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| DIY filters. |
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| message from Ian Stirling on 27 Jun 2005 |
I've got a lot of assorted inductors/... here.
My existing filter isn't quite cutting it (9dB SNR loss on inserting
a DECT/analogue cordless phone (oddly, both the wired phones I tried
were -0.2dB).
Can anyone point me at some filter designs, or the specs for them?
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| Phil Thompson replied to Ian Stirling on 28 Jun 2005 |
the specs are in the G.dmt standard, dslforum.org or the like.
BT's SIN at www.sinet.bt.com has extracts and various impedance
requirements. SIN 346.
http://www.adslnation.com/support/filters.php may be interesting.
the dodgy phone will have to go :-)
Phil
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| Ian Stirling replied to Phil Thompson on 28 Jun 2005 |
Thanks.
Unfortunately, the dodgy phone won't have to go, I'll have to get it
filtered adequately.
I'll have to put the scope on it to see if it's outputting any obvious
crap.
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| Paul King replied to Ian Stirling on 28 Jun 2005 |
Not wishing to rain on your parade, but I hope you are aware that connecting
non-BT approved equipment (in this case your DIY filters) to their network
is subject to prosecution and a *HEFTY* fine if/when they find out :)
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| Joker7 replied to Paul King on 28 Jun 2005 |
: Ian Stirling wrote:
: > Phil Thompson <phil.thompson@spamcop.net> wrote:
: >> On 27 Jun 2005 23:49:43 GMT, Ian Stirling <root@mauve.demon.co.uk>
: >> wrote:
: >>
: >>> Can anyone point me at some filter designs, or the specs for them?
: >>
: >> the specs are in the G.dmt standard, dslforum.org or the like.
: >>
: >> BT's SIN at www.sinet.bt.com has extracts and various impedance
: >> requirements. SIN 346.
: >>
: >> http://www.adslnation.com/support/filters.php may be interesting.
: >>
: >> the dodgy phone will have to go :-)
: >
: > Thanks.
: > Unfortunately, the dodgy phone won't have to go, I'll have to get it
: > filtered adequately.
: > I'll have to put the scope on it to see if it's outputting any obvious
: > crap.
:
: Not wishing to rain on your parade, but I hope you are aware that
connecting
: non-BT approved equipment (in this case your DIY filters) to their network
: is subject to prosecution and a *HEFTY* fine if/when they find out :)
: --
: paul.g.king@theobviousdsl.pipex.com
: Reply address is spamtrapped. Remove theobvious for valid e-mail address
:
I was of the understanding that your side of the wall is your and not their
network,ie no need for BT approval.
Chris
kick-butt.co.uk
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| Chip replied to Joker7 on 28 Jun 2005 |
<snip>
Technically anything connected to any phone jack that has access to an
outside line in the UK is "directly or indirectly connected to a
public telecommunications system" and therefore should have BABT
approval (note, BABT= British Approvals Board for Telecommunications
and is not part of BT). However, how good their enforcement is I don't
know, I can't imagine them wasting the money in tracking you down for
using a homemade and well designed filter or indeed any piece of well
designed equipment.
OTOH, if you were to build a device that had a failure mode consisting
of connecting the telephone line to 240 volts, (think Arthur Daley
special imports), they probably _would_ expend the resources to track
and prosecute, after the first phone company employee got hurt.
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| Ian Stirling replied to Chip on 29 Jun 2005 |
In theory, you require BABT approved cable clips, the way the regulations
are worded.
And indeed I suspect the number of prosecutions for using equipment
marked specifically as not to be connected to the BT network closely approaches
0.
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| kraftee replied to Ian Stirling on 29 Jun 2005 |
But the charges raised by BT engineers significantly higher after they've
been called in to investigate why the line isn't working properly...
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| Dave replied to Ian Stirling on 29 Jun 2005 |
My phone causes the ADSL to drop when it rings. I've fitted a second filter
in series and that's solved the problem.
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Archived message: DIY filters. (UK Broadband - ADSL, ISP, Routers etc.)
