DSL Modems

DSL stands for Digital Subscriber Line, a service being provided by some telephone companies, with support by some ISPs. It provides normal voice service plus simultaneous Internet access at speeds up to 1.5 Mbps (or considerably higher in some cases) using a relatively new technology that runs over standard phone lines. While a couple of years ago it appeared that ISDN would be the next generation of technology that individuals would use for higher-speed access over phone lines, now it is clear that DSL is the favored technology for consumer service due to the fairly low implementation cost. With current technology, the customer needs to be relatively close to your telephone company central office in order for DSL to work (usually about 3 miles or less).

For the type of DSL used to serve commercial businesses, the phone company installs a special wall jack near the customer PC network which is connected to the regular premises copper twisted-pair telephone wiring. A "DSL modem" (which is really a digital device rather than an actual analog modem) connects between the special wall jack and a standard Ethernet network interface card (NIC). A splitter is then installed at the Telcon box for the premises, which separates data and voice traffic -- both travel over the phone lines to the telephone company central office. At the central office the voice traffic is routed as usual to the regular Public Switched Telephone Network (PSTN), while the data traffic is interpreted by special equipment and usually routed over fiber-optic directly an ISP.

While this commercial grade of DSL service provides fast internet access, most individual users find this service too expensive for home use -- as of the beginning of 1999, typical monthly costs for the DSL phone service plus ISP DSL support were in the range of about $90 per month for 384k/128k speeds, increasing incrementally up to about $280 per month for 1.5m/384k speeds. In addition, there is usually an installation charge of $100 or more.

Newer DSL technologies have been specifically designed for consumers. These technologies, which are often referred to as "lite" versions of DSL, lower the costs of DSL service for consumers. These lite DSL technologies will have lower maximum speed capabilities (about 1 mbps maximum), but they eliminate the need for a splitter at the customer's house or work site. That means there is no need for telephone company visit to your premises to install the service, which cuts costs. These "splitterless" versions use signal-processing techniques to filter out interference. This processing can be done within your PC, or within a special modem eventually will be available through normal retail channels, getting DSL service providers out of the business of supplying and supporting end-user access equipment, and further decreasing costs. A current problem is a lack of standards between competing technologies, making it hard to mass-produce DSL modems and thus keeping their cost up. Contact your ISP and/or your phone company (or visit their web site) to see if DSL is available in your location, and to check on pricing if it is.