Analog telephony adapter

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An analog telephony adapter, or analog telephone adapter, (ATA) is a device used to connect one or more standard analog telephones to a digital and/or non-standard telephone system such as a Voice over IP based network.

[edit] Form

An ATA usually takes the form of a small box with a power adapter, one Ethernet port, one or more FXS telephone ports and may also have a FXO link. Users can plug one or more standard analog telephone devices into the ATA and the analog device(s) will operate, usually transparently, on a VoIP network.

[edit] Purpose

ATAs are used by many VoIP companies selling a telco-alternative VoIP service, where the device is used to replace a user's connection to a traditional telephone company. When sold in connection with a VoIP service, the ATA is often locked so it cannot be used with a competing service, and the user can only partly change its configuration. Some providers do sell devices that are not locked and can be used with any compatible provider.

[edit] FXS to Ethernet gateways

The most common ATA is a box with at least one Foreign eXchange Station (which includes a telephone jack), used to connect a conventional telephone, and an Ethernet jack used to connect the adapter to a LAN. Using such an ATA, it is possible to connect a conventional telephone to a remote VoIP server. The ATA communicates with the server using a protocol such as H.323, SIP, MGCP, SCCP or IAX, and encodes and decodes the voice signal using a voice codec such as G.711, G.729, GSM, iLBC or others. Since the ATA communicates directly with the VoIP server, it does not require any software, such as a softphone, to be run on a personal computer.

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