Before high-speed Internet became the chief form of Internet access, phone lines were the most common connection. The providers of phone line connections were and still are national phone line companies. Phone line Internet service is delivered on a pair of copper wires that transmit your voice as an analog signal. Most of us are familiar with a normal business or residential line from the phone company. When you use a normal modem on a line like this, it can transmit data at perhaps 30 kilobits per second.

There is one major hurdle in this phone line system. Phone companies move voice traffic as digital rather than analog signals. Therefore, your analog line must be converted to a digital signal by sampling it 8,000 times per second at 8-bit resolution. 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.

A T1 line is a high-speed digital telephone line that transfers signals at 1.544Mbps and accommodates up to 24 telephone lines or trunks. A T1 line can be used in place of separate local trunks and lines from the local telephone company. It also has the ability to bypass your local telephone company and connect directly to your long distance service provider.

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.

A T1 line might cost between $1,000 and $1,500 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.

Initial costs for T1 equipment and installation are quite high. However it may be might be a cost-effective option if you need at least 10 to 15 voice-grade channels that connect to your local or long distance service provider or host Web or FTP sites on your network or require high-capacity data bandwidth.

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