Digital Subscriber Line

A Digital Subscriber Line (DSL) is used to transmit digital data over telephone lines. It offers high speed Internet services through broadband connections. DSL transmits data at speeds of up to 160 kbps over copper lines. DSL modems are connected to the computer through a Universal Serial Bus (USB) or a 10-base T connection. A DSL Access Multiplexer (DSLAM) accepts connections from various users and converts them in to a high capacity Internet connection. DSL separates channels for phone and data transfer.

There are various types of DSL available including Asymmetric DSL (ADSL), High bit-rate DSL (HDSL), Integrated Services Digital Network (ISDN), Rate- adaptive DSL (RADSL), Symmetric DSL (SDSL), and Very high bit rate DSL (VDSL).

The cost of DSL varies by package and service provider. Almost all broadband providers offer the service at the rate of about $40 to $92 per month. Some companies offer packages that range between $15 and $25 per month, especially for new users.


DSL offers many benefits. By using a DSL Internet connection, you can ensure a highly reliable and secure connection. You can also use the phone line simultaneously with Internet. The distant sensitive technology enables uninterrupted Internet connections. DSL provides high speed data communication and specialized network access. No extra phone line is necessary for accessing this connection. Since it uses dedicated lines, Internet access is private and stable with fewer delays.

How It Works

In DSL, voice and data is transferred simultaneously over a twisted pair of copper telephone lines. DSL usually runs on top of the copper phone lines. Normal voice calls use a small portion of the frequency range that is available in the phone line and the DSL uses the frequencies above the range of the voice calls to send data back and forth without interfering with the ongoing phone call.

The data from the computer is sent along the DSL line to your phone company office (CO), where it splits off from the normal voice traffic and is sent straight to the modem. At the CO, a DSL Access Multiplexer (DSLAM) aggregates incoming lines. It then transfers the voice traffic to the Public Switched Telephone Network (PSTN) and the data to a high speed digital line that connects to the Internet.

A DSL modem divides available bandwidth from a telephone line using frequency division multiplexing (FDM). In this FDM one frequency is for upstream data and another for downstream data. The downstream data is then divided into high and low speed channels and upstream for low speed channels. To use this FDM, you need DSL Splitters (separate low frequency signals and high frequency signals) so that the two signals do not interfere with one another.


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