Most people know what a residential line or a normal business phone line from the phone company is. A normal phone line like this is transported on a pair of copper wires that send out your voice as an analog signal. When using a normal modem on a line like this, it can transmit data at possibly 30 kilobits per second (30,000 bits per second).
The telephone company moves almost all voice traffic as digital instead of analog signals. Your analog line gets transformed into a digital signal by trying it out 8,000 times per second at 8-bit resolution (64,000 bits per second). Most of the digital data now flows over fiber optic lines, and the telephone company uses different designations to talk about the capacity of a fiber optic line.
If your office has a T1 line, it signifies that the telephone company has brought a fiber optic line into your office (a T1 line might also come in on copper). A T1 line can supply 24 digitized voice channels, or it can transport data at a speed of 1.544 megabits per second. If the T1 line is being used for phone discussions, it plugs into the office's phone system. If it is carrying data it plugs into the system's router.
A T1 line is able to carry about 192,000 bytes per second - approximately 60 times more data than a standard residential modem. It is also exceptionally trustworthy - much more trustworthy than an analog modem. A T1 line can usually handle quite a few people, depending on what they are doing. Hundreds of users are easily able to share a T1 line comfortably if they are doing some general browsing. If all of them are downloading MP3 files or video files at the same time it would definitely be a problem, but it's not very common.
The cost of a T1 line is dependent upon who is providing it and where it is going. The other end of the T1 line needs to be linked to an ISP, and the whole cost is a combination of the bill the telephone company is charging and the bill the ISP is charging.
A company of large size needs something more than a T1 line. The following table shows some of the common line designations:
- DSO - 64 kilobits per second
- ISDN - 2 DSO lines plus signaling (16 kilobits per second), or 144 kilobits per second
- T1 - 1.544 megabits per second (24 DSO lines)
- T3 - 43.232 megabits per second (28 T1's)
- OC3 - 155 megabits per second (100 T1's)
- OC12 - 622 megabits per second (4 OC3's)
- OC48 - 2.5 gigabits per second (4 OC12's)
- OC192 - 9.6 gigabits per second (4 OC48's)
For information on long-distance service with the use of T1's, please visit www.useddialers.com/longdistance.htm.
