A PBX (Private Branch Exchange) is a switching device that allows multiple users to share outside lines for making or receiving calls.

These are telephones that use VoIP (Voice Over Internet Protocol) technologies for making calls over both an IP Network or the traditional PSTN (Public Switched Telephone Network). SIP phones are available as either hardware or software-based. The hardware option resembles the typical telephone, but uses purpose-built hardware to receive and makes calls using the Internet. The software-based option (or otherwise known as a softphone) allows any mobile smart device or computer to be used as a telephone by means of a headset with a microphone and/or a sound card.

Unified Communications (UC) is the process in which all means of communication, communication devices and media are integrated, allowing users to be in touch with anyone, wherever they are, and in real time. These include: E-mail, chat, video, voice, presence, directory services, mobility and data.

IPT (Internet Protocol Telephony) is a term used to describe technologies that use the IP protocol to exchange voice, fax, and other forms of information, traditionally carried over the Public Switched Telephone Network (PSTN). The call travels in the form of packets, over a Local Area Network (LAN), or the Internet, avoiding PSTN tolls.

For an IPT (Internet Protocol Telephony) deployment, telephone handsets require power. This power is provided centrally via a POE (Power over Ethernet) switch. If the switch does not have POE, then power can be provided via an external AC power supply which powers each phone independently. This scenario however, is not ideal for larger deployments.