Question 3-97P6

INMARSAT-M was an early digital mobile satellite service designed for compact, portable terminals. It provided a range of fundamental communication capabilities by employing digital compression techniques to optimize satellite bandwidth usage. * **Voice at 6.2 kbps:** This reflects a low-bitrate digital voice codec, crucial for efficient spectrum use over satellite links, allowing for acceptable voice quality within limited bandwidth. * **Data at 2.4 kbps and Fax at 2.4 kbps:** These rates represent the synchronous digital data and Group 3 fax capabilities, again chosen for efficiency in the context of mobile satellite communications at the time. * **E-mail:** This is an application service provided over the digital data link. Options A and D are incorrect because they omit voice services, which were a primary feature of INMARSAT-M, and list different data/fax rates. Option B is incorrect because INMARSAT-M was a digital service, so "Voice at 3 kHz" describes an analog bandwidth, not a digital bitrate, and its data/fax rates are also inaccurate for the service.