Voice Over Internet Protacol
VOIP is best known as a way to get free calls over the internet and because of this has suffered from a reputation for poor quaity. Where you have control over the data paths between locations ( see Exstream Networks ) VOIP provides advanced bussiness features which make working very flexible.
Speech quality can be better than traditional phone lines as you have control over the quallity settings yourself. In addition it is now possible to set up remotely hosted telephone switches and as a result save money on replacing systems every few years.