What is T1 Dedicated Access?


Most of us are familiar with a normal business or residential line from the phone company. A normal phone line like this is delivered on a pair of copper wires that transmit your voice as an analog signal. When you use a normal modem on a line like this, it can transmit data at perhaps 30 kilobits per second (30,000 bits per second).

The phone company moves nearly all voice traffic as digital rather than analog signals. Your analog line gets converted to a digital signal by sampling it 8,000 times per second at 8-bit resolution (64,000 bits per second). Nearly all digital data now flows over fiber optic lines, and the phone company uses different designations to talk about the capacity of a fiber optic line.

If your office has a T1 line, it means that the phone company has brought a fiber optic line into your office (a T1 line might also come in on copper). A T1 line can carry 24 digitized voice channels, or it can carry data at a rate of 1.544 megabits per second. If the T1 line is being used for telephone conversations, it plugs into the office's phone system. If it is carrying data it plugs into the network's router.

A T1 line can carry about 192,000 bytes per second -- roughly 60 times more data than a normal residential modem. It is also extremely reliable -- much more reliable than an analog modem. Depending on what they are doing, a T1 line can generally handle quite a few people. For general browsing, hundreds of users are easily able to share a T1 line comfortably. If they are all downloading MP3 files or video files simultaneously it would be a problem, but that still isn't extremely common.

The following table shows some of the common line designations:

  • DS0 - 64 kilobits per second
  • ISDN - Two DS0 lines plus signaling (16 kilobits per second), or 144 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 (100 T1s)
  • OC12 - 622 megabits per second (4 OC3s)
  • OC48 - 2.5 gigabits per seconds (4 OC12s)
  • OC192 - 9.6 gigabits per second (4 OC48s)

How does a T1 Work?

A T-1 is a dedicated data connection supporting data rate of 1.544Mbits per second. A T-1 line actually consists of 24 individual channels, each of which supports 64Kbits per second. Each 64Kbit/second channel is configured to carry data traffic. You may buy just some of these individual channels, known as fractional T-1 access.

How much does a T1 cost?

The cost for a T1 is composed of two factors.

1) The bandwidth to the Internet.

2) The loop charge from the phone company. The loop is the physical connection from the customer site to the ISP's POP (data center). The Local loop is the term utilized for the line between your house, and the local switching center. Since telephone travels on twisted pair, you can imagine one phone company line to your house as a big loop of wire, hence the name.

Our T1 Dedicated access lines typically costs anywhere from $150 to $799 monthly and the local loop charge is included..


What equipment do I need?

A T1 whether it is a fractional or full T1 requires: