Now multiplexing does this by dividing the telephone

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Now multiplexing does this by dividing the telephone line's bandwidth into two signal ranges, effectively creating two channels. The first channel is used for your standard telephone voice communications and it uses frequency ranges less than four kilohertz. The second channel is used for DSL communications and it uses frequency ranges four kilohertz and above. Now, this division of the phone line into two channels does cause some
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problems that you have to account for when implementing a DSL connection. For example, traditional telephones are not DSL aware. They aren't able to distinguish between the two channels on the line. They try to accept and process both signalsas if they were one and you get a lot of interference from the DSL communications. So to fix this, you need to implement a DSL filter on the telephones. And this filter blocks DSL communications and just allows telephone frequencies through. Now, DSL providers frequently offer two different types or levels of DSL service. The first type is called asymmetric DSL, we simply call it ADSL. With ADSL the upload speeds and the download speeds are not the same, they're asymmetric.That's why we call it asymmetric DSL. Now ADSL will typically provide very fast download speeds but incredibly slow upload speeds. This allows you to access web pages, stream movies or download large files at relatively fast speeds. However, uploading files is not nearly so fast. For example, if you are attaching a large file to an emailor trying to save files to a cloud server you'll find that the connection is a lot slower going that direction. Now there is a second type of DSL called symmetric DSL or SDSL and as its name suggests, SDSL uses the same upload and download speeds that's why we call it symmetric. Now, ADSL is much cheaper than SDSL. However, if faster upload speeds are required for a particular implementationthen SDSL should be used over ADSL. Now, DSL Internet connections require a special device called a DSL modem to connect the local network to the service provider's network. Integrated Services Digital Network (ISDN) 4:00-5:33 The next type of Internet connection we're going to talk about is similar to DSL in a lot of ways. It's called the integrated services digital network or just ISDN. Now, ISDN is kind of halfway between dial-up and DSL and frankly it never really gained much popularity in North America due to several factors. It did however see widespread implementation in Europe. Now similar to DSL, ISDN connects to the internet using standard phone lines and uses multiplexing to divide those lines into multiple communication channels. Now ISDN offers two different levels of service. The basic level of service is called BRI, which stands for basic rate interface.
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