IP phones and Softphones

To make VoIP work, analog audio must first be converted to digital datagrams. We know
this is done by codecs. But, where is the conversion done? Where are the codecs located?
If you’re still using older analog telephones, the codecs are located in the IP PBX. Incoming
calls are digitized there, before being forwarded onto the IP network.
As an alternative, the codecs can be located in the telephones themselves. These new digital
telephones are called IP phones. Rather than having a 4-line telephone connector in the
back, they usually have an Ethernet LAN connection. An IP phone makes data connections
to an IP telephony server, which does the call setup processing.
And there’s yet another choice. Your humble computer can serve in the role of the IP
phone on your desk. You plug a headset and microphone into the computer’s audio card.
The computer’s CPU runs the software doing the codec processing, and the computer has a
LAN connection into the data network. As with an IP phone, your computer probably
relies on an IP telephony server to do call setup processing.
Now that we’ve discussed the basics of VoIP and its resemblances—and distinctions—from
the telephone network we’re all accustomed to using, we’ll next cover the potential benefits
of VoIP, and we’ll try to separate out some of the pie-in-the-sky VoIP fantasies we’ve seen
in circulation from the real returns you can expect to gather from your own implementation