Power ON/OFF connects the MF/HF radio to its power supply, so unless or until it is switched on, the radio is useless. For some equipment there is a dedicated push button control, but for more portable equipment it is combined with the volume control.

Volume makes the level of sound higher or lower from the loudspeaker.

Practise on a MF/HF radio simulator

The MF/HF is turned on by a single press on the ON/OFF/Volume button. The MF/HF is turned off by pressing the ON/OFF/Volume button for 4 seconds. This is always indicated by a countdown window in the information display, except if the radio is powered-down in distress mode. Any connected devices (Alarm Panel, Handset, Control Units) will be operational only if the MF/HF is powered. The start-up display is the last used mode.
Note: The equipment should always be switched on while at sea in order to maintain continuous DSC watch.

The volume of the loudspeaker (internal and external) is adjusted by turning the VOLUME control. The volume level is visualized in the display. To increase the volume, turn the knob further clockwise. The volume can be adjusted to mute mode by turning the volume control left.