Transmission System 1, T-1

T-1 is a 1.544 Mbps point-to-point, dedicated, digital circuit provided by the telephone companies. T1 lines are widely used for connecting an organization's PBX to the telephone company or a local network (LAN) to an Internet provider (ISP). Before, T-1 trunks were used only to connect major telephone exchanges, via the same twisted pair copper wire that the analog trunks used. If the exchanges were too far apart, a repeater boosted the signal. A T-1 trunk could transmit 24 telephone calls or voice channels at a time, because it used a digital carrier signal.