Do I need a ADSL Filter?

Hi, I have a BT Line which will just have the adsl modem plugged in
with no phone, will this require a filter?

(E-Mail Removed) wrote:
> Hi, I have a BT Line which will just have the adsl modem plugged in
> with no phone, will this require a filter?

Nope.

<(E-Mail Removed)> wrote in message
news:(E-Mail Removed) oups.com...
> Hi, I have a BT Line which will just have the adsl modem plugged in
> with no phone, will this require a filter?

No...

Filters are only required for phones on the line. No phones = no filters

In uk.telecom.broadband, (E-Mail Removed) wrote:

>Hi, I have a BT Line which will just have the adsl modem plugged in
>with no phone, will this require a filter?

As others have said, no. But you may need a "cross-over" BT-RJ11 lead:

<http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&rd=1&item=5190622867>


--
Nigel M

"Time may be a great healer,
but he's a lousy beautician"

Nigel M wrote:
> In uk.telecom.broadband, (E-Mail Removed) wrote:
>
>> Hi, I have a BT Line which will just have the adsl modem plugged in
>> with no phone, will this require a filter?
>
> As others have said, no. But you may need a "cross-over" BT-RJ11 lead:
>
> http://cgi.ebay.co.uk/ws/eBayISAPI.d...tem=5190622867

Also make sure no one knows the number as incoming ringing can cause you
problems

In uk.telecom.broadband, kraftee wrote:

>> As others have said, no. But you may need a "cross-over" BT-RJ11 lead:
>>
>> http://cgi.ebay.co.uk/ws/eBayISAPI.d...tem=5190622867
>
>incoming ringing can cause you problems

Why? The modem is connected to the line in exactly the same way.


--
Nigel M

"Time may be a great healer,
but he's a lousy beautician"

Nigel M wrote:
> In uk.telecom.broadband, kraftee wrote:
>
>>> As others have said, no. But you may need a "cross-over" BT-RJ11
>>> lead:
>>>
>>> http://cgi.ebay.co.uk/ws/eBayISAPI.d...tem=5190622867
>>
>> incoming ringing can cause you problems
>
> Why? The modem is connected to the line in exactly the same way.

All I can tell you is that it can knock the 'modem' out of synch, as to the
why's & wherefore's I'll leave to you lot to argue about it....

> All I can tell you is that it can knock the 'modem' out of synch, as to
the
> why's & wherefore's I'll leave to you lot to argue about it....
>
>
I know that "ringing" is a large (40V?) AC voltage as opposed to the much
smaller (9V?) regular voltage. Any sudden big waveform will have sidebands
at higher frequencies so perhaps this is enough to mess up the modem.

That said, I though the ADSL filters basically "passed through" the ADSL
straight to the modem. [Disclaimer - any components connected in parallel,
ie. the phone side filters, will still affect the, at first glance,
unfiltered side ;-) ].

Since your modem will probably come with a filter, I'd just plug it in. For
another reason, the cable from the modem will probably have an RJ-11
connecter and the filter will provide BT-socket to RJ-11 conversion for you.

Paul DS

Paul D.Smith wrote:
>> All I can tell you is that it can knock the 'modem' out of synch, as
>> to the why's & wherefore's I'll leave to you lot to argue about
>> it....
>>
>>
> I know that "ringing" is a large (40V?) AC voltage as opposed to the
> much smaller (9V?) regular voltage. Any sudden big waveform will
> have sidebands at higher frequencies so perhaps this is enough to
> mess up the modem.

Make ringing voltage about 75-90v AC & the normal wetting/speech voltage at
50v (depending how far you are away from the exchange) & you would be inside
the ball park..

The only times I've fitted a Modem/router direct to a telephone socket, with
no filters has been on ICB lines or lines which have been specially provided
for the service, so the number is not known (not even to the end customer
sometimes, which could make for interesting faulting at a later date :-) )

As you stated it could be because of the AC pulses causing sideband
interferrence which could cause a loss of synch but in practice a filter is
normally used & anybody who jumps up & states that the adsl port isn't
filtered, it's pass thru, have got to remember that the filtering can & does
put a load onto the non filtered side.

It was on this very froup recently that we had at least one person reporting
that they couldn't get a stable connection unless they did use a filter (on
a dedicated line for the ADSL, nothing else attatched).

Please remember I am commenting from the practical side of things, not the
theoretical...

In uk.telecom.broadband, kraftee wrote:

>in practice a filter is
>normally used & anybody who jumps up & states that the adsl port isn't
>filtered, it's pass thru, have got to remember that the filtering can & does
>put a load onto the non filtered side.

It depends on the impedance of the line, but yes the filter is in
parallel with the line, so will have an effect.

My router's instructions showed two diagrams: one with a splitter, and
one with a filter in the phone side only, a subtle difference.


--
Nigel M

"Time may be a great healer,
but he's a lousy beautician"