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DSL Technology
How does DSL Internet allow customers to access the Internet at speeds up to 50 times faster than conventional analog modems and receive a telephone call at the same time?
A special DSL Internet modem, which allows data traffic to move at speeds up to 1.54 Mbps, connects to an ethernet network interface card (NIC) in your PC. The DSL Internet modem then plugs into a customized wall jack connected to the regular telephone wiring inside the building, which consists of a twisted pair of copper wires. At the point where the telephone wire leaves the building on its way to the Southwestern Bell Telephone Company Central Office (CO), or the Point of Demarcation, a splitter attaches to the line separating the data and voice traffic.
The digital data and analog voice then travel over telephone lines to a nearby Southwestern Bell Telephone Company Central Office (CO). There, the voice service or Plain Old Telephone Service (POTS) is sent to the Public Switched Telephone Network (PSTN). The data traffic is interpreted by special equipment called a DSLAM (DSL Access Multiplexor) and routed over Southwestern Bell Telephone Company's robust fiber-optic ATM network to Southwestern Bell Internet Services (see diagram below).
- Because DSL Internet Access operates on your regular phone line, a power failure will not impede your ability to use your phone to make a call.
- Utilizing the telephone line guarantees a point-to-point connection for DSL Internet service, making it more secure than cable modem connections.
- Point-to-point connection for DSL Internet service means your Internet connection is always available.
- DSL Internet is compatible with regular voice service such as voice mail and custom calling features.
- Speeds up to 1.544 Mbps. The following is an approximate speed comparison among several data technologies:
| Technology | Analog Dial-up | ISDN | DSL Internet |
|---|---|---|---|
| Downstream Speed | 28.8 Kbps | 128 Kbps | up to 1.5 Mbps |
| Image File (2 MB) | 70 seconds | 17 seconds | 1 second |
| Complex Image (16 MB) | 9 minutes | 2.4 minutes | 11 seconds |
| Short Video (72 MB) | 41 minutes | 10 minutes | 48 seconds |
