Sonar Tab ............................................................................... 70Alarms Tab ............................................................................. 71Calendar Tab .......................................................................... 73Celestial Tab .......................................................................... 74Message Tab .......................................................................... 78Display Tab ............................................................................ 79Sound Tab .............................................................................. 80Setup Tab ............................................................................... 80Setting Up and Using Sonar .............................................89Showing Sonar on the Map Page ......................................... 89Using the Sonar Page ........................................................... 90Setting Up Sonar ................................................................... 93Understanding Sonar ............................................................ 97Appendix ..........................................................................101Specifications ...................................................................... 101Optional Accessories .......................................................... 102Installation Information ....................................................... 103Learning About GPS ........................................................... 107LORAN TD Setup ................................................................. 109Map Datums and Location Formats ...................................111Digital Selective Calling (DSC) ........................................... 112Messages ............................................................................. 114Data Field Options ............................................................... 116Software License Agreement ............................................. 118Product Registration ........................................................... 118Limited Warranty ................................................................. 119FCC Compliance .................................................................. 120Index .................................................................................121GPSMAP 276C Owner’s Manual iiiINTRODUCTION > TABLE OF CONTENTS