Voip glossary

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Welcome to Simone Giustetti's wiki pages.

Languages: English - Italiano

VoIP Glossary

The world of traditional and VoIP telephony and more in general the world of technology is full of technical terms You need to understand and master in order to get the better such technology as to offer. Below You'll find a short list of terms and a brief explanation for each one. I hope the list will provide helpful to people encountering the voIP technology for the first time.


The generic term ATA defines an ATA adapter often called FXS adapter: a device used to connect an analog telephone or fax machine to a VoIP telecommunication network. In short it is the lowest possible level gateway making analog and digital devices to talk to each other.


Both FXO and FXS define a telephone socket. All telephone sockets look alike but they come in two kinds depending on their use and placement. The term FXO, an acronym for Foreign eXchange Office, defines the socket placed on telephones, fax machines, and every other device closing the telephone line circuit. Were no PBX present, the FXO of a telephone will be directly connected to a FXS socket through a cable.


Its one of the two kinds of existing telephone sockets. The socket on the wall is called FXS, an acronym for eXchange Service, and is used to bring the telephone line to destination connecting the telephone company to Your home or office. The FXS port makes the service available to users. Were no PBX present, the FXS socket will be directly connected to the FXO of a telephone through a cable.


In VoIP telephony the generic term Gateway defines a family of devices permitting to connect a digital network to traditional telephone lines. Many analog to digital converters exist and are classified according to the provided functionality and according to size and number of supported lines and users.

Two main kind of gateways exist:

  • FXO Gateway: Interfaces a VoIP PBX to the traditional telephone network thus permitting users to make and receive calls to / from the available analog lines.
  • FXS Gateway: Enables old analog devices to talk to the VoiP network making and receiving calls. Obviously not all of the services provided by the digital network will be available as the analog devices do not support them.


An acronym for Integrated Services Digital Network. It is a telephone network working almost like the traditional analog one, but transmitting digital signals instead. Voice or other signals have to be converted into a sequence of ones and zeroes before transmission and decoded once received at destination.


An acronym for Private Branch eXchange or a telephone exchange that serves a medium to large business, office or public authority. The PBX operates in the same way a telephone company does but on a smaller scale, usually limited to a building or part of one. A PBX connected to the traditional telephone line will be provided of FXO ports to connect to the sockets on the wall and of FXS ports used by telephones of fax machines.


PSTN is an acronym for Public Switched Telephone Network. It is the traditional telephone network everyone can use to make a call entering a phone number.

Languages: English - Italiano