VoIP systems can be as simple or as fully featured as the systems they are replacing. For straightforward residential use, all that is needed to enable VoIP calls is an internet connection (preferably broadband) and an analog telephone adapter (ATA) that converts the analog signal from a traditional telephone to digital information packets for transmission over the Internet. VoIP users can also use digital VoIP telephones or VoIP cards installed on their computers.

Residential users with home networks who wish to switch to VoIP telephony will also need other equipment specific to those networks. Deploying VoIP across a home or small-business network requires the use of a router in addition to a broadband modem and VoIP-enabled telephones. VoIP gateways that include routers and modems in one unit are also available. The type of equipment you need is determined by whether your network is wireless or based on Ethernet connections.

Businesses with large networks can require quite a bit of equipment and expertise in order to completely replace their traditional telephone systems. With a combination of IP PBX systems, routers, VoIP telephones and adapters, any system can be converted to VoIP telephony. While installation costs can be considerable, the savings realized can be enormous.

An alternative means of utilizing VoIP telephony in business environments involves VoIP hosting services. These services maintain all of the equipment and infrastructure on their own premises, requiring their customers only to install VoIP telephones or adapters. Hosting services greatly simplify VoIP deployment and maintenance, but they generally charge more when compared with other VoIP providers.