The ATA, Its Features and Functions

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An ATA is a device which acts as a hardware interface between a PSTN analog phone system and a digital network or VoIP service. Using an ATA, you can merge your PSTN phone system and VoIP service, or connect a LAN to your phone network.

An ATA normally has two sets of outlets: one for your VoIP service or LAN and another one for your conventional phone. Obviously, on one side, you can connect and RJ-45 jack (VoIP or Ethernet cable) and on the other, a RJ-11 (phone line cable) jack.

An ATA links with the remote VoIP Service Provider’s service using a VoIP Protocol such as SIP or H.323. The encoding and decoding of voice signals are done using a voice codec. ATAs communicate directly with the VoIP service, therefore there is no need for software, and hence no need for a computer, although you can connect one to a computer or a softphone.

Features of an ATA

The most common features of an ATA are:

  • Ability to support VoIP protocols. The more protocols one can support, the better it is. SIP and H.323 are supported on all new ATAs today.
  • Ports: An ATA should provide at least one LAN (RJ-45) port and one RJ-11 port, so as to make the interface between the phone network and the VoIP service. Some ATAs even provide additional ports, like for example, a RJ-45 port to connect to a computer. You can use this to do phone-to-PC calls. Some ATA’s have USB ports which allow them to more easily connect to computers and other devices.
  • Call Switching: Many people use PSTN and VoIP interchangeably. The call switching features in the ATA allows you to easily switch between these two.
  • Standard Service Features: It is common and practical today to have several service features like Caller ID, Call Waiting, Call Transfer, Call Forwarding etc. A good ATA should support all these.
  • 3-Way conferencing: Many ATA’s come with 3-way conferencing support, which allows you to talk to more than one person at the same time. This proves to be very useful especially in a business context.
  • Power failure tolerance: The ATA runs on electric power. It normally stops working in case of a power cut. This should not mean that your communication should be completely paralyzed. A good ATA should automatically switch to PSTN line default in case there is a power failure.
  • Voice qualityATA manufacturers are sharpening their saws day after day. Some ATAs provide superb hi-fidelity voice quality with enhanced technologies like Digital Signal Processing (DSP).
  • Interoperability: In a company context, an ATA may be part of an already-complex hardware structure. For this reason, a good ATA should be compliant and interoperable to a maximum with other hardware devices. These are only the most common features that should make a good ATA. Modern ATAs come with a large number of additional features. Have a close look before you buy.

Figure 1 shows what a typical ATA looks like.