A T1 line is used for carrying information and other data between Internet service providers and private networks. T1 lines carry a variety of services from one carrier to another or customer. T1 lines are usually fiber optic cables, but some are made of copper at the ends. It can carry voice, data, images and other information through four copper wires. With multiplexing, all these can also be carried through a single circuit on a T1 line.

With a bandwidth of 1.544 megabits per second, it acts as a digital communication link and is usually supplied by a telephone company. T1 lines are the most common way of high speed Internet access and are uninterrupted by traffic from other lines. But these are not meant for individual users or for personal computers. T1 lines are used by large business concerns and some medium sized businesses which can afford them.

A T1 line is split into lesser kilobits per second communication channels to carry voice and data over networks. Also known as a DS1 line, a normal T1 line contains 24 different channels to be used for data transfer over the Internet. Typically, this will be 24, 56 or 64 kilobits per second and data transfer will be at a rate of 1.5 megabits per second. This is almost six times more data that can be transferred through a residential modem.

For normal Internet browsing, these lines can manage hundreds of users and still maintain high speed of data transfer. Even for more complicated Internet activities, these can handle multiple users without any difficulty. T1 lines typically terminate at the customers premises and ends as channel banks, TDM Mux or D/I Mux.

T1 lines have many advantages over any other means of high speed Internet access. It is universally available and has a guaranteed 247 uptime with very little chances of breakdown. They cut down on your phone bills by placing 23 phone lines for long distance service apart from high speed Internet service.