A.The FXS interface allows an analog connection to be directed at the public switched telephone network （PSTN’s） central office.
B.The FXS interface connects directly to a standard telephone，fax machine，or similar device and supplies ring，voltage，and dial tone.
C.The FXS interface connects directly to an IP phone and supplies ring，voltage，and dial tone.
D.The FXS interface connects directly to ISDN voice channels.

A.Standard encoding techniques create an uncompressed digital data rate of 4000 bps.
B.Standard encoding techniques create an uncompressed digital data rate of 8000 bps.
C.Standard encoding techniques create an uncompressed digital data rate of 64，000 bps.
D.Voice quality is not a concern if compression is not used.
E.Two methods of quantization are linear and logarithmic.
F.Two methods of compression are u-law and a-law.