ADSL stands for Asymmetric Digital Subscriber Line and is a means of transferring data via standard telephone lines. The technology allows for a much faster transfer of data than conventional voice technology. This is achieved by using all available space on the telephone line that is not being used for voice calls. This is why an ADSL filter is needed to be able to split the signal into voice and broadband. It is also due to the fact that the quality of a phone line differs, that broadband speeds are specific to individual houses. ADSL is asymmetric, which means that its download speeds are much faster than its upload speeds.