Marine VHF Channel 70

Marine VHF channel 70, 156.525 MHz, is reserved exclusively for digital selective calling, not for voice. A ship sends a DSC distress alert, urgency or safety announcement, or routine call as a short data burst on channel 70; the called station’s DSC controller decodes it, alarms, and the two then move to channel 16 or a working channel for voice. ITU Radio Regulations Appendix 18 designates the channel for DSC only, and SOLAS GMDSS ships keep a continuous automatic DSC watch on it. Channel 70 underpins sea area A1, the VHF coverage zone, where a single button press raises the alarm ashore without an operator having to speak.