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VoIP Phone Adapter

A VoIP phone adapter can help you lower the cost of VoIP (Voice Over Internet Protocol).

If you are considering a VoIP system for your home or office, make sure you remember your phone hardware. You already have phone sets (perhaps several, if you’re a small business). VoIP phone adapters can help you embrace the added benefits of VoIP systems while keeping your existing phones.

VoIP phone adapters will work with SIP (Session Initiation Protocol), Hosted VoIP providers or even a VoIP IP PBX (Private Branch Exchange).

What is a VoIP phone adapter?

A VoIP phone adapter converts signals. In this case, a VoIP phone adapter converts an analog signal (what your typical phone currently uses) to a digital signal (what your VoIP system uses).

Some common brands of phone VoIP adapters:

  • Linksys
  • Cisco
  • Grandstream
  • Patton

magicJack is also a type of VoIP adapter.


VoIP phone adapters allow your old and new technology to integrate so smoothly, you won’t even notice they’re there. A phone VoIP adapter ensures that your analog voice signal is converted, compressed, and transmitted. An analog telephone adapter (or ATA) is a key component if you plan to inexpensively switch your home or business phone service to VoIP.

voip phone settings

Ports, Protocols, and Codecs

If you’re eager to save money on your home or business phone system, VoIP phone adapters are the prudent choice. But with so many options, how do you make the right decision?

To select the right VoIP ATA for your particular needs, you will need to know a little bit about your current (or planned) VoIP phone technology.


There are two types of analog ports on a VoIP phone adapter: FXS and FXO. Internet phone adapters typically have either all FXS ports or a mixture of FXS and FXO ports.

FXS (Foreign Exchange Subscriber) ports are for the actual analog phones and fax machines, the subscribers to the service. How many FXS ports you need depends on how many devices you want to connect to the IP phone adapter.

FXO (Foreign Exchange Office) ports are for the analog phone lines themselves. FXO ports are often used by people or businesses that want to have an analog backup in case of a power outage. Businesses are more likely to need a VoIP ATA adapter with FXO ports than a residence or individual.

Additionally, IP phone adapters also have one or more Ethernet ports. Ethernet ports allow the converted digital signal to connect to the phone’s VoIP provider or the VoIP PBX.

What should you buy? Depends on what you need. A home or home-based small business would probably only need one or two FXS ports. A medium or larger business might typically need multiple FXS and FXO ports.


Protocols are important pieces of the Internet phone adapter puzzle. Protocols determine how the adapter and the VoIP service provider will talk with each other -- or if they will talk with each other at all.

Typically, a phone VoIP adapter will only support one protocol, but there are some that will support more than one. A SIP phone adapter is the most common type of analog telephone adapter available.

The most popular VoIP protocols are SIP (the industry standard) and SCCP or Skinny Client Control Protocol (used solely by CISCO). You may still sometimes see VoIP phone adapters using MGCP and H.323, which are both being deprecated.


Most IP phone adapters will support multiple codecs. You just need to ensure that the codecs supported by your VoIP phone adapter are the same ones supported by your VoIP service provider.

VoIP-enabled phone

Features to look for in a VoIP phone adapter

Aside from making sure that you select an IP phone adapter that supports the same protocols and codecs as your VoIP service provider, what other features should you look for?

Most VoIP phone adapters will include some or all of the following features (and more), and you’ll need to make choices according to your needs and budget:

  • Advanced Digital Signal Processing (DSP) for high-quality audio
  • Multiple protocols
  • T.38 fax support
  • Jitter buffer
  • Packet delay and loss concealment
  • Echo cancellation
  • Caller ID display/block, call waiting, and other features
  • Distinctive ringing
  • Popular codecs in the 700 range
  • Web-based management
  • Voice activity detection (VAD)
  • DHCP automatic IP assignment
  • Voicemail management

How much do VoIP phone adapters cost?

Prices for IP phone adapters can vary widely, depending on the complexity of the system, the number of FXS, FXO, and Ethernet ports, and the breadth of features available.

Simpler VoIP phone adapter systems, featuring one supported protocol and no FXO ports, can run from $15 to $50. Grandstream’s HandyTone HT502 SIP adapter with 2 FXS ports, web-based management, and T.38 fax support costs just $41.23 (Amazon.com, 1/31/12).

Other, more sophisticated ATA systems with voicemail and as many as four FXO ports can cost close to $200. The Linksys Phone Adapter PAP2, for instance, with 2 FXS ports, call waiting, call forwarding, caller ID and voicemail costs 58.99 (Amazon.com, 1/31/12). The Cisco SPA 400 SIP adapter with 4 FXO ports, caller ID, and voicemail is priced at $146.48 (Amazon.com, 1/31/12).

Commercial grade, rack-mounted systems for larger enterprises can cost well over $10,000.

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