There are three types of PBXs.
Analog PBX
Analog PBXs send voice and
signaling information as actual analog sound. The
information never gets digitalized. Each hope will
listen to the call before it directs it further.
A VoIP gateway is required to
connect Exchange Unified Messaging or OCS
Mediation Server with Analog PBXs.
Digital PBX
Digital PBXs encode analog sound
into a digital format. They typically encode the voice
using a standard industry audio codec, G.711. Once
encoded the digitized voice is sent on a channel using
circuit switching.
Digital PBXs can also support analog trunks.
Circuit switching sets up an end-to-end open connection.
It leaves the channel open for the length of the call
and for the callers’ exclusive use.
A VoIP gateway is required to
connect Exchange Unified Messaging or OCS
Mediation Server with Digital PBXs.
IP PBX
IP PBXs are designed to carry voice
over IP (data) networks. The IP phone contains a Network
Interface Card so it is part of the network. The phone
converts voice into digitized packets and then puts the
digitized packets onto the data network. The voice
packets are sent via packet
switching, a technique which lets a single
network channel handle multiple calls.
There is no need of a VOIP gateway
to connect Exchange UM with IP PBX. Exchange UM can
directly talk to the IP PBX.
Hybrid PBX
Hybrid PBXs generally provide both
Digital and IP PBX capabilities. This hybrid approach
allows a customer to run a mixture of digital and
IP-based communications.
Supported Gateways for Office
Communications Server 2007
