"Since the largest investment is in the terminals, the upgrade strategy minimizes terminal obsolescence, offering the greatest possible useful life of the users' investment. [0205] In a system such as indicated in FIG. 22, the transmitter and receiver components 2072A, 2072B and 2082A, 2082B may be switchable between data rates which are related by a factor of two, so that hardware complexity can b" . . . . .