When looking to make a start with, or even after using internet telephony, It can be quite confusing when you see the many acronyms that are associated with it. 

This FAQ aims to identify the common acronyms, and explain what they mean, to make it easier to understand how they work together:

• VoIP - Voice over Internet Protocol

  • This is the term used in reference to almost any telephony that is established and provided through the internet.

• SIP - Session Initiation Protocol

  • This is the most common protocol that defines how multimedia endpoints communicate with each other and establish calls, whether they be phones, voice servers, messaging applications etc. 

• PBX - Private Branch eXchange

  • A private telephone network used within a company or organisation. The users of the PBX phone system can communicate internally (within their company) and externally (with the outside world), using different communication channels like Voice over IP, ISDN or analog.

• PSTN

  • The world's collection of interconnected voice-oriented public telephone networks - PBX’s and Internet Telephony Service Providers (ITSP) forward user calls to the PSTN to be connected to remote phones.

• ITSP

  • Internet Telephony Service Providers (ITSPs) offer digital telecommunications services based on Voice over Internet Protocol (VoIP) that are accessed via the internet.

• IVR

  • Interactive Voice Response (IVR) is a technology that allows a computer to interact with callers through the use of voice and key tones input via a telephone keypad.

• CID

  • Caller Line Identity (CID) is a combined unit of information containing the name and number of a caller, usually sent to the caller’s phone when a call is being established, normally used to identify who is calling.

• DDI / DID 

  • Direct Inward Dialing (DID), also called Direct Dial-In (DDI) is a technology commonly provided by ITSPs to send calls directed to different numbers over the same VoIP connection. The identity of the number dialled is usually sent with the call data initially being sent.

• DTMF: Dual-Tone Multi-Frequency

  • Dual-Tone Multi-Frequency (DTMF), sometimes called "Touch Tone" dialing, refers to the popular keypad and dial tones that most phones use to send information about what key was pressed on the number pad to the remote party.

• UC or UCaaS: Unified Communications or Unified Communications as a Service

  • Unified Communications (UC) or Unified Communications as a Service (UCaaS) is the integration of various communications services such as voice, video conferencing, email and voicemail under a single user interface. Many PBX systems employ UC Technology.