I notice that a lot of "telephone extension kits" as seen in the
shops, are supplied with flat cable. Does this mean the pairs are not
twisted? And if so, are there any implications to this?
I've just bought some own-brand telephone cable from CPC. It is the
white round cable with twisted pairs inside. Following the advice on
the earlier thread, I bought the 2-pair, 4-conductor cable. I notice
there is a lot of space inside the white insulation. Is it supposed to
be like this or is it because I bought a cheap brand? Does the
manufacturer use the same outer insulation for the 3-pair and 4-pair
cables and is this why there is space in my reel because these "extra"
pairs are missing?
On Wed, 23 Sep 2009 23:03:37 +0100, Roger Mills wrote:
I'd say it's not suitable for use a on a line that is used for ADSL
full stop. The filter filters the POTS side not the ADLS side, if
this flat, untwisted, cable is used pre filter then any interference
it picks up is connected directly to the modem. Depending on the
level of this interference and the common mode rejection of the
modems line circuitry it could have a very bad affect on the rates
the ADSL will run at.
Even use post filter, on the POTS side, I wouldn't be happy about.
If the pairs aren't twisted it can upset your ADSL signal, but of course the
extension kits work fine for the audio telephone service.
Telephone cable isn't normally that tight in it's outer, don't know why
They are not twisted and because of this are much more susceptible to
external interference. You probably have broadband and this type of
extension could well cause interference to the broadband signal,
reducing your bandwidth.
It is always like that and has always been like that. Even the several
thousand pair cable used to be fairly loosely packed.
If packed tight, it would end up with the twists concentrating
themselves into kinks, with untwisted lengths between the kinks,
and also adjacent pairs locking twists against each other
(each pair should have different number of twists per metre
to stop that from happening over a long cable run).
Phone cable only needs a very few twists per metre in theory,
but is almost always made with very much more because it's
easier to make sure you don't end up with parallel runs where
the twists ran off into little clumps. If you go back to hundreds
of pair paper spaced cables where that's not an issue, they're
something like 1.5 or 2.5 twists per metre (I can't recall the
[email address is not usable -- followup in the newsgroup]
Thanks for all the reassurance. I had not thought about all the twists
knotting together and flexibility for corners etc.
I don't know if there was any confusion but I'm not using the flat
cable; that's why I bought this reel to replace the flat cable
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