The user can select one of two ultra-high frequency (UHF) channels as primary while monitoring the other. Should the selected UHF channel fail, the unit will automatically fall back to the corrections from the International Association of Lighthouse Authorities (IALA) beacon receiver. UHF channels can either be manually set or search all Petrobras channels automatically.
Source: “Software / CDU Support.” Support. C-Nav GNSS, n.d. Web. 5 June 2017.