Which channel is used to initiate a Distress alert transmission?

The channel used to initiate a Distress alert transmission is Ch-70 DSC. This channel is specifically designated for Digital Selective Calling (DSC) and is used internationally for sending distress alerts and other safety-related communications. When a vessel is in distress and needs assistance, it sends a DSC distress alert on Ch-70, which automatically relays the information to other vessels and shore stations within range.

Ch-70 is equipped to handle the automated nature of DSC, which allows for a more efficient and precise sending of distress signals compared to traditional voice communication. The use of DSC frees up voice channels for further communication once the distress alert has been sent, allowing for an organized response to emergencies.

In contrast, while Ch-16 is widely known and used for distress calls in radiotelephony, it is primarily intended for voice communications. Ch-6 and Ch-9 serve other purposes within the GMDSS framework and are not designated for initiating distress alerts in the same context as Ch-70. Thus, Ch-70 DSC is the correct channel for initiating a Distress alert transmission.