VoIP phone calls require a high-speed broadband connection. As a general rule of thumb, your broadband should be able to sustain an approximate rate of 80Kbps. However, if you want to use more than one VoIP line at the same time, then you should first make sure that your broadband connection can handle the additional calls. A good formula to use is 80Kbps x the number of phone lines = the sustained broadband connection speed that you will need for high quality calls. To check your current bandwidth, you can use an online tester like www.speedtest.net.