You receive a TELEX with the senders I.D. of 433863491. What type of terminal sent this message to your vessel?

Correct Answer: Option A — Inmarsat-C

Inmarsat-C mobile earth station terminal identifiers follow ITU standards by consisting of 9 digits that consistently begin with the leading digit 4, followed by the MID and subscriber numbers, identifying the message source as an Inmarsat-C system.