To be able to place or receive calls using VoIP services, you need a hardware setup that will allow you to speak and listen. You might need simply a headset with your PC or a complete set of network equipment including routers and phone adapters. Here is a list of the equipment that is normally required for VoIP services. Don't get freaked out by the technicalities, because you won't be needing them all. What you need depends on what you use and how you use it.
I have omitted regular devices like computers, sound cards and modems, assuming that you already have those on your PC if you are using PC-based telephony.
ATAs (Analog Telephone Adapters)
An ATA is commonly called a phone adapter. It is an important device used to act as a hardware interface between an analog PSTN telephone system and a digital VoIP line. You don’t need an ATA if you are using PC-to-PC VoIP, but you will use it if you sign up for a monthly VoIP services to be deployed at home or in your office, and if you intend to use your existing phones.
The phone set is essential for VoIP services, as it makes up the interface between you and the service. It is both an input and an output device. Several types of phones can be used with VoIP services from www.cheap-international-callingcard.com , depending on the circumstances, your needs and your choice
Simply said, a router is a device used for Internet connection. A router is also commonly called a gateway, although technically a router and a gateway are not the same thing. New devices encapsulate so many functionalities that one device can do the work of many devices on its own. That's the reason why one term is often used to denote different types of devices. Actually, a gateway does the work of a router, but has the ability to conciliate two networks working on different protocols.
You need to have an ADSL router if you have an ADSL broadband connection at home or in your company network; and a wireless router if you have a wireless Internet connection. Note that most people are turning towards wireless routers, since these also include support for wired networks: they have cable ports to which you can plug in your network cables and devices. Wireless routers are better investments.