- OT? BT line polarity?
- Posted by T i m on April 13th, 2005
Hi All,
Sorry if this isn't strictly on topic but I wondered if someone could
confirm if telepgone line (LL) 'engineers' bother checking / keeping
the polarity of the 50V DC line voltage a certain way .. (I think they
used to be called A and B legs in my BT days but I was on electronics
repair not 'Holes n poles' or 'Subs apps') ;-)
If there is a right polarity, if so, which way round please (re 2 and
5 on the BT socket).
All the best ..
T i m
I was helping a mate sort a slow dial-up connection (aren't they all
<g>) and some of it was down to poor internal cabling (bad use of
'pairs' etc).
- Posted by Steve P on April 13th, 2005
See http://www.wppltd.demon.co.uk/WPP/Wi...telephone.html
"T i m" <news@spaced.me.uk> wrote in message
news:lpdq51lq961qpu2kjb2v5ch8uh7hgq19vm@4ax.com...
- Posted by T i m on April 13th, 2005
On Wed, 13 Apr 2005 15:45:36 +0000 (UTC), "Steve P"
<someone@somewhere.invalid> wrote:
Thanks for that Steve (bookmarked link).
So, it says "-48V to the B leg (J2) and 0V to the A leg (J5)"
I take it that these voiltage are WRT ground, so for a more 'real
world' answer I should see 50V on 5 WRT 2 ;-)
If so that makes remembering it easy .. 50V on 5 or the higher number
the higher voltage ;-)
Cheers ..
T i m
- Posted by Jock Mackirdy on April 14th, 2005
In article <d3jer0$hkp$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com>, Steve P
wrote:>
Top posting edited.
There's no point at all fiddling around with the wiring to get pos. and neg.
on particular wires. The BT network and BABT-approved apparatus are not
polarity-sensitive. Line reversals can occur whenever work is done on
external cables or flexibility points.
If you've got a modem that's sensitive to line polarity, try buying one
that's BABT approved.
--
Jock Mackirdy
Bedford
- Posted by vivian stanshall on April 14th, 2005
Maybe you didn't read the link? Too busy editing the post.
"Which way around they are connected usually doesn't matter but as Rick
Hughes kindly pointed out some modems (especially older USA sourced
ones) and some answering machines are fussy about polarity, so it's wise
if possible to check the voltage on the line and connect -48V to the B
leg (J2) and 0V to the A leg (J5)."
Jock Mackirdy wrote:
- Posted by T i m on April 14th, 2005
On Thu, 14 Apr 2005 14:28:21 GMT, Jock Mackirdy
<jock.mackirdy@ntlworld.com> wrote:
That was one of my questions, ta.
I haven't .. and the last time I might of bought a non approved modem
I believe it was a V.21 ;-)
All the best ..
T i m
