circuit television camera monitoring systems comprising video cameras, video sensors, video monitors, video timers and video automatic switchers, video amplifiers, video distributors, panning unit controllers and panning units, video camera housings, and video camera mounting brackets; audio/video intercom apparatus for use in providing video and audio surveillance as well as to control the entry of individuals at a remote entrance