A telephone VoIP adapter (TVA), also called digital telephone adapter, is a device that interfaces digital private branch exchange (PBX) telephone sets to a Voice over Internet Protocol (VoIP) network, using, for example, the Session Initiation Protocol.
An analog telephone adapter (ATA) converts an analog telephone port (Foreign exchange station, FXS) to a VoIP network.
Some telecom manufacturers have produced hybrid exchanges with TVA-like elements that support IP telephones and also have units or cards that allow connection of digital telephones.
Whether a standalone TVA or a hybrid PBX is deployed, the intention is to preserve investment in an installed base of telephones, and eliminate the need to install Ethernet network infrastructure.
This article related to telephony is a stub.