ADSL – one of the technologies which are most extended today digital the Internet of connection (DSL) on the basis of telephone communications. The abbreviation of ADSL is decrypted as Asymmetric Digital Subscriber Line – an asymmetric digital subscriber line.
Still yesterday …
It would seem, quite recently, then still few, first owners of personal computers were content with speed the Internet of connection by a telephone line in 16 and even in 8 kb per second. The maximum speed of switched connection of dial-up by means of which an output in a wide area network was carried out did not exceed 56 kb per second. Will be to remind enough that such speed allowed to accept generally Web pages and to browse them, patiently expecting when on the monitor following opens. To download the movie in the AVI format, it was required two – three days. On movies of a DVD format even more time was required.
DSL technologies
But here DSL technologies appeared. These are technologies of high-speed digital Internet access for telephone lines. There were they in the mid-nineties as an alternative – too digital – to the subscriber termination ISDN. DSL allowed to increase considerably the throughput of a subscriber telephone line due to use of line codes and the newest methods of correction of the arising distortions. They were developed with calculation of an opportunity to function on already existing telephone lines, providing permanent connection to the Internet and not preventing at the same time operation of other subscriber's stations: phone, fax.
Today the DSL family includes more than ten technologies. Treat the main of them: ADSL, HDSL, IDSL, MSDSL, PDSL, RADSL, SDSL, SHDSL, UADSL, VDSL.
ADSL connection
Feature of ADSL technology is asymmetrical distribution of circuit bandwidth between proceeding and entering traffic. Generally during the work with the computer the user accepts information therefore more broad band of frequencies – from 138 kHz to 1.1 MHz (from the selected interval from 26 kHz – 1.1 MHz is provided to the incoming traffic.)
The ADSL technology provides the maximum speed of reception and transfer to 24 and 3.5 Mbit/sec. respectively during the maximum removal from automatic telephone exchange no more than 5.5 km. Plays a role and quality of a telephone cable.
Use of ADSL modems requires installations of the special equipment on each automatic telephone exchange, nevertheless, this technology is the most widespread in the world today. In some countries of Europe (Finland, Great Britain) it is the standard and provides the main population with inexpensive and rather fast Internet.