This is the working principle of the modem. The device that connects the computer system or router to a telephone line via cable wires to provide digital subscriber line service to the system is called DSL modem connection.
The telephone connection is not interrupted and the device works efficiently even if the telephone connection is used. This is a way of business for telecom companies. The frequency of telephone and DSL connection is different and this is the reason why telephone works even if the internet is being used. It is important to know the working of telephone lines and connections to know about DSL. Telephone connections are made through wires that may be underground or not.
These wires have a capacity more than that of normal telephone frequency. Hence, DSL is used in the telephone lines with a different frequency so that an internet connection is also enabled in the same lines. Hence if we consider the period of DSL usage introduction and the telephone introduction, we could say that telephone cables were wasted for nearly a century with the use of less frequency.
A specific modem is needed for DSL connection and it works only for the same. A splitter is used so that the voice and the data connection is separated from the telephone lines. Data is sent through ADSL lines which is specifically used so that the data connection is faster for download than for upload. It is to be noted that similar to other modems, the modem and ISP hub should be kept close so that the connection is faster always.
If we stay away from the modem, the speed of the data connection will be worse. As discussed in the above points, two equipment is needed for the DSL connection. A modem and a splitter make the DSL connection a better one.
The modem is supplied either by the company or by the router that works for the DSL connection. It is designed in a way that if we change from one ISP and if we change the connection, it may not work well.
Splitter purpose is understood from the name as it separates the data connection and voice modulation. You plug your computer into the modem , and the modem plugs into a splitter to separate the voice from internet data as I mentioned above.
The lines will run from your wall to outside to the ISP hub. The lines that are used to send data back and forth are, in most cases, ADSL lines. This means Asynchronous DSL, which in English means that one side of the line download is bigger than the other side upload.
One important thing to note is that the farther away your connection is from the ISP hub, the worse the quality and speed of your connection will be. Most of it will be supplied by your ISP anyway. The internet provider usually supplies this, and sometimes the router too. The answer lies in small amplifiers called loading coils that the telephone company uses to boost voice signals.
Unfortunately, these loading coils are incompatible with ADSL signals, so a voice coil in the loop between your telephone and the telephone company's central office will disqualify you from receiving ADSL.
Other factors that might disqualify you from receiving ADSL include:. There are two competing and incompatible standards for ADSL. CAP operates by dividing the signals on the telephone line into three distinct bands: Voice conversations are carried in the 0 to 4 KHz kilohertz band, as they are in all POTS circuits.
The upstream channel from the user back to the server is carried in a band between 25 and KHz. The downstream channel from the server to the user begins at KHz and goes up to a point that varies depending on a number of conditions line length, line noise, number of users in a particular telephone company switch but has a maximum of about 1.
This system, with the three channels widely separated, minimizes the possibility of interference between the channels on one line, or between the signals on different lines. DMT also divides signals into separate channels, but doesn't use two fairly broad channels for upstream and downstream data. One way to think about it is to imagine that the phone company divides your copper line into different 4-KHz lines and then attaches a modem to each one.
You get the equivalent of modems connected to your computer at once. Each channel is monitored and, if the quality is too impaired, the signal is shifted to another channel. This system constantly shifts signals between different channels, searching for the best channels for transmission and reception. In addition, some of the lower channels those starting at about 8 KHz , are used as bidirectional channels, for upstream and downstream information.
Monitoring and sorting out the information on the bidirectional channels, and keeping up with the quality of all channels, makes DMT more complex to implement than CAP, but gives it more flexibility on lines of differing quality. These filters are low-pass filters -- simple filters that block all signals above a certain frequency. Since all voice conversations take place below 4 KHz, the low-pass LP filters are built to block everything above 4 KHz, preventing the data signals from interfering with standard telephone calls.
ADSL uses two pieces of equipment, one on the customer end and one at the Internet service provider, telephone company or other provider of DSL services.
At the customer's location there is a DSL transceiver , which may also provide other services. Regardless of what it's called, it's the point where data from the user's computer or network is connected to the DSL line. The transceiver can connect to a customer's equipment in several ways, though most residential installation uses USB or 10 base-T Ethernet connections. While most of the ADSL transceivers sold by ISPs and telephone companies are simply transceivers, the devices used by businesses may combine network routers , network switches or other networking equipment in the same platform.
A DSLAM takes connections from many customers and aggregates them onto a single, high-capacity connection to the Internet. Because cable-modem users generally share a network loop that runs through a neighborhood, adding users means lowering performance in many instances.
ADSL provides a dedicated connection from each user back to the DSLAM, meaning that users won't see a performance decrease as new users are added -- until the total number of users begins to saturate the single, high-speed connection to the Internet. At that point, an upgrade by the service provider can provide additional performance for all the users connected to the DSLAM. This site can provide information on ADSL service companies in your area, the rates they charge, and customer satisfaction, as well as estimating how far you are from the nearest central office.
Next, we'll look at ADSL alternatives. There are lots of variations in DSL technology -- many of them address DSL's distance limitations in one way or another. Other types of DSL include:. With DSL's distance limitation and lower availability, what are some other options?
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