One of the flavor of the Digital Subscription Line system that is being extensively use today is the ADSL; acronym for Asymmetric Digital Subscription Line. The copper line that is used in the telephone system used in carrying voice directly on the line is what this technology is also using. This system uses the higher frequency of the existing phone line of the telephone system, higher than the frequency of what the voice signal is using on the same system.
Without putting in or distributing more resources to lay the line for data, it provides the Telephone Service Provider an existing platform or infrastructure to run their digital and data signal. Normally, when the signal intended for the customer reaches the terminating point, it will pass thru a MODEM which converts it back from analog to digital and vice versa. Usual DSL signal uses frequency starting at around 25.875 kHz and above. On the Telephone Service Providers end, DSL terminates at the Digital Subscriber Line Access Multiplexer (DSLAM), which splits the digital signal from the voice signal and hands it to the appropriate equipment that will forwarded the signal.
Talking about the amount download speed and the upload speed and business broadband prices, this is where most of the DSL vary from other DSL technology. For ADSL the download speed is higher in accordance with the upload speed compared with other flavor of DSL.
The upstream and downstream bands are the two frequencies that are used in signaling for DSL, accordingly DSL is considered as a full duplex. The downstream band has far greater frequency range for ADSL if you compare it to upstream band. Upstream usually starts at 26.000 kHz to 136.825 kHz while the downstream starts from 138 kHz to 1104 kHz. With this in mind you can see that the downstream of ADSL is much greater than the upstream; this is because the Upload Stream is weakest in the noisiest part of the circuit while the Download Stream is strongest at the noisiest part of the circuit. Increasing the downstream signal decreases the crosstalk between other circuits in the DSLAM. SDSL on the other hand provides equal number of Upstream and downstream range of frequencies. There is an equal range of frequencies for both the Upstream and downstream for the SDSL technology.
To accommodate both the upstream and downstream signal, the voice capability of the copper wire has been removed, and that is exactly the reason why we have equal range for Upstream and Downstream. A Specialized SDSL modem is added on the local loop to convert signal and a dedicated copper line is use to connect it to the distribution line. Multiple Service Provider offers a variety of DSL for their consumers. London is no exception. There are lots of Service Provider offers broadband services in London because of it dynamic economy. Some of the major Service providers in that area are the British Telecom, O2, Sky Virgin Media and Talktalk. These different service providers are offering special products and services you can choose. All you need to do is just take some time to learn the option and prices they offer for you to adapt to your need. Other companies provide SDSL service aside from the list above.. Companeo and BTA are some of the SDSL providers in London. These companies connect their intended user from their Base location by laying out dedicated copper wires. SDSL is much more expensive than ADSL line.