Microfilter query

I think I know the answer to this, but have had a moment of self doubt.

I have ADSL Max on my line, and my phone and router are connected at
source - i.e. at the main BT phone point. I have a single microfilter
connected to that socket, with the ADSL feed to the router (obviously), and
the filtered signal to the phone, via a two way splitter for my Sky feeds
(to the Sky boxes). So essentially my line is filtered at the source
socket. I take it there is no benefit to adding microfilters anywhere else,
for example at the Sky boxes, as the two signals are already filtered at the
outset?

This may seem blindingly obvious, and it does to me, but I may be missing
some vital technical issue here.....

Thanks in advance.

Ian

"Mr Wiffy" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
>I think I know the answer to this, but have had a moment of self doubt.
>
> I have ADSL Max on my line, and my phone and router are connected at
> source - i.e. at the main BT phone point. I have a single microfilter
> connected to that socket, with the ADSL feed to the router (obviously),
> and
> the filtered signal to the phone, via a two way splitter for my Sky feeds
> (to the Sky boxes). So essentially my line is filtered at the source
> socket. I take it there is no benefit to adding microfilters anywhere
> else,
> for example at the Sky boxes, as the two signals are already filtered at
> the
> outset?
>
> This may seem blindingly obvious, and it does to me, but I may be missing
> some vital technical issue here.....
>
> Thanks in advance.
>
> Ian
>
>

I'd say that's the best way to do it. No mucking about if you add more
devices to the telephone system in the future, and you're unlikely to cause
problems with your ADSL connection (e.g interference, forgetting a filter,
etc) by taking it directly from the master socket.

Mr Wiffy wrote:
> I think I know the answer to this, but have had a moment of self doubt.
>
> I have ADSL Max on my line, and my phone and router are connected at
> source - i.e. at the main BT phone point. I have a single microfilter
> connected to that socket, with the ADSL feed to the router (obviously), and
> the filtered signal to the phone, via a two way splitter for my Sky feeds
> (to the Sky boxes). So essentially my line is filtered at the source
> socket. I take it there is no benefit to adding microfilters anywhere else,
> for example at the Sky boxes, as the two signals are already filtered at the
> outset?
>
> This may seem blindingly obvious, and it does to me, but I may be missing
> some vital technical issue here.....
>
> Thanks in advance.
>
> Ian
>
>
Correct (if I read your post/setup right) I assume you mean you only
have one
BT socket (the main one) and the phone/sky box are connected there.
If you have any extension sockets with phones connected, they must all
have microfilters even if you don't use the ADSL side.
The microfilters serve several purposes.
1) To split the phone signal off the line and to protect the ADSL signal
from upset when you lift a or several phones.
2) (only in the best microfilters) To put a filter in the ADSL socket to
add more separation from the phone signals and present a constant
terminating impedance to your modem.
3) (and again in best microfilters) to derive the 'ringing' voltage off
the phone line via a capacitor so that when the phone rings, the ringing
signal (which is usually split in the master socket and goes down the
'third wire') does not upset the ADSL signal.

Cheap microfilters often have neither 2 or 3 fitted and can cause
problems if you have loads of internal extension cabling or if you try
the dodge of removing the 3rd wire in the master socket to stop
interference as in (3)

If your MAX is working OK I should leave it alone. If it is dodgy and
you have an official BT master socket, it may be worth changing the
lower part of the faceplate for a proper one with filter built-in. These
are usually better quality than the separate plug-in microfilters.

Mike

I wouldn't worry if it's all working OK, but if you need a better
microfilter the adslnation ones are reckoned to be the best. I certainly
got a better S/N (3dB higher) and clearer sound on the phone with one
compared to a BT adsl faceplate.

Mr Wiffi, your set up is correct.
But it has been suggested that Sky boxes can cause problems and
that possible solution is to double up the filters for Sky connection(s).
Unfortunately it made no difference to my somewhat erratic BB.
Regards,
Martin

Mike:
>The microfilters serve several purposes.
>1) To split the phone signal off the line and to protect the ADSL signal
>from upset when you lift a or several phones.
>2) (only in the best microfilters) To put a filter in the ADSL socket to
>add more separation from the phone signals and present a constant
>terminating impedance to your modem.
>3) (and again in best microfilters) to derive the 'ringing' voltage off the
>phone line via a capacitor so that when the phone rings, the ringing signal
>(which is usually split in the master socket and goes down the 'third
>wire') does not upset the ADSL signal.

How can I tell if the microfilter has 2 & 3 ?
Or which microfilters have it ?
Thanks,
regards,
Martin

Martin² wrote:
> Mike:
>
>>The microfilters serve several purposes.
>>1) To split the phone signal off the line and to protect the ADSL signal
>
>>from upset when you lift a or several phones.
>
>>2) (only in the best microfilters) To put a filter in the ADSL socket to
>>add more separation from the phone signals and present a constant
>>terminating impedance to your modem.
>>3) (and again in best microfilters) to derive the 'ringing' voltage off the
>>phone line via a capacitor so that when the phone rings, the ringing signal
>>(which is usually split in the master socket and goes down the 'third
>>wire') does not upset the ADSL signal.
>
>
> How can I tell if the microfilter has 2 & 3 ?
> Or which microfilters have it ?
> Thanks,
> regards,
> Martin
>
>
Item 2 is a bit hard to check.

Item 3 is easier but really only relevant if you wish to disconnect wire
3 in the master socket to help ADSL problems. If there is no capacitor,
the 'ring signal' from teh master socket passes straight through.

If you have test meter you can check.

-------------
| o o o o | | | | |
| | | | | |
-------------

A R B B R A

Phone socket Plug viewed from pin side

if socket connection R (springy wire) is DC connected to plug pin
(strip) R then there is no capacitor inside.

To check DC connection, put your meter on ohms/resistance and the
connection will be high resistance if there is a capacitor and low if not


From my checks, BT ones are good (about £10 from Maplin) as are the
ones that come with speedtouch modems. Cant comment on others except
that the £1.25 ones from CPC (marked Commtel) are crap

Mike

Martin² wrote:
> Mike:
>
>>The microfilters serve several purposes.
>>1) To split the phone signal off the line and to protect the ADSL signal
>
>>from upset when you lift a or several phones.
>
>>2) (only in the best microfilters) To put a filter in the ADSL socket to
>>add more separation from the phone signals and present a constant
>>terminating impedance to your modem.
>>3) (and again in best microfilters) to derive the 'ringing' voltage off the
>>phone line via a capacitor so that when the phone rings, the ringing signal
>>(which is usually split in the master socket and goes down the 'third
>>wire') does not upset the ADSL signal.
>
>
> How can I tell if the microfilter has 2 & 3 ?
> Or which microfilters have it ?
> Thanks,
> regards,
> Martin
>
>
Hi again Martin

Alan said this in a similar thread. The site is very informative.


You can buy different quality filters built into a faceplate - the
components in a faceplate filter may be identical to those fitted in a
discrete micro-filter..

http://www.adslnation.com/support/filters.php

http://www.adslnation.com/products/xte2005.php



Mike