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Paul Ingram
Guest
Thu Mar 04, 2010 6:02 am
Does anyone know what are the highest and lowest frequencies that can
be transmitted as CW over a commercial wired telephone network?
Could bypassing the mic and speaker extend this range?
Paul Ingram
krw@att.bizzzzzzzzzzzz
Guest
Thu Mar 04, 2010 6:10 am
On Thu, 04 Mar 2010 05:02:30 GMT, paulingram_at_oslotec.com (Paul Ingram) wrote:
Quote:
Does anyone know what are the highest and lowest frequencies that can
be transmitted as CW over a commercial wired telephone network?
POTS is limited at the upper end by the DACs. They use 8k samples per second,
so that's ideally a 4kHz bandwidth. I'm not sure what the low end limiter is,
but it's supposed the spec is 300Hz.
Quote:
Could bypassing the mic and speaker extend this range?
No.
FatBytestard
Guest
Thu Mar 04, 2010 6:47 am
On Thu, 04 Mar 2010 05:02:30 GMT, paulingram_at_oslotec.com (Paul Ingram)
wrote:
Quote:
Does anyone know what are the highest and lowest frequencies that can
be transmitted as CW over a commercial wired telephone network?
Could bypassing the mic and speaker extend this range?
Paul Ingram
Ask Floyd L. Davidson up in alt.engineering.electrical
Jon Kirwan
Guest
Thu Mar 04, 2010 7:05 am
On Wed, 03 Mar 2010 23:10:18 -0600, "krw_at_att.bizzzzzzzzzzzz"
<krw_at_att.bizzzzzzzzzzzz> wrote:
Quote:
On Thu, 04 Mar 2010 05:02:30 GMT, paulingram_at_oslotec.com (Paul Ingram) wrote:
Does anyone know what are the highest and lowest frequencies that can
be transmitted as CW over a commercial wired telephone network?
POTS is limited at the upper end by the DACs. They use 8k samples per second,
so that's ideally a 4kHz bandwidth. I'm not sure what the low end limiter is,
but it's supposed the spec is 300Hz.
snip
Bandwidth is specified as 300Hz - 3000Hz. 2700Hz width. Not
4k. They may provide more, but my more recent tests suggest
they hard limit it pretty close these days. Back when
(1950's), it was much more.
I've got a copy of the official specifications on the shelf,
if anyone needs specific citations. They are designed to
cover different phone and switching systems, but they all
agree on this point.
There was a ruckus some years after when tape players made it
into business places after WW II (german invention discovered
in captured tanks, I think) where some folks would tape at
normal speed and play fast for international calls to short
the time (and expense), allowing the other side to record
fast and then play back slower. I think that was part of the
first "why" that AT&T started figuring it was worth some
trouble to start sticking low pass filters in the line.
That's the story I heard and I'm sticking to it. But I have
no real idea, at all. Sounded good when I heard it, maybe 30
years back, though.
Anyway, the easiest way to tell is just sit at a piano, hit
keys, and let the other side tell you when it goes "clunk,
clunk" instead of a nice tone.
Jon
John Larkin
Guest
Thu Mar 04, 2010 7:23 am
On Wed, 03 Mar 2010 22:05:18 -0800, Jon Kirwan
<jonk_at_infinitefactors.org> wrote:
Quote:
On Wed, 03 Mar 2010 23:10:18 -0600, "krw_at_att.bizzzzzzzzzzzz"
krw_at_att.bizzzzzzzzzzzz> wrote:
On Thu, 04 Mar 2010 05:02:30 GMT, paulingram_at_oslotec.com (Paul Ingram) wrote:
Does anyone know what are the highest and lowest frequencies that can
be transmitted as CW over a commercial wired telephone network?
POTS is limited at the upper end by the DACs. They use 8k samples per second,
so that's ideally a 4kHz bandwidth. I'm not sure what the low end limiter is,
but it's supposed the spec is 300Hz.
snip
Bandwidth is specified as 300Hz - 3000Hz. 2700Hz width. Not
4k. They may provide more, but my more recent tests suggest
they hard limit it pretty close these days. Back when
(1950's), it was much more.
I've got a copy of the official specifications on the shelf,
if anyone needs specific citations. They are designed to
cover different phone and switching systems, but they all
agree on this point.
There was a ruckus some years after when tape players made it
into business places after WW II (german invention discovered
in captured tanks, I think) where some folks would tape at
normal speed and play fast for international calls to short
the time (and expense), allowing the other side to record
fast and then play back slower. I think that was part of the
first "why" that AT&T started figuring it was worth some
trouble to start sticking low pass filters in the line.
That's the story I heard and I'm sticking to it. But I have
no real idea, at all. Sounded good when I heard it, maybe 30
years back, though.
Anyway, the easiest way to tell is just sit at a piano, hit
keys, and let the other side tell you when it goes "clunk,
clunk" instead of a nice tone.
Jon
Originally one pair of wires sent one long-distance call. Then, to
save wire, a bunch of calls were sent SSB over one pair, over
close-spaced carriers. The Western Electric "J" system used 4 KHz
channel spacings, so the baseband audio was sharply filtered between
300 and 2600 Hz to avoid channel-channel crosstalk.
Later digital systems sampled at 8 KHz, so an antialiasing filter
preceded the digitizer, usually about 2700 Hz.
The tape recorder thing doesn't make much sense. International phone
lines never had enough bandwidth to allow that trick.
John
Jon Kirwan
Guest
Thu Mar 04, 2010 9:15 am
On Wed, 03 Mar 2010 22:23:22 -0800, John Larkin
<jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
Quote:
On Wed, 03 Mar 2010 22:05:18 -0800, Jon Kirwan
jonk_at_infinitefactors.org> wrote:
On Wed, 03 Mar 2010 23:10:18 -0600, "krw_at_att.bizzzzzzzzzzzz"
krw_at_att.bizzzzzzzzzzzz> wrote:
On Thu, 04 Mar 2010 05:02:30 GMT, paulingram_at_oslotec.com (Paul Ingram) wrote:
Does anyone know what are the highest and lowest frequencies that can
be transmitted as CW over a commercial wired telephone network?
POTS is limited at the upper end by the DACs. They use 8k samples per second,
so that's ideally a 4kHz bandwidth. I'm not sure what the low end limiter is,
but it's supposed the spec is 300Hz.
snip
Bandwidth is specified as 300Hz - 3000Hz. 2700Hz width. Not
4k. They may provide more, but my more recent tests suggest
they hard limit it pretty close these days. Back when
(1950's), it was much more.
I've got a copy of the official specifications on the shelf,
if anyone needs specific citations. They are designed to
cover different phone and switching systems, but they all
agree on this point.
There was a ruckus some years after when tape players made it
into business places after WW II (german invention discovered
in captured tanks, I think) where some folks would tape at
normal speed and play fast for international calls to short
the time (and expense), allowing the other side to record
fast and then play back slower. I think that was part of the
first "why" that AT&T started figuring it was worth some
trouble to start sticking low pass filters in the line.
That's the story I heard and I'm sticking to it. But I have
no real idea, at all. Sounded good when I heard it, maybe 30
years back, though.
Anyway, the easiest way to tell is just sit at a piano, hit
keys, and let the other side tell you when it goes "clunk,
clunk" instead of a nice tone.
Jon
Originally one pair of wires sent one long-distance call. Then, to
save wire, a bunch of calls were sent SSB over one pair, over
close-spaced carriers. The Western Electric "J" system used 4 KHz
channel spacings, so the baseband audio was sharply filtered between
300 and 2600 Hz to avoid channel-channel crosstalk.
There remains the tariffs for POTS which state 300Hz to
3000Hz as the required bandpass. I believe I must have read
them more than a few times, by now.
Quote:
Later digital systems sampled at 8 KHz, so an antialiasing filter
preceded the digitizer, usually about 2700 Hz.
The tape recorder thing doesn't make much sense. International phone
lines never had enough bandwidth to allow that trick.
It was one of those tales I heard from someone working at the
phone company, back then. I frankly had (and have) no idea.
Jon
Robert Baer
Guest
Thu Mar 04, 2010 9:52 am
Paul Ingram wrote:
Quote:
Does anyone know what are the highest and lowest frequencies that can
be transmitted as CW over a commercial wired telephone network?
Could bypassing the mic and speaker extend this range?
Paul Ingram
I think the bandwidth is supposed to be 3KHz, but do mot know if that
is the 3dB point and do not know the rolloff rate.
However, traditionally (ie up to 5 years ago and maybe later) one
could *reliably* get 48Kbaud data rate with a modem.
But (some??) telcos have deliberately, in some unknown manner,
throttled that so the best one can now do is 28.8Kbaud.
And the response from then as well as from PUCs is "all we are
required to support is VOICE QUALITY".
BARF!
AFAIK there is not a goddamn thing anyone can do about that.
I say it will get worse as the greed of telcos will allow them to
decrease that to maybe a max of 1Kbaud.
Why? so that dial-up "customers" will get so fed up with slow
internst that they will pay $$$ for "high speed" (which seems to never
be as fast as advertised - and definitely not as reliable as dial-p).
Robert Baer
Guest
Thu Mar 04, 2010 9:54 am
krw_at_att.bizzzzzzzzzzzz wrote:
Quote:
On Thu, 04 Mar 2010 05:02:30 GMT, paulingram_at_oslotec.com (Paul Ingram) wrote:
Does anyone know what are the highest and lowest frequencies that can
be transmitted as CW over a commercial wired telephone network?
POTS is limited at the upper end by the DACs. They use 8k samples per second,
so that's ideally a 4kHz bandwidth. I'm not sure what the low end limiter is,
but it's supposed the spec is 300Hz.
Could bypassing the mic and speaker extend this range?
No.
Please comment as to WTF telcos did to throttle dial-up from 48Kbaud
to 28.8Kbaud.
oopere
Guest
Thu Mar 04, 2010 11:15 am
Paul Ingram wrote:
Quote:
Does anyone know what are the highest and lowest frequencies that can
be transmitted as CW over a commercial wired telephone network?
Could bypassing the mic and speaker extend this range?
Paul Ingram
"The" telephone channel is usually specified as 300..3400 Hz. This is
what is guaranteed to be transmitted to anywhere on the world. The
bandwidth of the transmission line between you and the first electronic
gadget it meets is from dc to something that is specific to each case.
Pere
Jim Yanik
Guest
Thu Mar 04, 2010 1:39 pm
Robert Baer <robertbaer_at_localnet.com> wrote in news:-
aSdnakxDbTj6RLWnZ2dnUVZ_o-dnZ2d_at_posted.localnet:
Quote:
Paul Ingram wrote:
Does anyone know what are the highest and lowest frequencies that can
be transmitted as CW over a commercial wired telephone network?
Could bypassing the mic and speaker extend this range?
Paul Ingram
I think the bandwidth is supposed to be 3KHz, but do mot know if that
is the 3dB point and do not know the rolloff rate.
However, traditionally (ie up to 5 years ago and maybe later) one
could *reliably* get 48Kbaud data rate with a modem.
I'm still on dialup,and I usually log on at 48K,according to the W98SE
taskbar indicator.Sometimes,it logs on at 49K,but it's never stable.
ISTR that the max limit was 52K,but was usually limited by coils in the
lines.
Century Link in central Florida is my telco.
--
Jim Yanik
jyanik
at
localnet
dot com
MakeNoAttemptToAdjustYour
Guest
Thu Mar 04, 2010 2:14 pm
On Thu, 04 Mar 2010 06:39:17 -0600, Jim Yanik <jyanik_at_abuse.gov> wrote:
Quote:
Robert Baer <robertbaer_at_localnet.com> wrote in news:-
aSdnakxDbTj6RLWnZ2dnUVZ_o-dnZ2d_at_posted.localnet:
Paul Ingram wrote:
Does anyone know what are the highest and lowest frequencies that can
be transmitted as CW over a commercial wired telephone network?
Could bypassing the mic and speaker extend this range?
Paul Ingram
I think the bandwidth is supposed to be 3KHz, but do mot know if that
is the 3dB point and do not know the rolloff rate.
However, traditionally (ie up to 5 years ago and maybe later) one
could *reliably* get 48Kbaud data rate with a modem.
I'm still on dialup,and I usually log on at 48K,according to the W98SE
taskbar indicator.Sometimes,it logs on at 49K,but it's never stable.
ISTR that the max limit was 52K,but was usually limited by coils in the
lines.
Century Link in central Florida is my telco.
NO. NONE of you get those speeds. Those speeds are IF the handshake
can pipe multiple streams into your NOISE FREE line. The line is NEVER
noise free, and the actual hardware speed is NEVER more than 32k bits/per
second, and even that is derived from stacking several 9600 baud streams
together and that only happens on the best, most noise free connections,
which are closest to their switch.
It is limited by the integrity of the link between you and your first
digital switch point, which is usually not all that great.
AZ Nomad
Guest
Thu Mar 04, 2010 2:28 pm
On Thu, 04 Mar 2010 05:02:30 GMT, Paul Ingram <paulingram_at_oslotec.com> wrote:
Quote:
Does anyone know what are the highest and lowest frequencies that can
be transmitted as CW over a commercial wired telephone network?
jfgi
JW
Guest
Thu Mar 04, 2010 3:41 pm
On Thu, 04 Mar 2010 07:28:15 -0600 AZ Nomad
<aznomad.3_at_PremoveOBthisOX.COM> wrote in Message id:
<slrnhovdbf.jaj.aznomad.3_at_ip70-176-155-130.ph.ph.cox.net>:
Quote:
On Thu, 04 Mar 2010 05:02:30 GMT, Paul Ingram <paulingram_at_oslotec.com> wrote:
Does anyone know what are the highest and lowest frequencies that can
be transmitted as CW over a commercial wired telephone network?
jfgi
Or:
http://www.justfuckinggoogleit.com/
Martin Brown
Guest
Thu Mar 04, 2010 3:48 pm
osr_at_uakron.edu wrote:
Quote:
On Mar 4, 3:54 am, Robert Baer <robertb...@localnet.com> wrote:
k...@att.bizzzzzzzzzzzz wrote:
On Thu, 04 Mar 2010 05:02:30 GMT, pauling...@oslotec.com (Paul Ingram) wrote:
Does anyone know what are the highest and lowest frequencies that can
be transmitted as CW over a commercial wired telephone network?
POTS is limited at the upper end by the DACs. They use 8k samples per second,
so that's ideally a 4kHz bandwidth. I'm not sure what the low end limiter is,
but it's supposed the spec is 300Hz.
Could bypassing the mic and speaker extend this range?
No.
Please comment as to WTF telcos did to throttle dial-up from 48Kbaud
to 28.8Kbaud.
Google "concentrator" a widget that pipes more lines down existing
copper pairs..
In the UK they call them DACS. Ugly prehistoric technology devices that
totally destroy bandwidth to share one real copper line. eg
http://frank.gwc.org.uk/~ali/dacs/
There used to be a site with a spectrum analyser on that could be dialed
into on a modem and would return a 3 bands per octave spectrum.
Quote:
My beef is that cell uses so much compression, you cant use a modem
with cell.
OTOH you can use cellular for bulk datastreams and get reasonable price
performance for modest amounts of data. No good for video on demand but
fine for Usenet and casual web browsing.
Quote:
And I'm stuck in a area with no wimax, so its $$$$ cable or death,
because the previous idiot renter of the apartment signed a paper
allowing removal of the copper pair...
Can't you get the telco to give you a real copper wire and pinch it off
some old dear who just has a basic handset? That is what they do round
here when the real copper is running out. Applying for an ADSL service
from your supplier should get you out of the speed rut.
Regards,
Martin Brown
Vladimir Vassilevsky
Guest
Thu Mar 04, 2010 3:56 pm
John Larkin wrote:
Quote:
Originally one pair of wires sent one long-distance call. Then, to
save wire, a bunch of calls were sent SSB over one pair, over
close-spaced carriers. The Western Electric "J" system used 4 KHz
channel spacings, so the baseband audio was sharply filtered between
300 and 2600 Hz to avoid channel-channel crosstalk.
2.6kHz bandlimiting significantly deteriorates the clarity of speech.
Quote:
Later digital systems sampled at 8 KHz, so an antialiasing filter
preceded the digitizer, usually about 2700 Hz.
????
3.6 kHz that is.
There was an initiative for 16kHz sampling utilizing the same 56/64kbps
carrier bandwidth (G.722 and such). That makes the quality significantly
better; however it didn't receive wide acceptance.
Quote:
The tape recorder thing doesn't make much sense. International phone
lines never had enough bandwidth to allow that trick.
The tape recoder idea originates from spy novels.
Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
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