Type of broadband telecommunications connection (see broadband technology ) used especially to connect Internet service provider s to the Internet's infrastructure.
Developed by Bell Labs in the 1960s, the "T-carrier systems" offer entirely digital, full-duplex exchange of data over traditional wire, coaxial cable, optical fibre, microwave relay, or other communications media. The T1 lines carry about 1.5 megabits of data per second, while the related T3 lines carry over 40. However, such systems are generally too expensive for individual network users, who turn instead to ISDN lines, cable modem s, DSL connections, or some form of wireless or satellite system for high-speed Internet access.