Unless the dive mode turned off, the dive mode activates automatically when you dive deeper than 1.2 m (4 ft). However, you should switch to dive mode before diving to check altitude and personal settings, battery condition and so on.
Each time your Suunto DX enters dive mode, a series of automatic checks are performed. All graphical display elements are turned ON, and the backlight and the beep are activated. After this, your altitude and personal settings are displayed along with the maximum operating depth (MOD), gas content, and PO2 values. Then the battery level is checked.
Between consecutive dives, the automatic checks also show current tissue saturation.
Before leaving on a dive trip, it is highly recommended that you switch to dive mode to make sure everything is functioning properly.
After the automatic checks, Suunto DX enters surface mode. At this point, you should perform your manual checks before entering the water.
If the optional wireless tank pressure transmitter is used, check that:
Temperature or internal oxidation can affect the battery voltage. If you store your Suunto DX for a long period or use it in cold temperatures, the low battery warning may appear even though the battery has enough capacity.
In these cases, re-enter dive mode and check the battery power. If the battery is low, the Low Battery warning comes on.
If the low battery icon appears in surface mode, or if the display looks faded, the battery may be too low. Battery replacement is recommended.
For safety reasons, the backlight and buzzer (sound) cannot be activated when the low battery warning is displayed.