Telephone cable - which one do I need?

[JoeJoe]

Looking to add a couple of extensions - all indoors.

Do I need a 4-core cable (Screwfix quote 18134) or a 6-core cable (quote

17421)?

TIA.

[Chipmunk]

For a normal UK exchange line, 4 core will do. If the price difference isn't bad, 6 core (3 pair) might be a better idea if the wiring's difficult to get at, it gives you a spare pair if one goes wrong. Only terminals 2,3,4 and 5 need to be connected (One of those is the earth and isn't really needed but its there so why not LOL) Terminals 1 and 6 are not used on domestic phonelines

HTH

[JoeJoe]

It does - thanks a lot.

[David Hearn]

I'd recommend the 6 core if you can afford the difference (I haven't checked).

When I wired in our new church building's phone/network cabling I was pleased 6 core was used (for the phones, CAT5 was used for network). All the wiring was already done by the builders etc, but my task was to terminate the ends into a patch panel etc. On one cable, there was a short on one of the pairs that had been used - wasn't at either end of the cable, so somewhere in between. Seeing as the building was practically finished at this point, replacing the cable wasn't really an option. As there was a spare pair, I just switched to this pair for this socket and everything worked.

D

[Andy Dingley]

May as well use either 4 or 8.

4 is simple and makes your phones work. If you want any more than this, Cat5 is the thing to go for. 6 core phone is pretty much extinct in the middle - we're moving away from complex phone extension systems done by complex wiring, and any "business phones" that needed 6 cores are superceded by things that want a full network conenction, or at least cat5 structured cabling.

The main thing to get right is to do phones (pushdown IDC connectors) in solid core and alarms (screw terminals) with stranded. Use the wrong typoe of core in the wrong conector and you will have connection troubles.

[Christian McArdle]

I only use Cat5e for telephone wiring. It will run 2 phone lines, 4 if you cheat. It is much higher quality than standard phone cable and specially rated for voice as well as network cabling.

Christian.

[Adrian C]

Consider using Cat5/6 type cable, it's cheap enough. Eventually domestic phones may be upgradable to IP type devices in the not too distant future.

-- Adrian

[jim_in_sussex]

I came to grief recently by assuming cat6 is upward compatible with cat5. IM(very limited)E cat5 & 6 are possibly equivalent at low frequency, but not at high.

I bought cat6 at the same price as cat5 would have been, on basis that hard work is pushing the cable thru & it would provide some future proofing, whilst using the lower cost cat5 plugs and sockets.

Various web sites (eg clarity.it) suggest you can use a cat 5 cable to link the front to the back of the house to take normal speech tel traffic; & to bring the broadband feed from the back where the wireless router is to the whole-house filter in the BT socket at the front. It didn't work on the broadband side. However it worked when I replaced the bb link with ordinary tel cable.

Presume that it has something to do with the hf impedance of the cat6 compared with the cat5. (the term 'image impedance' rings a faint bell, but that could be a ghost from a long forgotten shady past). dc testing showed no problem - errors only appeared at broadband frequencies. Unfortunately I have no hf test gear to be sure.

Looking at the cables in cross section, Cat5 is simply 4 twisted pairs run touching in a pvc tube, whilst cat6 has a central dividing pvc core keeping each twisted pair separate. Also I see the Maplin (not, incidentally, where the cat6 was bought) catalog has various values for C of cat5, but doesn't specify the capacitance of cat6, so it could be there's a query on cat6 capacitance matching.

[Stefek Zaba]

[ tale of woe deleted ]

I'd be hugely surprised if this were repeatable; insulting as it seems, I think it likeliest you miswired when you used the Cat6; since you say you did DC tests, the likeliest oopsie was a split pair...

Stefek