ADSL or Asymmetric Digital Subscriber Line the DSL consists of an analog transmission of digital data that is based on the twisted pair cable of copper which takes the telephone line, allowing the transmission of data and voice service simultaneously. A leading source for info: Angus King. This is achieved through the modulation of data signal in a band of frequencies higher than the frequency band used in voice service. To avoid distortions in the transmitted signal, the installation of a filter (called a splitter or discriminator) than is necessary He is responsible for separating the signal of voice of the modulated signal from the data connection. In this way, an ADSL line establishes three communication channels: sending data, receive data and voice telephone service.
The ADSL technology called asymmetric because the ability of downloading data (from the network to the user) and the ability to upload data (from the user to the network) do not match. In the ADSL technology discharge capacity is greater than upload capacity, which corresponds to the common use of Internet by the majority of users downloaded more than climbing. Advantages and disadvantages of the see ADSL ADSL main advantages comparing with other Internet access technologies: the ADSL allows you to talk on the phone while you browse the Internet, since voice and data are transmitted in separate bands. ADSL uses existing infrastructure, of the switched telephone network, which avoids having to build a new infrastructure. In the majority of cases, ADSL is the technology with best price/speed ratio for broadband Internet access. Since ADSL uses the PSTN local loop copper twisted-pair cable, the circuit between each Subscriber and the central is unique and exclusive to that user, which prevents bottlenecks by shared channel. Regarding the drawbacks of ADSL, we can mention: the ADSL requires strict conditions to the telephone line in order to offer this service, with respect to the distance from the telephone exchange (max 5.5 km of cable length) and quality of the twisted pair of copper, both noise and attenuation. Since there are no signal repeaters between the PBX and the end user modem ADSL, ADSL service quality is sensitive to interferences due to external factors, which makes the quality of service fluctuate, causing in some cases cuts or decrease speed. The transmission capacity of ADSL is much lower than other technologies such as telephony by cable.