26 PANEL INSTRUMENTS FOR DISPLAYING CONTROL AND/OR READ-OUT SIGNALS, WITH OR WITHOUT RECORDING FACILITIES, WHICH ARE ELECTRICALLY OPERATED, FOR PURPOSES SUCH AS CHECKING OR CONTROLLING TEMPERATURES, GAS OR FLUID MIXTURES, MEASUREMENT OF ELECTRICAL ENERGY, AND OTHER VARIABLES NEEDED TO BE OBSERVED OR CONTROLLED IN INDUSTRIAL OPERATIONS; AND PARTS AND FITTINGS FOR THE AFORESAID