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I read that Broadband is distinguished from Baseband by using a greater range of frequencies in the electromagnetic spectrum and that ADSL divides the 1.1 MHz spectrum into 256 independent channels. However I don't really have a good mental image of what that means. Can anyone assist?

NB: Just to explain currently I'm thinking of it in terms of high or low voltages applied to a line and can't really see where frequencies would enter into it.

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If you look at an audio spectrogram you'll see a bunch of different frequencies overlaid on top of each other. Each frequency is a pure sine wave, but they combine to create more complex sounds such as the strum of a guitar, the beat of a drum, or the sound of a voice.

If you compare this with, say, the tone used by a telegraph you'll notice that more information can be encoded since more than one frequency is in use, and each frequency has its own volume which adds to the whole.

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Thanks Ignacio and Lo'oris. It begins to make sense now! – Martin Smith May 15 '10 at 12:35

They are talking about audio frequencies.

That's the reason you need to insert a filter before your home phones if the ADSL is brought to you with the same line as the phone line.

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Well, no, they are electrical frequencies. They don't become audio frequencies until you stick it through a speaker. Not that there's any speakers that can handle 1.1 MHz though... – Ignacio Vazquez-Abrams May 15 '10 at 11:59
    
oh.############ – o0'. May 15 '10 at 13:26

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