Telephone's usable bandwidth?

[Tim Fisher]

What are the upper and lower limits of frequencies that can be
transmitted over the land-based telephone network to a standard home
handset?

What are the limiting components or design factors, and is there any
way to overcome this without additional hardware on the receiving end?

Thanks,

Tim

 

[John Tserkezis]

Tim Fisher wrote:

What are the upper and lower limits of frequencies that can be
transmitted over the land-based telephone network to a standard home
handset?

If I recall, 200Hz to 3.4Khz.

What are the limiting components or design factors,

Phone lines are no doubt better nowadays, but you don't know if you're going
through a pair gain, which would ultimatly reduce your available bandwidth.

and is there any
way to overcome this without additional hardware on the receiving end?

Not really. With compression hardware at both transmitting and recieving
ends, you may be able to squeeze more, but as is- you can't really trust more
than the official specs.

Depends on your application. If it's going to be widely used, you can only
really rely on the specs, if it's a one-off, you can test to see what you can
squeeze out of it, and use that as the 'typical'.

What are you trying to do? There may be other alternatives.

--
Linux Registered User # 302622 <http://counter.li.org>

 

[Roger Lascelles]

Here in Australia, phone lines were widely used by radio stations for live
broadcast events such as race calling. I know a guy who made the line
interface boxes used in Australia with microphone or line input. There
proved to be quite a lot more bandwidth available than advertised. I think
the lows went down sustantially. Things have changed now, since everything
gets converted to digital, but lines can produce much better sound than you
get through the telephone earpiece.

If you want to move non-audio, I suggest using a modem.

Roger

If I recall, 200Hz to 3.4Khz.

What are the limiting components or design factors,

Phone lines are no doubt better nowadays, but you don't know if you're
going
through a pair gain, which would ultimatly reduce your available
bandwidth.

and is there any
way to overcome this without additional hardware on the receiving end?

Not really. With compression hardware at both transmitting and
recieving
ends, you may be able to squeeze more, but as is- you can't really trust
more
than the official specs.

Depends on your application. If it's going to be widely used, you can
only
really rely on the specs, if it's a one-off, you can test to see what you
can
squeeze out of it, and use that as the 'typical'.

What are you trying to do? There may be other alternatives.

--
Linux Registered User # 302622
http://counter.li.org

 

[Roy McCammon]

Tim Fisher wrote:

What are the upper and lower limits of frequencies that can be
transmitted over the land-based telephone network to a standard home
handset?

What are the limiting components or design factors, and is there any
way to overcome this without additional hardware on the receiving end?

Thanks,

Tim

the handset itself rolls off around 4 KHz.
a digital central office rolls off very sharply
starting at about 3.3 KHz.

The wires themselves can support 1Mz or so for
short distances (circa 1 mile). Its more a s/n
ratio thing than a bw thing.

--
local optimization seldom leads to global optimization

my e-mail address is: <my first name> <my last name> AT mmm DOT com

 

[Tam/WB2TT]

Tim,

In this day and age, virtually all telephone company central office switches
are digital. That is, an incoming line is put through a nonlinear 8 bit A/D
converter that results in a 64 Kilobit/sec bit stream. This 64Kb/s is
multiplexed on to a ~32 Megabit/sec bit stream, and actual switching
consists of picking a particular 8 bit slot from this data. If you tried to
cheat by forcing a lot of energy down the line above 4 KHz, this energy
would come out the other end folded back to frequencies below 4 KHz. To get
more than <4 KHz bandwidth, you need to be hardwired at the CO to bypass the
normal switch,

Tam
"Tim Fisher" <tfisher2000@aol.com> wrote in message
news:bg4ma01f6jp20g5aclfmmma691td5j2qmp@4ax.com...

What are the upper and lower limits of frequencies that can be
transmitted over the land-based telephone network to a standard home
handset?

What are the limiting components or design factors, and is there any
way to overcome this without additional hardware on the receiving end?

Thanks,

Tim

 

[Paul Hovnanian P.E.]

Roy McCammon wrote:

Tim Fisher wrote:
What are the upper and lower limits of frequencies that can be
transmitted over the land-based telephone network to a standard home
handset?

What are the limiting components or design factors, and is there any
way to overcome this without additional hardware on the receiving end?

Thanks,

Tim

the handset itself rolls off around 4 KHz.
a digital central office rolls off very sharply
starting at about 3.3 KHz.

The wires themselves can support 1Mz or so for
short distances (circa 1 mile). Its more a s/n
ratio thing than a bw thing.

Right. It depends on what sort of circuit you order from the telco.
ISDN, DSL, and various other protocols use quite a bit of bandwidth.

But the OP asked about the capabilities of a 'standard home handset', so
I'm guessing that the application he has in mind can't rely upon the
existance of these services.

Another poster mentioned the use of telephone lines for high quality
audio broadcast feeds. Quite often, radio stations will arrange an ISDN
line from the telco for this purpose. Perhaps this is what was used to
obtain better audio quality.

--
Paul Hovnanian mailtoaul@Hovnanian.com
note to spammers: a Washington State resident
------------------------------------------------------------------
APL is a write-only language. I can write programs in APL, but I
can't read any of them.
-- Roy Keir

 

[MikeM]

Tim Fisher wrote:

What are the upper and lower limits of frequencies that can be
transmitted over the land-based telephone network to a standard home
handset?

What are the limiting components or design factors, and is there any
way to overcome this without additional hardware on the receiving end?

Thanks,

Tim

Back in the bad old days when there was a continuous copper twisted
pair between your house, to the Telco's central office, and finally to
a buddies house across town, you could get a lot more bandwidth than
just voice freqs. Now that the central offices are digital, then you
cant play these games anymore.

Computer modems attempt to take advantage of available bandwidth above
the voice frequencies. You can look at them as a "model" of data
rates that can be realized using the dial-up network.

MikeM

 

[Mike Page]

John Tserkezis wrote:

Tim Fisher wrote:

Phone lines are no doubt better nowadays, but you don't know if you're
going through a pair gain, which would ultimatly reduce your available
bandwidth.

Not so recently there was a report in the UK of an entire new housing
development unable to get ADSL because all lines tested failed the
checks. The reason was aluminium wire, it was too lossy. The new
occupiers were none too happy.


--
Mike Page BEng(Hons) MIEE www.eclectic-web.co.uk

 

[Bill Knight]

To get
more than <4 KHz bandwidth, you need to be hardwired at the CO to bypass the
normal switch,

Tam

And if it _were_ hardwired what would be the upper limit?

Another respondent mentioned 1MHz as the max the wiring would handle.

Also, what is the lowest frequency that can be delivered through the
handset coil, audible or not?

For example, will it do subaudio down to a few Hz and how much energy
could be dumped at this frequency?

Thanks,

Tim

 

[Reg Edwards]

Not so recently there was a report in the UK of an entire new housing
development unable to get ADSL because all lines tested failed the
checks. The reason was aluminium wire, it was too lossy

Mike Page BEng(Hons) MIEE

===========================

For a BEng(Hons) MIEE your technical education has been sadly neglected.

The difference in conductivity between copper and aluminium (a few percent)
is not enough to make any noticeable difference in data transmission.

The reason ADSL is not available is simply because subscribers are too far
from the the nearest telephone exchange.

And it is signal to noise and crosstalk ratios which set a limit to data
transmission.
---
Reg

 

[Tam/WB2TT]

"Bill Knight" <knightb@aol.com> wrote in message
news:qklna0l40u06hls6i907uu8v58pluq7m13@4ax.com...

To get
more than <4 KHz bandwidth, you need to be hardwired at the CO to bypass
the
normal switch,

Tam

And if it _were_ hardwired what would be the upper limit?

Another respondent mentioned 1MHz as the max the wiring would handle.

Also, what is the lowest frequency that can be delivered through the
handset coil, audible or not?

For example, will it do subaudio down to a few Hz and how much energy
could be dumped at this frequency?

Thanks,

Tim
At one time AT&T was considering transmitting (lousy) video over specially

equalized lines. BW was 100Hz to 1.1 MHz. Don't remember the signal power,
but it was somewhere around 0 dbm. T1 lines are essentially the same as
subscriber lines with all taps removed, and repeaters about every 4000 -
5000 feet. Signal amplitude at the source is around 6V peak.

Tam

 

[Tam/WB2TT]

"Reg Edwards" <g4fgq.regp@ZZZbtinternet.com> wrote in message
news:c8gmn9$ptt$1@hercules.btinternet.com...

Not so recently there was a report in the UK of an entire new housing
development unable to get ADSL because all lines tested failed the
checks. The reason was aluminium wire, it was too lossy

Mike Page BEng(Hons) MIEE

===========================

For a BEng(Hons) MIEE your technical education has been sadly neglected.

The difference in conductivity between copper and aluminium (a few
percent)
is not enough to make any noticeable difference in data transmission.

The reason ADSL is not available is simply because subscribers are too far
from the the nearest telephone exchange.

And it is signal to noise and crosstalk ratios which set a limit to data
transmission.
---
Reg


Reg,

It may be more insiduous than that. It is known that some European systems
use 32 KHz ADPCM encoding. Just what you need to connect 62 telephones to
the CO over 1 pair of wires using an E1 terminal. On a real good day, it
might connect at 9600. What this does, is to put 2 conversation on one
channel.

Tam

 

[Peter Bennett]

On Wed, 19 May 2004 07:59:06 -0700, "Paul Hovnanian P.E."
<Paul@Hovnanian.com> wrote:

Another poster mentioned the use of telephone lines for high quality
audio broadcast feeds. Quite often, radio stations will arrange an ISDN
line from the telco for this purpose. Perhaps this is what was used to
obtain better audio quality.

When I was in broadcasting (long before ISDN) we used "leased pairs"
from Telco - these were pairs in the Telco cables, but they didn't
pass through the Telco switching equipment. Instead, they went
through equalizing amplifiers in one or more central offices
(depending on distance and routing). The equalizers ensured that we
had broadcast-quality frequency response, but they also meant that
these were "one-way" cables. The equalized pair would only carry
audio from the remote location back to the studio. We had other,
non-equalized pairs, for talkback and other non-broadcast use.

--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

 

[Jan Panteltje]

On a sunny day (Wed, 19 May 2004 19:00:02 -0700) it happened Peter Bennett
<peterbb@somewhere.invalid> wrote in
<ps3oa0t7kvcf9va8ulmiqn4de33h5ilv1m@news.supernews.com>:

On Wed, 19 May 2004 07:59:06 -0700, "Paul Hovnanian P.E."
Paul@Hovnanian.com> wrote:


Another poster mentioned the use of telephone lines for high quality
audio broadcast feeds. Quite often, radio stations will arrange an ISDN
line from the telco for this purpose. Perhaps this is what was used to
obtain better audio quality.

When I was in broadcasting (long before ISDN) we used "leased pairs"
from Telco - these were pairs in the Telco cables, but they didn't
pass through the Telco switching equipment. Instead, they went
through equalizing amplifiers in one or more central offices
(depending on distance and routing). The equalizers ensured that we
had broadcast-quality frequency response, but they also meant that
these were "one-way" cables. The equalized pair would only carry
audio from the remote location back to the studio. We had other,
non-equalized pairs, for talkback and other non-broadcast use.
Yes, I remember this, these were called 'music lines' over here.

Anytime some progam came from any where in the country we got those
lines, I have measured countless frequency responses on those lines
(every time before program start), and that was in the 60ties, and
really I can't remember the max freq.
I remember 10kHz, maybe also 15 kHz?
Good old days
Also we used these lines for international news exchange via Brussels
EBU.
These lines were measured every day, for distortion, and frequency
response.
And we had an intercom / conference line from all european broadcasters
with EBU Brussels for just that sort of thing.
Presume it is all digital now.
JP

 

[Mike Page]

Reg Edwards wrote:

Not so recently there was a report in the UK of an entire new housing
development unable to get ADSL because all lines tested failed the
checks. The reason was aluminium wire, it was too lossy

Mike Page BEng(Hons) MIEE


===========================

For a BEng(Hons) MIEE your technical education has been sadly neglected.

The difference in conductivity between copper and aluminium (a few percent)
is not enough to make any noticeable difference in data transmission.

In its elemental form aluminium is 58% more resistive than copper, and
the common alloys are up to 200% more resistive.

Here's an interesting link http://www.dubery.co.uk/adrox/technical.htm


Cheers,
Mike.

--
Mike Page BEng(Hons) MIEE www.eclectic-web.co.uk

 

[Richard Henry]

"Mike Page" <mike@SCRUBeclectic-CAPSweb.BLAMEco.SWENuk> wrote in message
news:1085075484.968627@news01.eclipse.net.uk...

Reg Edwards wrote:
Not so recently there was a report in the UK of an entire new housing
development unable to get ADSL because all lines tested failed the
checks. The reason was aluminium wire, it was too lossy

Mike Page BEng(Hons) MIEE


===========================

For a BEng(Hons) MIEE your technical education has been sadly neglected.

The difference in conductivity between copper and aluminium (a few
percent)
is not enough to make any noticeable difference in data transmission.

In its elemental form aluminium is 58% more resistive than copper, and
the common alloys are up to 200% more resistive.

Here's an interesting link http://www.dubery.co.uk/adrox/technical.htm

In my two summers (66 and 67) working as an electrician, the boss always
gave the customer the choice between copper and aluminum wiring. The smart
ones paid more for the copper.

 

[Le Chaud Lapin]

Roy McCammon <rbmccammon@mmm.com> wrote in message news:<40AB6767.6020201@mmm.com>...

the handset itself rolls off around 4 KHz.
a digital central office rolls off very sharply
starting at about 3.3 KHz.

The wires themselves can support 1Mz or so for
short distances (circa 1 mile). Its more a s/n
ratio thing than a bw thing.

It is also important to mention what part of the "telephone" is meant.

If it is the wire from the telephone unit to the face plate, that
would not be the same as for the cat-3 wire inside the house, where
you can actually get ethernet speeds under certain circumstances. (I
once got almost 1Mb/s by butchering some cat-3 cable tied in with
Coax). If you mean the wire from the house's point of demarcation to
central office, assuming local loop length of over 20,000 ft, you can
expect DSL to attempt to use the entire 1.1MHz, starting at 4KHz,
using quadrature or other techniques to maximize spectral efficiency.

Perhaps one should ask what is the maximum expected bit rate from
demarcation to CO since it is quite possible to use frequencies well
beyond 1.1MHz if one is willing to tolerate a corresponding reduction
in througput and symbol delay.

-Chaud Lapin-

 

[Reg Edwards]

In its elemental form aluminium is 58% more resistive than copper, and
the common alloys are up to 200% more resistive.
=================================

Aluminium alloys are used for ladders, jewellry, etc. Near pure aluminium
wire is always used in phone lines. At data frequencies it has a resistance
about 30 percent greater than copper. But to maintain a standard loss per
mile of cable it has a greater wire diameter. It is not used so much in
phone lines because of its mechanical properties when jointing and when
connected to copper. It cannot be soldered.

================================

The international standard for the last 70 years for phone-line speech
circuits has a band spacing of 4.00 KHz which also accommodates signalling
frequency requirements. When in a standard condition the typical frequency
band occupied by speech between a pair of subscribers is fairly flat between
300 Hz and 3.2 KHz and may extend from 200 Hz to 3.6 KHz.

Between subscribers on the same exchange the frequency response may be
limited by the response of the microphone and the earpiece which is variable
and pretty poor.
----
Reg.

 

[Tam/WB2TT]

"Le Chaud Lapin" <unoriginal_username@yahoo.com> wrote in message
news:fc2e0ade.0405201357.2dcd5617@posting.google.com...

Roy McCammon <rbmccammon@mmm.com> wrote in message
news:<40AB6767.6020201@mmm.com>...

the handset itself rolls off around 4 KHz.
a digital central office rolls off very sharply
starting at about 3.3 KHz.

The wires themselves can support 1Mz or so for
short distances (circa 1 mile). Its more a s/n
ratio thing than a bw thing.

It is also important to mention what part of the "telephone" is meant.

If it is the wire from the telephone unit to the face plate, that
would not be the same as for the cat-3 wire inside the house, where
you can actually get ethernet speeds under certain circumstances. (I
once got almost 1Mb/s by butchering some cat-3 cable tied in with
Coax). If you mean the wire from the house's point of demarcation to
central office, assuming local loop length of over 20,000 ft, you can
expect DSL to attempt to use the entire 1.1MHz, starting at 4KHz,
using quadrature or other techniques to maximize spectral efficiency.

Perhaps one should ask what is the maximum expected bit rate from
demarcation to CO since it is quite possible to use frequencies well
beyond 1.1MHz if one is willing to tolerate a corresponding reduction
in througput and symbol delay.

-Chaud Lapin-

This all assumes you have a metallic connection to the CO.

Tam

 

[Mike Page]

Reg Edwards wrote:

In its elemental form aluminium is 58% more resistive than copper, and
the common alloys are up to 200% more resistive.

=================================

Aluminium alloys are used for ladders, jewellry, etc. Near pure aluminium
wire is always used in phone lines. At data frequencies it has a resistance
about 30 percent greater than copper.

Please elaborate.


--
Mike Page BEng(Hons) MIEE www.eclectic-web.co.uk