Apparatus for testing gas, liquids and solids; Components for electrical mains in the nature of electric wires, connectors, circuit breakers, cables; Computer-controlled apparatus for testing and measuring radio frequency signals, concentrations of gas and liquids, audio signals; Computer stands specially designed for holding a computer, printer and computer peripherals; Drum units for printers, facsimile machines, scanners, copying machines and multifunction electronic devices for use in cop...