In
telecommunication, a
maritime broadcast communications net is a
communications net[?] that is used for international distress calling, including international lifeboat, lifecraft, and survival-craft
high-frequency (HF); aeronautical emergency
very high-frequency[?] (VHF); survival
ultra high-frequency[?] (UHF); international calling and safety very high-frequency (VHF); combined scene-of-search-and-rescue; and other similar and related purposes.
Note: Basic international distress calling is performed at either medium frequency[?] (MF) or at high frequency[?] (HF).
Source: from Federal Standard 1037C