cat 5 cable

[Adam_151]

http://en.wikipedia.org/wiki/IEEE_802.3af[/QUOTE]

I'm still waiting for a version of that which works over a 802.11 system...

 

[NotSureAboutDIY]

Does anyone know the answer to this? Otherwise I'm gonna have to look it up.

It's a differential signal. Whether one core carries the inverse of another is a largely philosophical argument.

I must be being thick because I can't see the philosophical argument here.
Differential is term I'm quite happy with, and I agree that it describes the signal carried by each pair in UTP cable, but inverse? I can see a reason for doing it, being to increase the signal to noise ratio on the wire, but I didn't know that this was a technique used with 10xyBASE-Tz.

And I still don't know...

I think what theyre getting at softus is, if the signal is relative to the other line, then what level you call each one is only in reference to the other, I'm assuming (and this could be due to a lack of understanding) that as theyre linked at each end current flows equally and opposite so inverse isnt such a bad description, but if youre after a definative I havent got it!

 

[Softus]

I think what theyre getting at softus is, if the signal is relative to the other line, then what level you call each one is only in reference to the other, I'm assuming (and this could be due to a lack of understanding) that as theyre linked at each end current flows equally and opposite so inverse isnt such a bad description, but if youre after a definative I havent got it!

Thanks for showing willing, stewski, but I think you're on the wrong track.

Firstly, the current in a UTP is negligable - this is the network phyical layer with small voltages, high impedance, and really quite miniature currents.

I understand, and agree, that the voltages in a given twisted pair are relative to each other, but I don't yet see, tehnically (i.e. no philosophically), that one is the inverse of the other.

This is a trivial point, and mostly just me being picky, but I don't see the point in posting something that is (a) vague, (b) factually incorrect, and (c) not followed up by the person who posted it.

 

[NotSureAboutDIY]

I think what theyre getting at softus is, if the signal is relative to the other line, then what level you call each one is only in reference to the other, I'm assuming (and this could be due to a lack of understanding) that as theyre linked at each end current flows equally and opposite so inverse isnt such a bad description, but if youre after a definative I havent got it!

Thanks for showing willing, stewski, but I think you're on the wrong track.

Firstly, the current in a UTP is negligable - this is the network phyical layer with small voltages, high impedance, and really quite miniature currents.

I understand, and agree, that the voltages in a given twisted pair are relative to each other, but I don't yet see, tehnically (i.e. no philosophically), that one is the inverse of the other.

This is a trivial point, and mostly just me being picky, but I don't see the point in posting something that is (a) vague, (b) factually incorrect, and (c) not followed up by the person who posted it.

Im not sure why the magnitude of the current is relevant.
Im going basic here but we're talking (all be it small) transient DC
V=ir so i is small and r is big so what?

obviously I'm assuming (complete with transformers) one at each end what weve got is a circuit which would mean that one way or tother what we've got is equal and oppposite (be it current or voltage) as the resistance/impedance is fixed.
[edit]
just read what i wrote DC on transformers, oh dear its been a while since I used anything the taught me

this probably is simplistic as I've not dealt with this level of detail on the physical layer but hey, to be honest even if Im wrong and the whole things ac I cant see (assuming its a circuit) how they can be anything other than equal and opposite at any finite point in time?

 

[Softus]

Im not sure why the magnitude of the current is relevant.
Im going basic here but we're talking (all be it small) transient DC
V=ir so i is small and r is big so what?

Er, you're right - magnitude is irrelevant; I got sidetracked.

obviously I'm assuming (complete with transformers) one at each end what weve got is a circuit which would mean that one way or tother what we've got is equal and oppposite (be it current or voltage) as the resistance/impedance is fixed.

Yup - the reason I got sidetracked is that I should have said that I believe the fact that there is a current to be irrelevant (please read on).

this probably is simplistic as I've not dealt with this level of detail on the physical layer but hey, to be honest even if Im wrong and the whole things ac I cant see (assuming its a circuit) how they can be anything other than equal and opposite?

Yes, they are, or probably are, but I'll put my point more clearly now.

...cat5 requires the inverse of the signal to be carried in the second wire in the pair".

If he's referring to the fact that, as you rightly point out, each twisted pair is some kind of circuit, then he has a very funny way of going about it.

I think it's more likely that he was minded to remember the differential nature of the signal pair, but didn't explain it very well. The third possibility is that he's just plain wrong, but if he doesn't follow up the post then we'll never be sure.

 

[NotSureAboutDIY]

well as always wiki has good info

http://en.wikipedia.org/wiki/Differential_signaling

can't say I miss the electrial engineering course now we bring it all back.
Im going to get my head back into the upper layers where it belongs

 

[NotSureAboutDIY]

oh yeah and no one ever did answer if this
cat 5e/6e or other utp cable can be an improvement from aerial down to my telly box, some one must have tried it?

 

[plugwash]

without the correct baluns it would be useless, even with the correct baluns you'd be pushing the cable to its specification limits and beyond.

for high quality arial downleads just use good quality satalite grade coax.

 

[NotSureAboutDIY]

without the correct baluns it would be useless, even with the correct baluns you'd be pushing the cable to its specification limits and beyond.

for high quality arial downleads just use good quality satalite grade coax.

tis what I'd assumed uhf goes upto 3G dunnit? cheers pluggy i'll stick with my double screen sat cable.

any tips for a loft install?

 

[Softus]

well as always wiki has good info

http://en.wikipedia.org/wiki/Differential_signaling[/QUOTE]
Well, this certainly agrees with jwilliams, although for all we know it was written by him.

I'll shut up now.

 

[ban-all-sheds]

I did do a diagram, but didn't get round to posting it in time.

The brown curve is the signal you wish to transmit.

The voltage difference between black and white represents the signal.



I guess the philosophical point is whether you imagine that there is a 0v reference as shown...

 

[Softus]

I guess the philosophical point is whether you imagine that there is a 0v reference as shown...

Well if the word "inverse" is used then I don't think there's any doubt.

However, my original question was technical, not philosophical, that being whether there were two signals that were mutually inverted, or whether instead there was one signal with the other being a reference that remained unchanged (except for externally induced noise).

According to the non-authoritative Wikipedia information, differential signals within a pair are always the inverse of each other.