The Iridium Certus plan you choose depends on the terminal you select. There are Land Certus 100, Land Certus 200, Land Certus 700, Maritime Certus 100, Maritime Certus 200, and Maritime Certus 700 terminals. Land equipment is not authorized for use at sea. Maritime equipment is not authorized for use on land. Certus 100 terminals have two voice lines whereas all other terminal types have 3 voice lines. Voice quality on Iridium Certus is excellent. Each voice line can be configured as a standard line, a standard line with US number access or as a crew line for use with prepaid scratch cards.