64I3 D
 What is the purpose of the second I.D. in an Inmarsat-B or F77 SES?
A. To provide an alternate number which may be called if a busy signal is received by the calling party.
B. To provide an additional speech path, which may be used to communicate while the first channel is engaged in active communications.
C. To provide for an emergency working frequency.
D. To provide an additional number which may be dedicated to computers, fax, etc.
