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 connect directly to a standard telephone, fax machine, or sililar device and supplies ring, voltage, and dial tone
C.the FXS interface connect directly to an IP phone and supplies ring, voltage, and dial tone
D.the FXS interface connect directly to ISDN voice channels