Electrical and electronic apparatus, instruments and devices, namely, amplifiers, distributors for electrical signals comprising video, audio, data, test, control, television and telephony signals, distribution amplifiers for video, audio or communications signals, balun transformers, cable connectors, circuit boards, re-clockers for removing noise and jitter in serial digital signals, automatic gain control devices for automatically adjusting video, audio or communications signal levels, equalizers for video, audio or communications equipment, filters for frequency compensation of signal transmission lines, hum buckers and hum cancellation devices for removing noise from signal transmission lines, [ computer programs for use in television and/or video production and editing, ] computer programs for performing electronic system diagnostics, network management software for controlling the distribution of electrical signals comprising video, audio, data, test, control, television or telephony signals, or combinations thereof; [ data storage devices, namely, optical disks, magnetic disks, read-only memory and random access memory, all having stored thereon computer programs for use in television or video production and editing, for performing electronic system diagnostics or for controlling the distribution of electrical signals comprising video, audio, data, test, control, television or telephony signals, or combinations thereof; ] electrical cables, electrical controls for video, audio or communications automation and electrical control panels, interface panels for video, audio or communications systems, electrical signal converters and translators for format conversion of video, audio or communications signals, including electrical to optical conversion; analog to digital converters, digital to analog converters, electrical signal delay modules, electrical signal encoders and decoders, electrical signal generators, electrical signal interface units, electrical signal mixers, electrical signal modulators and demodulators, electrical signal routers, electrical signal switchers and switching matrices for video, audio or communications signals, fiber optic cables and cable connectors, fiber optic transport systems comprising electrical and optical communications instruments and components in the nature of optical transmitters and optical receivers; fiber optic modems, fiber optic signal transmitters, fiber optic signal receivers, fiber optic switches, fiber optic routers for high-speed transport for video, audio or communications, machine controllers in the nature of electronic control systems for machines, optical signal multiplexers, optical signal receivers, optical signal repeaters, optical signal transmitters, media converters, ethernet fiber optic media converters, media converters for component video or graphics, computer networking hardware, video networking devices, namely, hubs, switches and routers; optical networking devices, namely, hubs, switches and routers; oscillators, power supplies, video signal keyers, loss detectors, sound level meters, signal clampers, and video signal processors and structural parts therefor sold as a unit