What is ADSL?#
ADSL stands for Asymmetric Digital Subscriber Line. It sends data over the same copper telephone wire without tying up the line for voice calls. "Asymmetric" means download speed is higher than upload speed, because most users download more than they upload.
How does it work?#
The higher frequencies of the phone line are used for data and the low frequency for conversation. At home, a splitter separates them: one output goes to the phone and one to the modem. The ADSL modem converts the signal into usable data.
Factors that affect quality#
- Distance to the exchange: the farther it is, the lower the speed.
- Wire and connection quality: old or damaged wire brings noise and dropouts.
- Interference: from electrical appliances or neighboring lines.
- Congestion: capacity may drop at busy hours.
Today's situation#
With the arrival of fiber, ADSL is gradually being retired, but it is still common in areas without fiber. Its better successor, VDSL, gives higher speed over copper but with shorter reach.
A practical note#
If your ADSL connection keeps dropping, first check the splitter, cable and phone socket and restart the modem. If it continues, ask your provider to test the line.