From VTwiki

ViaTalk Basic Service Requirements

To use ViaTalk, you will need an existing high speed internet connection such as broadband cable or DSL.  While both satellite internet and wireless internet service such as microwave or WiMAX are considered broadband internet services, they operate differently than hard-lined internet service providers and because of the nature of wireless internet, customers of these service providers are strongly urged not to use VoIP.  To experience the highest voice quality over ViaTalk, a minimum bandwidth of 200 Kb/s for both download and upload is required.

 

In addition to the modem provided by your internet service provider, you will need to have a router on your network to be able to connect both your computer and your ViaTalk phone adapter at the same time.  Please note that some DSL and cable modems are both a modem and router combination.  If you are unsure of whether or not your modem is also a router, check for multiple ethernet ports.  If your modem has more than one ethernet port, it is also a router.  These devices are also called gateways.

 

Touch tone phones are also a requirement as pulse phones are not compatible with ViaTalk's service.