71 FAA Chart Users’ Guide - IFR Enroute Symbology NAVIGATION AND COMMUNICATION BOXES - COMMON ELEMENTS RADIO AIDS TO NAVIGATION (Continued) ILS Localizer Example with Back Course (Chart: Enroute Low L-1 US) LOW ALTITUDE ILS LOCALIZER HIGH ALTITUDE - ALASKA VOR/DME RNAV WAYPOINT DATA Frequency Identifier Reference Facility Elevation Radial/Distance (Facility to Waypoint) ILS Localizer Back Course with additional navigation function ILS Localizer Course with additional navigation function LOW ENROUTE CHARTS RCO Frequencies  NAVAID Name FREQ, Ident, CH, Morse Code Latitude, Longitude Controlling FSS Name COMMON ELEMENTS (HIGH AND LOW CHARTS) RCO Frequency  Single Frequency Multiple Frequencies  Frequencies transmit and receive except those followed by R  and T: R - Receive Only T - Transmit Only NAVAID Box Thin line NAVAID boxes without frequency(s) and FSS radio name  indicates no FSS frequencies available. Shadow NAVAID box indicates NAVAID and Flight Service Station  (FSS) have same name. HIGH ENROUTE CHARTS RCO Frequencies  NAVAID Name Frequency, Ident, Channel, Latitude, Longitude Controlling FSS Name VHF/UHF LF/MF