Oceanic ATOM 3.1 Wristwatch Dive Computer, Transmitter, USB Powered by Oceanic's Exclusive Dual Algorithm allowing you to choose the decompression algorithm basis that best suits your diving needs without compromising safety Wireless Air Integrated Technology allows streamlined and accurate monitoring of tank pressure 4 Operating Modes: WATCH (Alternate Time (with option to display Main and Alternate simultaneously), Chrono, Daily Alarm, Countdown Timer), NORM (Air and Nitrox), GAUGE (with run timer) and FREE (tracks calculations to allow switching between NORM and Free) Switch between 3 independent transmitters, with up to 3 nitrox mixes to 100% O2 Improved user-interface with "Step Back" History - allows forward and backward navigation through menus and setting