VHF Channel 70 / DSC

Dedicated VHF channel 70 (156.525 MHz) used exclusively for Digital Selective Calling. Vessels use DSC on Ch.70 to alert other vessels and coast stations before voice contact on Ch.16, including distress alerts that auto-include MMSI and last GPS position. ITU Radio Regulations Appendix 18 reserves Ch.70 from voice traffic. SOLAS Ch. IV requires GMDSS-compliant vessels to carry VHF DSC, and the 2008 amendments required automatic distress-alert relay capability on coast stations. False alerts remain a concern; SOLAS-mandated annual radio surveys verify alert procedures.