Radio equipment – Sea areas A1, A2 and A3

These vessels have two options to satisfy their GMDSS requirements. The options allow a vessel to choose from the primary method to be used for ship-shore alerting ;
Every ship engaged on voyages beyond sea areas A1 and A2, but remaining within sea area A3 ( INMARSAT AREA ) shall be provided with the minimum equipment A1 & A2 plus either:

  • An Inmarsat C ship earth station  Primary
  • A second Inmarsat C or HF Radio telex NBDP
  • An MF/HF radio installation and 2187.5 kHz DSC watchkeeping receiver;
  • A 406 MHz EPIRB


  • An MF/HF radio installation capable of transmitting and receiving on all distress and safety frequencies in the (marine) bands between 1,605 kHz and 27,500 kHz: using DSC, radiotelephony; and NBDP As primary
  • An MF/HF DSC watchkeeping receiver capable of maintaining DSC watch on 2,187.5 kHz, 8,414.5 kHz and on at least one of the distress and safety DSC frequencies 4,207.5 kHz, 6,312 kHz, 12,577 kHz or 16,804.5 kHz; at any time, it shall be possible to select any of these DSC distress and safety frequencies
  • A 406 MHz EPIRB

In addition, ships shall be capable of transmitting and receiving general radiocommunications using radiotelephony or direct-printing telegraphy by an MF/HF radio installation operating on working frequencies in the (marine) bands between 1,605 kHz and 27,500 kHz. This requirement is normally fulfilled by the addition of this capability in the MF/HF equipment referred to earlier.