Avaya Definity

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This article is about the Avaya Definity PBX. For the Definity digital film recorder, see Definity.

An Avaya G3si PBX with front cover removed (view from the top).

The Definity is the latest in a line of PBX hardware manufactured since the mid 1970's by Avaya, the former Business Communications unit of Lucent and AT&T. Avaya's Communication Manager is the software which makes it work. The original Definity servers and switches can be enabled to use Communication Manager by adding a Media Server into a Definity switch. The Definity/Communication Manager has about 700 telephony features, one of the largest feature-sets compared to a Nortel Meridian, NEC's NEAX or even Cisco's CallManager.

The Definity name began in the late 1980s/early 1990s to replace the System 75 and System 85 names. The Definity Communication System Generic 2 was the former System 85 and the Definity Communication System Generic 3 was the former System 75. In the late 1990s, the Generic 3, became the new architecture for the Definity system, called the Definity Enterprise Communications Server (ECS). A stripped-down model that was similar to the ECS was called the Definity Business Communications System (BCS), was targeted towards hotels and such. Between Generic 2 (G2) and Generic 3 (G3), the G2 was a larger system with more call coverage, a larger dial plan, and more telephones can be connected to the G2 switch. However, many years later in later releases of the Communication Manager, the dial plan, the telephones connected, and attendant coverage caught up with the old G2 (System 85).

The Definity servers prior to Communication Manager use a proprietary operating system called Oryx/Pecos. The Communication Manager powered systems now use Linux. The protocol that the Definity telephones connect the switch is called the Digital Communication Protocol or DCP. Other telephones that are used in other systems, like the Merlin or Partner use a different protocol than the Definity telephones. In the Communication Manager, all endpoints now run on SIP, regardless of the telephone's protocols.

The newer Definity systems can be used with Communication Manager retains most of the features from the older models, but now it supports newer features such as IP Telephony, and mobility and unified messaging.