A dedicated phone/data connection supporting data rates of about 43 Mbps. A T-3 line consists of 672 individual channels, each of which supports a 64 Kbps data-link. Each 64 Kbps link can traditionally support one voice conversation.

T-3 lines are used mainly by Internet Service Providers (ISPs) connecting to the Internet backbone and for the backbone itself.

T-3 lines are sometimes referred to as DS3 lines.