Which two functions are associated with a voice gateway?

Which two functions are associated with a voice gateway? (Choose two.)

A.
Switches voice channels between connected analog and digital voice circuits

B.
Provides voice-messaging services to connected analog and digital voice circuits

C.
Interconnects two logically separate VoIP networks

D.
Negotiates endpoint capabilities

E.
Controls opening and closing of logical channels that are used to carry media streams

Explanation:
The basic function of a gateway is to translate between different types of networks.
In a VoIP environment, voice gateways are the interface between a VoIP network and the public
switched telephone network (PSTN), a private branch exchange (PBX), or analog devices such as
fax machines. In its simplest form, a voice gateway has an IP interface and a legacy telephone
interface, and it handles the many tasks involved in translating between transmission formats and
protocols. The gateway allows communication between the two networks by performing tasks
such as Interfacing with the IP network and the PSTN or PBX, Supporting IP call control protocols,
Performing call setup and teardown for calls between the VoIP and PSTN networks by terminating
and reoriginating the call media and signaling, Providing supplementary services, such as call hold
and transfer, Relaying dual tone multifrequency (DTMF) tones, Supporting analog fax and

modems over the IP network.
http://www.cisco.com/en/US/prod/collateral/routers/ps5854/product_data_sheet0900aecd8016981
2.pdf