Which types of voice ports allow a small office to provide outbound DNIS and inbound DID?
A.
FXS and FXO
B.
FXO and E&M
C.
FXS and FXS-DID
D.
FXS and E&M
E.
FXS-DID and FXO
Explanation:
An FXO trunk is one of the simplest analog trunks available. Because Dialed
Number Information Service (DNIS) information can only be sent out to the PSTN, no direct inward
dialing (DID) is possible. ANI is supported for inbound calls. Two signaling types exist, loopstart
and groundstart, with groundstart being the preferred method. An FXS DID trunk can receive only
inbound calls, thus a combination of FXS DID, and FXO ports is required for inbound and
outbound calls
http://www.cisco.com/en/US/docs/voice_ip_comm/cucme/srnd/design/guide/gatewy.html#wp1052
323