Digital Selective Calling and Rescues

In South Africa it is a requirement that Category A, B, C, D vessels and other vessels operating in Sea area A1 should be fitted with a VHF radio that has the DSC functionality.

Digital selective calling (DSC) uses VHF Channel 70 as a digital-only channel. Since January 2016 all fixed-mount radios sold in South Africa have the DSC capability built in.

The VHF radio must be connected to your GPS, or the radio must have an internal GPS receiver, to get the full capability. If not the operator will have to manually enter a new GPS position every 4 hours.

Your VHF radio must be registered with ICASA and the operator must have a Short Range Cerificate. On registration ICASA will issue a ship station license with a call sign and MMSI number for your vessel. The MMSI number must be entered into the radio to activate the DSC functions.

DSC-capable radios can be used to send various types of messages:

  • Emergency calls the coastal radio stations and other vessels
  • Calls to a specific vessels, requesting a voice response
  • Calls to specific vessels, requesting their position
  • Calls to specific vessels, providing position
  • Calls to groups of vessels.

Emergency calls are of the greatest interest to coastal and offshore boaters. When an MMSI number has been entered into the VHF radio, and if it is connected to an operating GPS, DSC allows you to broadcast an emergency call to all vessels within range and your transmission will be picked up by network of remote coastal radio stations. This distress call communicates your identification and your position in one brief call.

For calls to specific vessels you have to know the MMSI number of that vessel.