T1 Line

What Does T1 Line Mean?

A T1 line is a dedicated transmission connection between a service provider and client. It uses an advanced telephone line to carry more data than a traditional standard analog line that carries a single channel of data at 64 Kbps.


T1 line speed is consistent and constant. A T1 line can carry 24 voice channels for telephone calls or digital data at a rate of 1.544 Mbps, and with usage of compression, carried channels double to 48.

Techopedia Explains T1 Line

Developed by AT&T Bell Laboratories in the late 1960s, traditional T1 lines use copper wire, but most new installations use optical fiber. T1 lines use pulse-code modulation, which allows coder and decoder sharing by multiple voice trunks. Channels are preconfigured to carry voice traffic or Internet data.

Clients lease full or fractional T1 lines. Fractional T1 lines do not experience performance degradation, even though only a few channels are used. T1 lines are proprietary, which reduces congestion and ensures usage by only one client, versus cable, digital subscriber line (DSL) and Integrated Services Digital Network (ISDN).


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Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.