Hum from phone wires running next to mains?

[Floyd L. Davidson]

Foxtrot <foxtrot@demo.invalid> wrote:

On Tue 04 Mar 2008 21:22:30, <phil-news-nospam@ipal.net> wrote:
That twist is a great little means to ensure induced signals,
whatever they may be, are induced in equal amount on both wires, so
they do not contribute to the actual intended signal that is a
differential between those two wires.

However, a risk exists when two different pairs are present next to
each other and each pair is twisted at the same pitch. The signal
carried by one can end up being induced differentially on the
other. So don't twist those power lines, or if you do, twist them
at a pitch with a ratio to the phone line twist that is not a whole
number.

Twist the power lines all you like. You *can't*
physically twist them identically to that of a comm
cable *and* get the two pairs to snuggle up to each
other in a way that will create the problem described
above.

Regardless, it isn't "smart" to run a comm cable in
physical contact with power cabling. Even a couple of
inches separation is sufficient to significantly reduce
common mode coupling. And the fact that no hum is heard
when it is first installed is *not* sufficient reason to
accept such practice. The common mode voltage induced
on the comm cable may not be a problem at any given
time, but it means that in the future anything (such as
kinks in the cable, dampness, damaged insulation, etc)
that reduces the balance *will* cause excessive hum.
The higher the common mode induced voltage, the less
unbalance required to cause objectionable hum.

If you can avoid putting the two types of cable
together, you *should*.

CAT5 cable is an example. It has 4 different pairs twisting along.
Each of the pairs has a different twist pitch by design (unless
you get some cheap cable not manufactured correctly).

All multipair twisted-pair cable uses different twists
for each pair. That is identically true for bundled
pairs in telephone cable. Moreover, if there are
multiple bundles the bundles are swirled within the
jacket too.

I do not have any technical knowledge of this area.

I would like to ask about a cable which has two or more twisted pairs
in it.

Is there is a greaterlikelihood of hum if I connect a "2 wire" phone
extension by using one wire from a twisted pair and taking the second
wire from a different twisted pair?

That is referred to as a "split pair", and yes it will
cause problems. It commonly happens with CAT5 cabling
due to the different standards for pin assignments for a
DS1 interface and for 10BaseT Ethernet. Typically a DS1
cable will work for Ethernet if the length is short, but
if used for faster than 10baseT, it won't work at all,
even for a 6 foot jumper cable.

On large telephone cables split pairs invariably have
significant crosstalk (either hum or speech from other
cables).

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

 

[Ivor Jones]

"Foxtrot" <foxtrot@demo.invalid> wrote in message
news:Xns9A57F1761E171D712E3@127.0.0.1

[snip]

: : I do not have any technical knowledge of this area.
: :
: : I would like to ask about a cable which has two or more
: : twisted pairs in it.
: :
: : Is there is a greaterlikelihood of hum if I connect a
: : "2 wire" phone extension by using one wire from a
: : twisted pair and taking the second wire from a
: : different twisted pair?

Why would you want to do that..? The answer is very probably, so ensure
that the pair of wires you use are twisted *together*..!

Ivor

 

[Foxtrot]

On Tue 04 Mar 2008 19:13:07, Graham. <me@privacy.com> wrote:

"Foxtrot" <foxtrot@demo.invalid> wrote in message
news:Xns9A57AA15ACE8ED712E3@127.0.0.1...
I am in the UK and want to make several phone extensions.

QUESTION: I would like to know I this will increase the level of
hum.

ISTR UK phones have a transformer and some other components to
neutralise hum but would that be good enough to prevent hum from a
messy setup like mine? Some details are below.

-------------------------

In my situation the phone extension wires and the mains wires will
run close to one other.

There will be about four or five additional extension phone
sockets.

And in some phone sockets there will be a loose extension lead of
approx 3 metres which will be almost ontop of curled mains flex


It is quite difficult to induce hum into telephone wiring.
Use twisted pair cabling rather than the flat ready-made
extension cables.

(As you suggest, I will not get the flat ready made extension cable
which I guess is made from flexible multi-stranded wires.)

Is the sort of cable sold in the UK specifically for domestic
telephone wall sockets (wuth single stranded wires) usually made up
as "twisted pair" in the way you are recommending?

 

[Foxtrot]

On Tue 04 Mar 2008 21:22:30, <phil-news-nospam@ipal.net> wrote:

In alt.engineering.electrical gfretwell@aol.com wrote:
| On Tue, 4 Mar 2008 19:13:07 -0000, "Graham." <me@privacy.com
| wrote:

|>It is quite difficult to induce hum into telephone wiring.
|>Use twisted pair cabling rather than the flat ready-made
|>extension cables.
|
| Exactly!
| The phone company has millions of miles of cable running right
| below power lines and hundreds literally touching each other in
| the jacket of the cable. That little twist they put in the pairs
| is excellent in isolating them from crosstalk.

That twist is a great little means to ensure induced signals,
whatever they may be, are induced in equal amount on both wires, so
they do not contribute to the actual intended signal that is a
differential between those two wires.

However, a risk exists when two different pairs are present next to
each other and each pair is twisted at the same pitch. The signal
carried by one can end up being induced differentially on the
other. So don't twist those power lines, or if you do, twist them
at a pitch with a ratio to the phone line twist that is not a whole
number.

CAT5 cable is an example. It has 4 different pairs twisting along.
Each of the pairs has a different twist pitch by design (unless
you get some cheap cable not manufactured correctly).

I do not have any technical knowledge of this area.

I would like to ask about a cable which has two or more twisted pairs
in it.

Is there is a greaterlikelihood of hum if I connect a "2 wire" phone
extension by using one wire from a twisted pair and taking the second
wire from a different twisted pair?

 

In alt.engineering.electrical gfretwell@aol.com wrote:
| On Tue, 4 Mar 2008 19:13:07 -0000, "Graham." <me@privacy.com> wrote:

|>It is quite difficult to induce hum into telephone wiring.
|>Use twisted pair cabling rather than the flat ready-made
|>extension cables.
|
| Exactly!
| The phone company has millions of miles of cable running right below
| power lines and hundreds literally touching each other in the jacket
| of the cable. That little twist they put in the pairs is excellent in
| isolating them from crosstalk.

That twist is a great little means to ensure induced signals, whatever
they may be, are induced in equal amount on both wires, so they do not
contribute to the actual intended signal that is a differential between
those two wires.

However, a risk exists when two different pairs are present next to each
other and each pair is twisted at the same pitch. The signal carried by
one can end up being induced differentially on the other. So don't twist
those power lines, or if you do, twist them at a pitch with a ratio to
the phone line twist that is not a whole number.

CAT5 cable is an example. It has 4 different pairs twisting along. Each
of the pairs has a different twist pitch by design (unless you get some
cheap cable not manufactured correctly).

--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2008-03-04-1516@ipal.net |
|------------------------------------/-------------------------------------|

 

On Tue, 4 Mar 2008 19:13:07 -0000, "Graham." <me@privacy.com> wrote:

"Foxtrot" <foxtrot@demo.invalid> wrote in message
news:Xns9A57AA15ACE8ED712E3@127.0.0.1...
I am in the UK and want to make several phone extensions.

QUESTION: I would like to know I this will increase the level of hum.

ISTR UK phones have a transformer and some other components to
neutralise hum but would that be good enough to prevent hum from a messy
setup like mine? Some details are below.

-------------------------

In my situation the phone extension wires and the mains wires will run
close to one other.

There will be about four or five additional extension phone sockets.

And in some phone sockets there will be a loose extension lead of approx
3 metres which will be almost ontop of curled mains flex


It is quite difficult to induce hum into telephone wiring.
Use twisted pair cabling rather than the flat ready-made
extension cables.

Exactly!
The phone company has millions of miles of cable running right below
power lines and hundreds literally touching each other in the jacket
of the cable. That little twist they put in the pairs is excellent in
isolating them from crosstalk.
Just don't use "straight through" door bell wire and you will be fine.

 

[Graham.]

"Foxtrot" <foxtrot@demo.invalid> wrote in message
news:Xns9A57AA15ACE8ED712E3@127.0.0.1...

I am in the UK and want to make several phone extensions.

QUESTION: I would like to know I this will increase the level of hum.

ISTR UK phones have a transformer and some other components to
neutralise hum but would that be good enough to prevent hum from a messy
setup like mine? Some details are below.

-------------------------

In my situation the phone extension wires and the mains wires will run
close to one other.

There will be about four or five additional extension phone sockets.

And in some phone sockets there will be a loose extension lead of approx
3 metres which will be almost ontop of curled mains flex

It is quite difficult to induce hum into telephone wiring.
Use twisted pair cabling rather than the flat ready-made
extension cables.
--
Graham

%Profound_observation%

 

[Foxtrot]

I am in the UK and want to make several phone extensions.

QUESTION: I would like to know I this will increase the level of hum.

ISTR UK phones have a transformer and some other components to
neutralise hum but would that be good enough to prevent hum from a messy
setup like mine? Some details are below.

-------------------------

In my situation the phone extension wires and the mains wires will run
close to one other.

There will be about four or five additional extension phone sockets.

And in some phone sockets there will be a loose extension lead of approx
3 metres which will be almost ontop of curled mains flex







--


max four x-post groups:
uk.telecom a.c.hardware a.e.electrical sci.electronics.equipment

 

[daestrom]

"Ivor Jones" <ivor@thisaddressis.invalid> wrote in message
news:63940jF26jn3fU1@mid.individual.net...

"CBFalconer" <cbfalconer@yahoo.com> wrote in message
news:47CF3D42.810AA5C9@yahoo.com
: : Ivor Jones wrote:

[snip]

: : I replaced your non-standard quote markers with
: : the normal '>'. Please don't use thos non-standard
: : characters. They foul up other software.

With respect, and without wishing to start a row, that's *your* problem. I
use non-standard quote marks for a purpose. If your system can't cope with
that, then it's up to *you* to do something about it. I have been using
the quote marks I use for several years and you are the first to complain.

Here's a third complaint. The only thing worse is those that post in html
and so some newsreaders won't automatically mark the quoted text at all.

daestrom

 

[daestrom]

"Ivor Jones" <ivor@thisaddressis.invalid> wrote in message
news:63cq0bF26robtU1@mid.individual.net...

"CBFalconer" <cbfalconer@yahoo.com> wrote in message
news:47D0B5CD.55C84978@yahoo.com
: : PCPaul wrote:
: : : Ivor Jones wrote:
: : : : "ehsjr" <ehsjr@bellatlantic.net> wrote in message
: : : :
: : : : [snip]
: : : :
: : : : : : Non-standard usage can make your posts harder
: : : : : : to : :
: : : : understand, and more difficult for others.
: : : : Apparently, : : you don't care. I'm just adding one
: : : : more response to : : let you know that your
: : : : non-standard usage is not : : appreciated.
: : : :
: : : : Ok, you're the *second* complaint in 10+ years.
: : : : When that figure gets to a noticable percentage, I
: : : : might sit up and take notice.
: : :
: : : Third. But don't worry about me, because *plonk*
: :
: : The only problem with a straight plonk is that other
: : peoples quotes of the plonkee shine through. The
: : advantage of that is that one has a chance to decide
: : the plonk should be retracted.

Indeed. But even three complaints in 10+ years (and I have my doubts on
the validity of at least one of them) is not worth worrying about. I post
a *lot* of articles on Usenet in 20+ groups, 3 complaints doesn't even
register. 3000 might, or even 300. But 3..? Try harder.

Most folks just ignore you instead of bothering getting sucked into
arguments. Life's too short to waste my time on you and your 'non-standard'
stuff.

<plonk>

 

[daestrom]

"Floyd L. Davidson" <floyd@apaflo.com> wrote in message
news:87pru8sgae.fld@apaflo.com...

CBFalconer <cbfalconer@yahoo.com> wrote:
In North America again (I don't know about elsewhere) the normal
phone uses 3 wires to connect to the two wires of the phone
circuit. The yellow wire carries the ring signal. Just disconnect
that and the phone won't ring, and the load is zero.

I don't recall any system in North America that put ring
voltage on a separate wire. The yellow wire is
generally not connected unless one 4-wire cable is used
for two separate telephone lines.

In North America the "normal" line uses only 2 wires.
The audio signal is applied between the "tip" and the
"ring" of a single pair. "Ring Current" and "Loop
Current" are also applied between the Tip and the Ring
of the same pair.

Commonly used drop cable has four wires: Green is the
Tip and Red is the Ring (positive and negative,
repectively for the DC loop current), while the Yellow
and the Black wires are not used. (Note that the DC
voltages used by telephone companies are negative with
respect to ground, hence for DC the Tip wire is at
ground potential, and the Ring wire has a negative
potential. But the Tip is not at ground potential for
Ring Current or for the audio signal.)

One configuration often seen includes a second line on
the same cable, using Yellow and Black as Tip and Ring.

Historically the Yellow wire was, for a few years, used
for a small AC voltage (nominally 6.8 volts) to power a
lamp circuit on some telephone set models.

Spot on. My parents had a 'princess phone' in the bedroom and a small AC
transformer in the basement fed the light with yellow/black. But all the
phones in my house are just R-G.

daestrom

 

[CBFalconer]

phil-news-nospam@ipal.net wrote:

Ivor Jones <ivor@thisaddressis.invalid> wrote:

.... snip ...

Indeed. But even three complaints in 10+ years (and I have my
doubts on the validity of at least one of them) is not worth
worrying about. I post a *lot* of articles on Usenet in 20+
groups, 3 complaints doesn't even register. 3000 might, or even
300. But 3..? Try harder.

BTW nobody has yet mentioned which piece of flaky software gets
upset by a : instead of a

It looks like maybe PCPaul's software, which identifies itself as
"Pan/0.132 (Waxed in Black)" might be getting them confused. ...

Piggy-backing, because Jones is plonked. Obviously he doesn't get
complaints, since all those who would complain have been ignored
and have plonked him. Most plonkers don't bother to advise the
plonkee.

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home.att.net>
Try the download section.



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

 

[kony]

On Fri, 7 Mar 2008 10:23:55 -0500, "daestrom"
<daestrom@NO_SPAM_HEREtwcny.rr.com> wrote:

"Ivor Jones" <ivor@thisaddressis.invalid> wrote in message
news:63940jF26jn3fU1@mid.individual.net...

"CBFalconer" <cbfalconer@yahoo.com> wrote in message
news:47CF3D42.810AA5C9@yahoo.com
: : Ivor Jones wrote:

[snip]

: : I replaced your non-standard quote markers with
: : the normal '>'. Please don't use thos non-standard
: : characters. They foul up other software.

With respect, and without wishing to start a row, that's *your* problem. I
use non-standard quote marks for a purpose. If your system can't cope with
that, then it's up to *you* to do something about it. I have been using
the quote marks I use for several years and you are the first to complain.


Here's a third complaint. The only thing worse is those that post in html
and so some newsreaders won't automatically mark the quoted text at all.

daestrom

I don't know about "only thing worse", there are lots of
worse things but make it a 4th complaint because it should
not be someone else's burden to cope with non-standard quote
marks - even if many newsreader apps can do so.

 

[Ivor Jones]

<phil-news-nospam@ipal.net> wrote in message
news:fqrka301cph@news1.newsguy.com

[snip]

: > What can be confusing to people is the double ": :"
: > usage. That makes
: > it look like you quoted with ":" what your previous
: > poster quoted with ":". So instead of that quoted text
: > being understood as the part of
: > the parent post, it gets misunderstood as part of the
: > grandparent post.
: > It also looks like you or your software replaced other
: > people's quoting character with ":" or ": :". Whatever
: > anyone uses, that should be
: > left as is (unless it is clearly broken).

It's OE Quotefix and I've found the setting that caused it to convert the
existing quote marks and I've disabled that, so they should now be as they
were.

Hope this helps.

Ivor

 

[Ivor Jones]

"kony" <spam@spam.com> wrote in message
news:08j3t3pi9cmhi3ci5r1lgvei4fmdg1l0po@4ax.com

[snip]

: > I don't know about "only thing worse", there are lots of
: > worse things but make it a 4th complaint because it
: > should not be someone else's burden to cope with
: > non-standard quote marks - even if many newsreader apps
: > can do so.

It shouldn't be *my* problem if your software can't cope.

Ivor

 

[Floyd L. Davidson]

"Ivor Jones" <ivor@thisaddressis.invalid> wrote:

"kony" <spam@spam.com> wrote in message
news:08j3t3pi9cmhi3ci5r1lgvei4fmdg1l0po@4ax.com

[snip]

: > I don't know about "only thing worse", there are lots of
: > worse things but make it a 4th complaint because it
: > should not be someone else's burden to cope with
: > non-standard quote marks - even if many newsreader apps
: > can do so.

It shouldn't be *my* problem if your software can't cope.

My software copes with anything reasonable, but not with
idiots who misconfigure their software.

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

 

[kony]

On Sat, 8 Mar 2008 02:43:18 -0000, "Ivor Jones"
<ivor@thisaddressis.invalid> wrote:

"kony" <spam@spam.com> wrote in message
news:08j3t3pi9cmhi3ci5r1lgvei4fmdg1l0po@4ax.com

[snip]

: > I don't know about "only thing worse", there are lots of
: > worse things but make it a 4th complaint because it
: > should not be someone else's burden to cope with
: > non-standard quote marks - even if many newsreader apps
: > can do so.

It shouldn't be *my* problem if your software can't cope.

Ivor

Yes it should because the whole point of usenet is the
simple and standard format it is presented in, versus say a
web forum.

 

[Ivor Jones]

"Floyd L. Davidson" <floyd@apaflo.com> wrote in message
news:8763vxrhze.fld@apaflo.com
: > "Ivor Jones" <ivor@thisaddressis.invalid> wrote:
: >>"kony" <spam@spam.com> wrote in message
: >>news:08j3t3pi9cmhi3ci5r1lgvei4fmdg1l0po@4ax.com
: >>
: >>[snip]
: >>
: >>: > I don't know about "only thing worse", there are
: >>: > lots of worse things but make it a 4th complaint
: >>: > because it should not be someone else's burden to
: >>: > cope with non-standard quote marks - even if many
: >>: > newsreader apps can do so.
: >>
: >>It shouldn't be *my* problem if your software can't
: >>cope.
: >
: > My software copes with anything reasonable, but not with
: > idiots who misconfigure their software.

It's not misconfigured. Just configured differently.

Ivor

 

[Ivor Jones]

"kony" <spam@spam.com> wrote in message
news:qn94t3di3ucrod0pqi0om416i6v87frqdj@4ax.com
: > On Sat, 8 Mar 2008 02:43:18 -0000, "Ivor Jones"
: > <ivor@thisaddressis.invalid> wrote:
:
[snip]

: >>It shouldn't be *my* problem if your software can't
: >>cope.
: >>
: >>Ivor
: >
: > Yes it should because the whole point of usenet is the
: > simple and standard format it is presented in, versus
: > say a web forum.

Plain text. If you have a problem with that, then I'm sorry but it *is*
your problem. It's people who post in HTML and other strange formats that
are the problem.

Although even Outlook Express can cope with that.


Ivor

 

[Graham.]

"Ivor Jones" <ivor@thisaddressis.invalid> wrote in message
news:63ecq9F26luhuU1@mid.individual.net...

"kony" <spam@spam.com> wrote in message
news:08j3t3pi9cmhi3ci5r1lgvei4fmdg1l0po@4ax.com
[snip]

: > I don't know about "only thing worse", there are lots of
: > worse things but make it a 4th complaint because it
: > should not be someone else's burden to cope with
: > non-standard quote marks - even if many newsreader apps
: > can do so.
It shouldn't be *my* problem if your software can't cope.

Ivor

I think software developers sometimes call this kind of dilemma Postel's Law
..

--
Graham

%Profound_observation%