VoIP 101.com -- Info Guide to Selecting VoIP Service and Phones

VoIP Analog Adapters

You can continue to use your current analog telephone to send and receive VoIP calls, all you need is a little gizmo called an Analog Telephone Adapter, or ATA. You simply plug your phone into one end and plug the ATA into an unused Ethernet port on a broadband router or other connection point to the Internet.

An ATA will allow you to retain your current investment in analog phones, fax machines, and speakerphones. However, keep in mind that IP phones are getting cheaper all the time, and have some cool features.