Broad Band Connections and Transmissions

  RegPerring 19:19 20 Feb 06
Locked

I've just started to make an attempt at understanding how the internet works, but I don't understand how a broad band connection is set up on a previous dial up connection and how the transmissions actually take place.

Am I correct in assuming that BB is simialr to the digital TV transmission?

So if BB is a digital transmission and dial-up is an analogue transmission, I then ask myself, why was there a need to use dial-up? After all the signal from a PC is digital so why convert it to analogue for the transmission? Obviously there must be something necessary for a direct digital transmission from a PC onto the internet - so what exactly is it?

  keewaa 20:30 20 Feb 06

and I don't understand your question.

A dial up connection is completely different from a Broadband connection. A dial up connection can be made on any ordinary telephone line.

A Broadband connection must be enabled first (by BT or your ISP) , so that there is a broadband signal coming down your telephone line. Basically they are different types of signal coming down and up your telephone line.

Are you talking about a satellite broadband connection, where the download signal comes from the satellite and the upload signal goes up the phone line?

  ade.h 21:00 20 Feb 06

Assymetric (or Symetrical) Digital Subscriber Line. The operative word being digital, which is probably why you are thinking about digital television signals.

A digital signal - in simple terms - is just a bunch of 1s and 0s.

  RegPerring 01:43 21 Feb 06

You said:
"dial up connection is completely different from a Broadband connection. A dial up connection can be made on any ordinary telephone line."

Yes I am aware of that but how are the connections different - are different cables used for connecting to telephone exchanges and then to ISPs?

You said:
"A Broadband connection must be enabled first (by BT or your ISP) , so that there is a broadband signal coming down your telephone line. Basically they are different types of signal coming down and up your telephone line."

So how do they differ?

You said:
"Are you talking about a satellite broadband connection, where the download signal comes from the satellite and the upload signal goes up the phone line?"

I was referring to cable connections for both digital TV and internet. I am aware of satellite TV which broadcasts digital TV, but never knew they also did broadband also.

thanks for your attention,
Reg.

  RegPerring 01:46 21 Feb 06

You said:
"Assymetric (or Symetrical) Digital Subscriber Line. The operative word being digital, which is probably why you are thinking about digital television signals.

A digital signal - in simple terms - is just a bunch of 1s and 0s."

Yes I am aware of that, but digital TV cable providers can also provide broadband. Telewest is one example.

  keewaa 09:49 21 Feb 06

Now I understand your question. You're asking about cable broadband from the likes of NTL & Telewest which is different to adsl broadband from the likes of BT, Wanadoo etc. They don't use ordinary telephone lines, but special cable lines.

Unfortunately now I don't understand what the answer is as it is beyond me, hopefully there's an engineer here who will explain.

  Danoh 13:50 21 Feb 06

Wonderful to hear of your interest in learning about "how things work".

There are numerous articles on several web sites; would be a good idea for you to use Google to search for the terms you have mentioned. Certainly the topics involved are beyond the format of a forum's Q&A capability.

But I can't resist trying to do a synopsis, but only just for the one key point which I pick up in your 1st posting; "why use analogue when a PC uses only digital signals".

If a PC stays within a wired LAN connected only to other computers, they can communicate with each other and stay within the digital domain, as long as they use the same machine language (EDCIDIC/ASCII) and communication code (e,g. Novell, TCP/IP, etc).

But the wiring, networking kit and knowledge to do all of that is expensive; the larger the LAN with number of PCs and space to be covered, the more expensive it gets, in a non-linear fashion.

To be able to massively expand connectivity between computers (into what you refer to as the internet or WWW ~ World Wide WEB), the search for the largest, pre-existing wired network naturally settled on the telephone infrastructure.

But as you note, this is based on analogue signals. So the very first MoDems (Modulator/Demodulator) to transfer a digital signal to an analogue signal were actually acoustic! I remember having to stick an old-style BT phone receiver into rubber-cups on the top of a MoDem, so that sound would not escape.

MoDems moved to the pure electronic level when there was sufficient volumes sold. But they still did the same thing; modulated a digital signal on top of an existing carrier signal ~ at the other end, the analogue waveform is Demodulated back to digital for use by the PC.

Actually, a similar sort of thing happens with FAX machines. But that would be another story.

ADSL broadband actually uses the same copper pair as is used for analogue voice. The difference is that once you decide to move over to ADSL (or SDSL), that same copper pair no longer has an analogue carrier signal. It is moved over to the digital domain from your local exchange all the way to your PC. Which is why you need special "filters" to connect a standard analogue telephone to the same telephone wires/connectors, to demodulate the digital part of a voice call back into analogue which the phone can use.

Unless you are using VoIP; which is yet another story!!

Cable broadband stays purely in the digital domain, uses slightly different wiring (but not hugely so) and has a network separate to the established BT telephone network.

Hope that is a good introduction (only), into a wonderfully huge topic!!

P/S
I'm no longer an engineer, which is yet another story :-)

  Danoh 14:03 21 Feb 06

Like TV, satellites also used analogue signals in the past. However they have moved over to digital only. As TV is doing with Freeview.

Again, its a similar theory of using some carrier signal to carry information, which can be either analogue or digital. The transmission medium may change, but the principle is the same.

Be it down the old BT copper-pair, Cable wire, beamed from a Satellite, Microwave or TV Frequency band transmitter.

The differences are down to the detail of execution; be that for wired or wireless Ethernet, etc.

Better stop now!

This thread is now locked and can not be replied to.

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