T3 Line

What Does T3 Line Mean?

A T3 line is a dedicated physical circuit that uses high-speed media to transmit data, voice and video at the rate of 45 Mbps. It offers a broadband connection consisting of 672 individual channels of 64 kilobits each.


They are commonly used in applications requiring high bandwidth, such as in research centers and big organizations, to provide uninterrupted data transmission, and other multi-channel services such as email and Internet. Other applications include Internet telephony, large file transfers, telemedicine, videoconferencing, credit card processing and more.

A T3 line is also known as digital signal level 3 (DS3).

Techopedia Explains T3 Line

T3 refers to the trunk line level 3, and is sometimes used interchangeably with DS3 (digital signal level 3). In practice, the DS3 signal is transmitted over a T3 physical line, consisting of a fiber optic cable or coaxial cable. The T3 lines, which are symmetrical and duplex, have equal speeds on both upload and download, and therefore allow simultaneous transmissions without clogging the data lines.

A T3 line is an ideal connection for big business, however, small businesses that cannot afford the full 45 Mb or who may not need such a high capacity, have an option of buying a fraction of the full T3 line. The fractional T3 has some of the 28 lines turned off, and has a lower capacity such as 10 or 20 Mbps.

T3 lines are available in different modes and the choice is determined by the organization’s structure, needs and budget.

  • T3 for Internet — This is a fractional or full, clear channel for Internet access, available in 10, 20, 30 and 45 Mbps. Fractional T3 can be downgraded or upgraded to meet fluctuating demands.
  • Point-to-point or private (VPN) — Provides a secure and private connection for high speed and integrated data, video and voice services between company offices in different locations
  • Tiered T3 — A pay-as-you-go option
  • Burstable T3 — A flexible option where companies pay for only what they use, and is upgradable at 3 Mbps increments
  • Bondable T3 — Combines several T3 lines to provide a massive bandwidth. The lines are configured to use a single line or combined using a router.

Typical applications include:

  • High-speed connection between the customer and the ISP, or between two customer locations
  • Providing fast data throughput to locations not served with fiber networks
  • Virtual private networks with data, video and voice services for research labs, financial institutions, universities, health care providers and other heavy data users

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Margaret Rouse

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.