Telephone Networks
Before we can look at how VOIP works, there are a few things that we need to know about how the regular phone system works.
Land Line phone systems transmit calls in a completley different way to how the Internet, and as a result, phone calls made over the Internet do. Phone calls made on a land Line are transmitted as an analogue signal, which means that it is a continuous wave which transmits the caller's voice. The Internet, and calls made over the Internet using VOIP, transmit using a digital signal, which is where the signal is either on or off, rather than using a continuous wave. The pictures below show the difference between the analogue and digital transmissions.
An image of an analogue signal
An image of a digital signal
As well as the difference between the way the signals are transmitted, the land Line system and VOIP use different technology behind the scenes. The land Line system uses a type of technology called circuit switching, which means when you make a call to someone a connection between your number and their number is made, and held open for as long as you are on the call. This type of technology has been used by land Line systems since they were first created over a hundred years ago. This means if you were making a call from Stirling to London, up until the 1980's your call would mean that a physical connection would be made from Stirling to London and stay connected for the time you were on the call.
Since the 1980's telephone comapnies have begun to moderinse their systems, so rather than using copper wire, the system' now, for a large part, uses fibre optic cables. It is now common that when a person makes a call their voice is digitised and sent over a much faster connection. Also, rather than holding the connection open waiting for someone to speak, the system only sends and recieves data (or in this case sounds), as and when the callers speak. This means that little packets of sound are sent out every so often rather than continuosly, so this type of system is called packet switching. Since the connection is only used every so often to send out these packets it means that the system needs only partly used connections everytime someone makes a call.
Now that we've got a basic understanding of the main difference between how VOIP works and how the land line telephone system works, we can start to look in more detail at the VOIP system.
So what exactly is VOIP?
VOIP is a fairly recent invention that allows users to make telephone calls through a digital network like the Internet. By doing this, it means that the costs of calls are either much lower than a land line company would normally charge, or in some cases even free.
There are three different versions of VOIP, which we will look at throughout this section. They are:
Click on any of the three topics above to find out more about it.
Other Services
Now that we've seen how both the traditional telephone and VOIP networks function, we can have a look at a few of the services offered on the networks. To find out about them click on them from the list below:
Been through all of the different sections? Think you've got the hang of it?
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