IP Telephony is now being seen as a substitute for the old public switched phone network or PSTN landlines. At an especially basic level, the difference is that the former uses digital transmission strategies and customs, while the PSTNs are still stuck with analog signals. As a practical matter, digital data needs less space, moves quicker and is less expensive for both shoppers and the telephone company.
The way in which it works is that analog voice signals from the telefone instrument are converted into digital information and sent across as packets on networks such as the Net. They are again decoded at the other end where the call recipient then gets a voice signal. This is what is sometimes known as VoIP or Voice over Internet Protocol.
Voice, multi-media and SMS messages can all be sent and received in this fashion. In fact, the power to simultaneously send a large amount of data for different calls thru the same line is one of the defining features of IP Telephony. Since it piggybacks online, there is no cost associated for maintaining a separate network for moving the info.
What it needs is some specialized clobber to be acquired by consumers. If employed in a commercial concern with multiple telephone numbers and desks, the telephone company can offer a T1 line for establishment VoIP and data networks. Personal users can make do with a VoIP telephone.
To be particular, individual users will need broadband connectivity and either a computer or a VoIP telephone. This is rather like a wireless telephone with a base unit that plugs straight into the ADSL modem. When connecting via a P. C. employing a headphone and mike, it is simply like initiating an instant messaging voice talk with someone from an inventory of contacts.
IP Telephony is now even being used by the Telcos to route part of their data thru the Net to reduce loads on their old PSTNs. The only limitation holding back faster expansion is the lack of high speed broadband net in every corner of the Earth. As this barrier starts coming down, the PSTN and landline telephones will start fading away into history.