Metering equipment symbols
                                        The following IEC 60417 and ISO 7000 symbols may be used on the metering equipment:
                                        
                                            
                                            
                                            
                                            
                                                
                                            
                                            
                                                
                                                    
                                                         
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                                                    IEC 60417-5017 | 
                                                    
                                                         Earth; ground
                                                         
                                                        To identify an earth (ground) terminal in cases where neither the symbol 5018 nor 5019 is explicitly required. 
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                                                    IEC 60417-5018 | 
                                                    
                                                         Functional earthing; functional grounding (US) *
                                                         
                                                        
To identify a functional earthing (grounding) terminal, for example, of a specially designed earthing (grounding) system to avoid causing malfunction of the equipment. 
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                                                    IEC 60417-5019 | 
                                                    
                                                         Protective class I; Protective earth/ground
                                                         
                                                        
To identify any terminal which is intended for connection to an external conductor for protection against electric shock in case of a fault, or the terminal of a protective earth (ground) electrode. 
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                                                    IEC 60417-5172 | 
                                                    
                                                         Protective class II equipment **
                                                         
                                                        To identify equipment meeting the safety requirements specified for Class II equipment (double or reinforced insulation). 
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                                                    ISO 7000-0434B | 
                                                    
                                                         Caution, refer to accompanying documents
                                                         
                                                        
To indicate that caution is necessary when operating the device or control close to where the symbol is placed. To indicate that the current situation needs operator awareness or operator action in order to avoid undesirable consequences. 
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                                                    ISO 7000-1641 | 
                                                    
                                                         Operator's manual; operating instructions
                                                         
                                                        To identify the location where the operator's manual is stored or to identify information that relates to the operating instructions. To indicate operating instructions should be considered when operating the device or operating controls close to where the symbol is placed. 
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                                        * There may be national differences concerning the use of this symbol. 
                                        **  Protective class equipment requirements are outlined in IEC 61140.