Why do you connect to an ADSL line with a Modem?

  wee eddie 15:30 12 Jan 2006
Locked

a Modulator - Demodulator.

Which converts the PC's digital signal to an Analogue Signal for the purpose of the Phone line.

Where-as ADSL is all Digital!

I think.

Or do we call it a Modem because this has become the Generic term?

  Skyver 15:48 12 Jan 2006
  wee eddie 16:18 12 Jan 2006

an ADSL Modem is no longer a Modulator-Demodulator as the signal is transmitted in a different form.

Modem has become the generic term for the transmitting device needed to push & receive the Internet's signal.

  dms05 14:26 16 Jan 2006

The approach an ADSL modem takes is very simple in principle. The phone line's bandwidth between 24,000 hertz and 1,100,000 hertz is divided into 4,000-hertz bands, and a virtual modem is assigned to each band. Each of these 249 virtual modems tests its band and does the best it can with the slice of bandwidth it is allocated. The aggregate of the 249 virtual modems is the total speed of the pipe.

  jack 14:48 16 Jan 2006

How does this equate with this puzzle?
I have a mildy disabled daughte - She's OK lives alone and copes pretty well but certain things need helping out on.
I was looking at her phone bill and noticed her BT package was different and no Internet phone calls logged.
So I sked whats this then?
She said a BT man offered her special deal and it looked good so she said OK.
She then said 'I also got this' rummaging under her desk. 'But I could not get it do do anything so I unplugged it'and where upon dragged out a BT/Yahoo broad band box with all the bits.
I have yet to take a deeper look but it seems to infer she is on a BB link but using plain vanilla 56k modem - a puzzle or what?

  DieSse 15:55 16 Jan 2006

*I have yet to take a deeper look but it seems to infer she is on a BB link but using plain vanilla 56k modem - a puzzle or what?*

A BB link is only a phone line - so a dial-up modem will work on it as normal. To work well you would normally need to use a micro-filter, but I have seen them working without when the BB modem is disconnected.

  Forum Editor 16:02 16 Jan 2006

The dialup modem will obviously only work on the analogue part of the line - it won't connect to the broadband service. In fact, I'm surprised it works at all if it's connected without a microfilter - there's normally far too much line noise.

You'll be able to tell if your daughter signed up for a broadband service, because she'll have a direct debit set up on her bank account. It's most odd if no call charges are accruing in her phone bill though - I should investigate that before your daughter gets a nasty surprise in the post one day.

  DieSse 16:04 16 Jan 2006

*Modem has become the generic term for the transmitting device needed to push & receive the Internet's signal.*

No it hasn't - an ISDN line (which is a true digital line) is run from an ISDN Adapter - they aren't called modems.

ADSL uses in-line adaptive modulation - ergo it can be called a modem.

  Forum Editor 16:14 16 Jan 2006

What wee eddie said is perfectly correct.

D-Link, 3-Com, and various other manufacturers refer to their ISDN adapters as 'modems' - as do many people in the IT industry. It's just far simpler to do so, and everyone knows what's meant.It's a generic term, as wee eddie said - let's not get trapped in the semantics, for goodness sake.

  wee eddie 16:29 16 Jan 2006

Thank you very much for reading my question.

As you will know, my knowledge of the subject is limited and this anachronism was bugging me.

You have cleared it up and I'm happy.

I shall happily carry on Hoovering with my Dyson!

  DieSse 16:33 16 Jan 2006

The question the thread was based on was about semantics - that's why I explained the difference.

Most of the time, most manufacturers do refer to ISDN products correctly as Terminal Adapters.

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

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