How does a T1 line work?
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, also called a dial-up line,it can transmit data at perhaps 30 kilobits per second (30,000 bits per second).
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 also be integrated or split and used for both voice & data.
A T1 line can carry about 195,000 bytes per second -- about 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.
A T1 line might cost between 500.00 and 1500.00 per month depending on who provides it and where it goes. The other end of the T1 line needs to be connected to a web server, and the total cost is a combination of the fee the phone company charges and the fee the ISP charges.
A large company needs something more than a T1 line. The following list shows some of the common line designations:
- DS0 - 64 kilobits per second
- ISDN - Two DS0 lines plus signaling (16 kilobytes per second), or 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)