Telefonar através da Internet sem utilizar o VoIP

O ITSP (Internet Telephony Service Provider) é uma alternativa ao VoIP, para quem quer fazer chamadas através da Internet.

O artigo
Internet telephony and VoIP: What's the difference?
By Ted Wallingford

If you want to dive into the world of Internet telephony but prefer to use your existing phone—not VoIP software on your Mac—as your primary calling device, you might consider subscribing to an Internet telephony service provider (ITSP). An ITSP uses your broadband Internet connection to deliver telephone service to your home or office, usually at a steeply discounted rate. Unlike desktop VoIP tools, ITSPs don’t require that you use your computer to place and receive calls.
It works like this: when you subscribe to an ITSP such as Packet8, Vonage, or BroadVoice, you receive an analog telephone adapter (ATA), either through the mail or with the service bundle purchased at an electronics retailer. This ATA connects to your broadband router and your telephone, acting as a go-between and performing the signal translation that allows your analog telephone to communicate with the ITSP through your broadband connection.

in Macworld