Art. 54A Radioreglement 1979, Automatic connection system
54A.1 § 1 1) An automatic connection system (ACS) using digital selective calling in MF and HF bands is designed to ensure reliable access to required radio links for mariners. (WRC-23)
54A.2 2) Automatic connection system (ACS) should be in accordance with the most recent versions of Recommendations ITU-R M.541 and ITU-R M.493. (WRC-23)