All NEW fixed VHF radios are now required to include Digital Selective Calling (DSC) capability. If your DSC-equipped radio is interfaced with a GPS receiver it will be able to transmit your vessel ID number, your position and, with some higher-end radios, the nature of your distress call (undesignated, fire, flooding, collision, grounding, capsize, sinking, adrift, abandoning, piracy, MOB). In an emergency, one push of a button will make your DSC radio send an automated digital message on VHF Channel 70, which can be received by other DSC radio-equipped vessels and the Coast Guard. The radio will automatically change to Channel 16 for voice communication after this information has been sent, allowing you to communicate by voice with would-be rescuers.
However, it has come to the Coast Guard’s attention that an automatic channel switching feature found on certain models of Digital Selective Calling (DSC) equipped VHF marine radios may create an unintended hazard by automatically switching from a working channel that might be in use at the time to Channel 16 when the VHF marine radio receives a DSC distress alert, distress alert acknowledgment or other DSC call where a VHF channel number has been designated. This could happen without a vessel/radio operator’s immediate knowledge and could initiate an unsafe condition by which the vessel/radio operators would believe they were communicating on a working channel such as Channel 13 when, in fact, they were actually on Channel 16.
Imagine a towboat operator on the lower Mississippi River making passing agreements on VHF channel 67 and then suddenly, without warning, not being able to quickly reestablish communications with those vessels because his/her radio automatically switched to Channel 16 instead.
Since this unsafe condition can happen at any time, the Coast Guard strongly recommends disabling the automatic channel switching feature when maintaining a listening watch or communicating on the designated bridge-to-bridge radiotelephone, or while monitoring the vessel traffic services (VTS) channel. Radios that lack the disabling feature should not be used for bridge-to-bridge or VTS communications.
Below is the actual alert issued by the USCG.
*** Special Notice Regarding U.S. Coast Guard MARINE SAFETY ALERT
AUTOMATIC CHANNEL SWITCHING ON DSC-EQUIPPED RADIOS. ***
Certain models of Digital Selective Calling (DSC) equipped VHF maritime radios will automatically switch from a working channel to Channel 16 upon receipt of a DSC distress alert, distress alert acknowledgment and other DSC calls in which a channel number has been designated. A navigation safety hazard may consequently occur if the radio is being used to maintain a listening watch or to communicate on the designated bridge-to-bridge radiotelephone or vessel traffic services (VTS) monitoring channel. You may view updated information including a listing of manufacturers of radios believed to be affected by this Safety Alert by clicking this link.