Dark band seen in muscle which is made of the thick filaments
                                                            
                                                     
                        
                                                
                        
                        
                            The universal IFF Mark III frequency band is designated "A" band by the Navy. (This same band is designated "I" band by the Army.) The Army uses the term "A" band to designate a frequency band used in the Mark II IFF system.
                                                            
                                                     
                        
                                                
                        
                        
                            For the wireless term, see A band.