What is the purpose of the second I.D. in an Inmarsat-B SES?

Correct Answer: Option A — To provide an additional number which may be dedicated to computers, fax, etc.

Inmarsat-B terminals often support multiple service identifiers to allow for simultaneous or dedicated use of different communication types. A second ID provides a distinct address for peripheral equipment like fax machines or dedicated data modems, ensuring incoming traffic is routed correctly to the intended device without manual intervention.