What Is Different Between Phone Call and VIOP?

VOIP stands for voice over IP. In a standard telephone setup, you are assigned a phone number specifically for your line. When you place a standard phone call, you are telling a local phone switch, how to connect your call to the local central office, on the communications network. The network is tied together using large scale switches such as the 5ESS Switch which is the Class 5 telephone switching system by Lucent Technologies. You call is electronically routed to the specified location, but the actual transmission of the voice signal is done in a combination of compter and analog audio signaling and amplification.

In the case of VOIP, the communication is transferred in groups of numbers (digital signals) which if printed out would look like large charts of numbers. These are "packets" of information and are handled using a protocol called TCP/IP, or transmission control protocol / internet protocol, which allows the assigning of your VOIP number to whatever IP address exists on the internet conneciton you are currently using. In other words, you can move your VOIP phone to any location where there is an internet connection. With VOIP, the sound of your voice is recorded, compressed into small clumps of computer information, and sent over the network. The communication is this case is not only handled by the telecommunications infrastructure, but is also handled over the internet.

A typical 5ESS switch
http://text.dslreports.com/r0/download/134522~d1fb96b54c2dd52692efc97f48ef399b/5ess.jpg

Voip systems are much more scalable and can range from small desktop setups for a small office, or can be enormous like the following datacanter
http://pics.computerbase.de/1/4/8/5/7/1_m.jpg

http://en.wikipedia.org/wiki/Telephone_exchange
http://www.packetizer.com/voip/papers/understanding_voip/