Some ITSPs (Internet Telephony Service Providers) offer a service called an SIP trunk, which allows PBX services to use VoIP (Voice-over-IP) services outside of the enterprise network via the same connection as that used for the Internet.

VoIP QoS (Voice over Internet Protocol Quality of Service) is used in VoIP services to determine a VoIP network’s overall performance and make changes to increase the customer satisfaction rate.

A MagicJack is a VoIP (Voice over Internet Protocol) device that allows users to connect their home telephones to their computer in order to make free calls. A number of influential magazines such as the L.A. Times, CNBC, PC Magazine, and the New York Times strongly recommend MagicJack.

QSIG is a signaling protocol that is  based on ISDN. It communicates signals between private branch exchanges (PBXs) within a Private Integrated Services Network (PISN) using the application-level ROSE and connection-level Q9.31 protocols.

Every office and small business needs a method of running multiple communication programs such as conference calling, video conferencing, media distribution, instant messaging, and account management software. To perform these tasks, servers need the help of a SIP gateway to bridge the gap between data streams and the Internet.

Every office needs a PBX, or Private Branch Exchange, system to operate properly. A PBX system is what drives the interconnectivity of an office's phone line network.

An IP phone is a device which uses a internet connection to make and receive phone calls.

Voice over Internet Protocol or VoIP is quickly becoming recognized as one of the leading ways of communicating over the Internet.
Skype is one of the most widely used programs for PC to PC calling with VoIP. To use Skype, it has to be installed on the computer.

An Analog Telephone Adapter (ATA), also known as the Analog Telephony Adapter, is an electronic device used to enable one or more analog telephones or facsimile machines for Voice over Internet Protocol (VoIP) calls and faxes.

IP PBX, or Internet Protocol Private Branch Exchange, is a telephony system that is used by many businesses worldwide in order to route telephone calls, especially long-distance calls, through the Internet while maintaining a wide variety of features that are available throughout an office building.