What Is a T1 Line?

A T1 line is a dedicated digital communication link from the phone company that offers as much as 1.544 megabits per second of bandwidth. This speed of communication is most often used for carrying lots of traffic to and from private business networks and Internet service providers.

More on T1 Lines

You may not be familiar with T1, since it is mostly for commercial applications, but you are familiar with a normal business or residential phone provided by the phone company. A normal phone line is usually delivered via a pair of copper wires that code and then transmit your voice as an analog signal. Pretty cool, right? When you use a normal modem on a phone line like this, that line can transmit data at maybe about 30 kilobits per second — that’s 30,000 bits per second for those of you keeping score at home.

The phone company transmits almost all of its voice traffic as a digital rather than an analog signal. As strange as it seems, your analog line gets converted to a digital signal before being transmitted. This is done by a process called “sampling” whereby your analog signal is transmitted 8,000 times per second at something like 8-bit resolution — that’s 64,000 bits per second. Still with me? Understand also that almost all of the digital data in the world is now moving across fiber optic lines laid in the last decade by phone companies, and that phone company uses different technical designations to refer to the maximum capacity of a fiber optic line.

Fiber Optic and Copper Lines

If your business has a T1 line installed, that means that the phone company you work with has hooked up either a fiber optic line or a copper line directly to your office.

A T1 line is able to carry as many as twenty four separate digitized voice channels, or the same line can carry data at a rate of 1.544 megabits per second. If the T1 line is being used only for telephone conversations, it plugs directly into the office’s phone system. By the same token, if the T1 line is carrying data it plugs into the office’s network router.

A T1 line is capable of handling 192,000 bytes per second — that’s sixty times more data capacity than a standard residential modem. You can see why businesses and high end personal servers prefer T1 service.

T1 is also known for being really reliable in terms of user overload. A T1 line is capable of handling a large service load. For general browsing needs, hundreds of users can share the same T1 line comfortably. If you have a server overload situation where a ton of users are downloading files or using high end applications at the same time, you may run into some problems, but for general use, T1 is super reliable.


This is where T1 service gets a bit problematic. A T1 line could cost you between $1,000 and $2,000 per month depending on your T1 provider and the area of service.

The other end of your T1 line has to be connected to a web server, and the total cost of a T1 line is then some combination of the fee the phone company charges and the fee that the ISP you use charges.

T1 Alternatives


A large company with many many network users will need to use a line that is a bit more powerful than T1. Here’s a list of other common line designations and their strengths.

  • DS0 – 64 kilobits per second
  • ISDN – Two DS0 lines plus web signaling at 16 kilobytes per second — that’s 128 kilobits per second
  • T1 – 1.544 megabits per second (24 DS0 lines)
  • T3 – 43.232 megabits per second (28 T1s)
  • OC3 – 155 megabits per second (84 T1s)
  • OC12 – 622 megabits per second (4 OC3s)
  • OC48 – 2.5 gigabits per seconds (4 OC12s)
  • OC192 – 9.6 gigabits per second (4 OC48s)

T1 versus Cable or EoC

T1 lines are not necessarily the wave of the future that people once thought they would be. Cable applications or Ethernet over Coax or EoC is now seen as the wave of the future. EoC is currently being developed mostly more for home or personal networking purposes, though there is some hope in the industry that EoC will surpass T1 soon for commercial purposes.

Fractional T1 Lines

Another option for businesses looking for a fast and large connection is available. High volume web customers can now install what is known as a “fractional T1 line”, which is only part of a standard T1 line.

A fractional T1 line limits the number of channels on a T1 line that you can use at a given time, saving the provider money. That provider then passes the savings on to the customer. Remember that a T1 line uses 24 channels — not all of which are always needed.

You could think of a fractional T1 line as a kind of T1 line rental — if a business wants to use the speed of a T1 connection but only needs a fraction of the 24 channels available, a fractional T1 line is the answer. T1 technology is known for its speed and ease of security.

Even though a fractional T1 line uses only a few channels of the two dozen available, these lines performance does not suffer from slower or less smooth data transmission speeds.

Fractional T1 Line Cost

As you can probably guess from the name, the fractional T1 line costs just a small fraction of the full T1 line price. Fractional T1 providers usually charge customers for each channel used, and fractional T1 costs are equal to the fraction of the full T1 line that a customer is renting.

Another benefit of fractional T1 line is you can use the security features of a T1 line (your connection with a T1 line goes directly to an ISP) and thus a fractional T1 line is way more secure than any other kind of web connection.

A fractional T1 line is still sixty times faster than a standard modem connection. This guaranteed T1 speed is possible because T1 is proprietary technology — unlike ISDN, cable, or DSL, the T1 and fractional T1 lines are specifically dedicated Internet transmission means. No one is able to “piggyback” or steal your bandwidth.

T1 lines have more than a few obvious benefits, but their high cost mean that most people who need a T1 connection simply can’t afford it.