Digital subscriber line facts for kids
| DSL technologies | |
|---|---|
| Standard | |
| ADSL | ANSI T1.413 Issue 2 ITU G.992.1 (G.DMT) ITU G.992.2 (G.Lite) |
| ADSL2 | ITU G.992.3/4 ITU G.992.3 Annex J ITU G.992.3 Annex L |
| ADSL2+ | ITU G.992.5 ITU G.992.5 Annex M |
| HDSL | ITU G.991.1 |
| HDSL2 | |
| IDSL | |
| MSDSL | |
| PDSL | |
| RADSL | |
| SDSL | |
| SHDSL | ITU G.991.2 |
| UDSL | |
| VDSL | ITU G.993.1 |
| VDSL2 | ITU G.993.2 |
DSL (which stands for Digital Subscriber Line) is a clever way to send digital information, like internet data, over regular telephone lines. Think of a phone line as a road. Usually, only voice traffic uses it. But DSL uses other "lanes" on that same road for internet data.
This internet data is combined onto the phone line. At both ends of the line, a special device called a splitter or DSL filter helps separate the voice part from the internet data part. This means you can talk on the phone and use the internet at the same time!
Most DSL connections for homes are asymmetric. This means the speed for downloading things (like watching videos) is faster than the speed for uploading things (like sending emails). This type of DSL is called ADSL. Sometimes, there's also Symmetric DSL (SDSL), where upload and download speeds are the same, but it's less common for homes.
At your house, a modem converts the internet signals to travel on the phone line. At the other end, usually at your internet provider's office, a device called a DSLAM combines many signals from different homes onto the main internet network.
How DSL Works
DSL, especially VDSL (Very high-speed Digital Subscriber Line), works by dividing the frequencies on a single phone line. Imagine the phone line has different "channels" or "bands" for signals.
- The internet data from your ISP uses the high-frequency channels (above 25,000 Hertz).
- Your voice calls use the lower-frequency channels (below 4,000 Hertz).
You usually put a small DSL filter on each phone in your house. This filter makes sure your phone only uses the low frequencies for voice. This way, your DSL modem and your regular phone can both use the same line without getting in each other's way.
DSL Equipment
The equipment you use at home for DSL is often called a DSL modem. It's also sometimes known as a Terminal Adapter. This modem changes the digital data from your computer into a signal that can travel over the phone line. It also changes the signals coming from the phone line back into digital data for your computer.
Sometimes, the DSL modem is combined with other useful features. It might include a router to share the internet with multiple devices, or a firewall to protect your computer. When it has these extra features, it's often called a DSL router or DSL gateway.
Images for kids
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A DSL chip
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An example of a DSLAM from 2006
See also
In Spanish: Línea de abonado digital para niños
