Increasing the speed of dial-up to that of cable -- possible?

"Floyd L. Davidson" wrote:
CBFalconer wrote:

.... snip ...

Your 'no 4000 Hz' no doubt refers to the signalling reservation.

No, 4000 Hz has nothing to do with signaling. It is
*IMPOSSIBLE*, both in theory and in practice, to pass
4000 Hz through a single channel over the switched PSTN.

In the good old days 4000 hz was reserved for signalling blasts
over the analog lines, and there were dire retributions due for
anyone who had the temerity to introduce 4kHz onto the lines.
There is no such thing as an analog filter with infinite cut-off.

--
Chuck F (cbfalconer at maineline dot net)
Available for consulting/temporary embedded and systems.
http://cbfalconer.home.att.net



--
Posted via a free Usenet account from http://www.teranews.com

On Fri, 17 Aug 2007 05:00:11 -0800, (Floyd L. Davidson)
wrote:

Actually the POTS network is designed to carry roughly 300-4000 Hz

More like 400-2800 Hz,

In Europe 300-3400Hz is the standard.

CBFalconer wrote:
"Floyd L. Davidson" wrote:
CBFalconer wrote:

... snip ...

Your 'no 4000 Hz' no doubt refers to the signalling reservation.

No, 4000 Hz has nothing to do with signaling. It is
*IMPOSSIBLE*, both in theory and in practice, to pass
4000 Hz through a single channel over the switched PSTN.

In the good old days 4000 hz was reserved for signalling blasts
over the analog lines,

That isn't true.

Nobody has *ever* used 4000 Hz for signaling. Let me
give you a clue: You cannot, and have *never* been able
to, pass 4000Hz over any carrier system used for the
PSTN.

The closest thing to that were the Lenkurt analog FDM
systems (such as 45BX carrier) that use "out of band
signaling", at 3700 Hz (the US standard, while CCITT
specified 3825 Hz). In fact, any signaling tones above
3400 Hz are considered "out of band".

and there were dire retributions due for
anyone who had the temerity to introduce 4kHz onto the lines.

Indeed, there *are* (as in there are still the exact same
reasons, and it is forbidden). It has nothing to do with
signaling.

There is no such thing as an analog filter with infinite cut-off.

What's your point though?

There *are* some rather good analog filters. In fact
the way that ADSL works, putting data on top of you
voice line, is by using frequencies above 4000 Hz and
filters. It is the _customer_ that is not allowed to put
anything above 4000 Hz on a POTS loop.

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

Ken wrote:
On Fri, 17 Aug 2007 05:00:11 -0800, (Floyd L. Davidson)
wrote:

Actually the POTS network is designed to carry roughly 300-4000 Hz

More like 400-2800 Hz,

In Europe 300-3400Hz is the standard.

If you check that out, you'll find it isn't. A POTS
connection is only guaranteed to pass 400-2800 Hz. That
is the minimum specification.

Not that individual channels (and even circuits) are
never specified at 300-3400 Hz, because they are.

But if you measure a POTS line and find that nothing above
3000 Hz gets through, it will not mean the line is out of
specs.

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)