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Test Consoles, Calibrators and Scale Drawing Machines for Electrical Indicating and Measuring Instruments: Electrical Instruments and Apparatus-Namely, Voltmeters, Potentiometers, Wattmeters, Ammeters, Galvanometers, Magnetic Testing Instruments, Voltage Multipliers, Voltage Dividers, Volt Ratio Boxes, Decade Boxes, and Wheatstone Bridges; Laboratory Standard Electrical Instruments-Namely, Standard Cells, Standard Magnets, Standard Resistors, Standard Shunts, Reference Standard Dynamometers and Moving Iron Instruments; Differential Measuring Instruments for Measuring the Difference Between Two Electrical Values-Namely, Comparators, Ratiometers