Explanation: The Iridium satellite communication system provides global coverage using a constellation of Low Earth Orbit (LEO) satellites. It is fundamentally a **digital** system, meaning all voice and data transmissions are converted into digital signals before being sent over the air. This digital nature allows for efficient use of spectrum, robust error correction, and secure communications. The standard, circuit-switched services offered by Iridium include digital voice and low-speed data. The basic data rate for these services, including data over the voice channel, is **2.4 kbps**. While Iridium offers higher speed internet services through specific data terminals, the core voice and general data service over the handset is at this rate. Therefore, options claiming "analog voice" are incorrect because Iridium uses digital modulation. Options with higher data rates like 4.8 kbps or 9.6 kbps are incorrect for the system's fundamental voice and basic data services.