🚀 go-pugleaf

In article <344BC367.16F690F0@looking-glass.org>
           bnb-877985178@news.looking-glass.org "Brian Blackmore" writes:

> Robert Sneddon wrote:
> > 
> >  I think many of the people involved in this discussion are missing
> > a major point :
> > 
> >  A modem-to-modem connection is analog, not digital.
> 
> I may be wrong, but this is no longer always the case, in particular it
> is *not* the case with a 56k modem.
> 
> A connection to an ISP is in general an analog <--> digital connection,
> the "modem" at the ISP's end being a direct digital connection to the
> telephony network.
> 
> A 56k modem works by relying upon the fact that the telephony network is
> in fact digital, thus rather than whistling down the network (as a
> traditional modem does) it sends distinct symbols,

 Symbols? Are they represented by digital voltage changes (on-off), or by
varying tones with varying phase-shifts? If the latter, the same problems
will occur. The increasing intelligence inside the modem means it can
discriminate between line noise and signal better than before, and hence
the rising modem speeds we have seen over the last 10-15 years. Remember
the Prestel 1200/75 baud modems? There will still be instances when
Snap, Crackle and Pop will do for the link, and Demon will be blamed.

> and so long as the 
> connection remains on a digital network no transmission loss will occur.

 Agreed.

> The problem of course occurs when the connection leaves the concentrator
> and travels down the subscribers line as an analog signal

 This is where 99% of the dodgy modem connections occur, causing the data
rate drops (and in the worst cases, line drops). Remember, even a voice
telephone call is digital between exchanges. An ISP, especially like
Demon, is effectively an exchange on the digital trunks.

 To use an (bad) analogy, there are a lot of B-roads that connect where
I live to the motorway nearby. They are full of pot-holes, sharp bends
and the occasional farm animal. My maximum speed on my trip will be 70mph,
but my average will be a lot less. I might even smash a wheel in one of
those potholes, or hit a sheep, or... and so I might not complete my
journey. To strain the analogy even further, Demon is a motorway service
area, with hardly any "minor" roads between it and the motorway. An
ISDN link is sitting on a motorway slip road. The 56k modems are
Ferraris which have still to negotiate the potholes, farm animals etc.
on the twisty little B-roads. Some days the road is clear, and some days
it's market day, and the road is covered in cow extrusions...

 Demon are still going to be for a hammering as the 56k modem buyers
discover that their precious box of electronicals can't actually deliver
56,000 bits per second because it wasn't designed to work on British
telecomms systems, but on American equipment. I wish the help desk
people rotsa ruck. 

 Roll on subscriber fibre, that's what I say...

-- 
 To reply via email, remove the string "_nospam_" from my address.

Robert (nojay) Sneddon