Explanation: INMARSAT-B is a digital satellite communication system. For an analog voice signal to be transmitted via such a system, it must first be converted into a digital data stream. This essential process is performed by a CODEC (COder-DECoder), which digitizes the analog voice at the transmitting terminal and then decodes (converts back to analog) the digital signal at the receiving terminal. Digitization is the foundational step for all digital voice communication. While options C and D, compression and expansion, are indeed used in digital voice systems to manage bandwidth efficiently, they are applied *to the digitized signal* by the CODEC. Digitization (A) is the prerequisite step that makes these other processes relevant for digital transmission. Option B, noise-blanking, is an optional receiver feature to reduce specific types of interference and is not a fundamental technique for processing the voice signal for transmission via a digital satellite terminal.