A brief question about microfilters

lucernarian

Hi all,
A friend of mine has been having problems with making calls and his DSL losing sync.

If you do not have a phone beside the DSL modem that is being used, is it okay then to simply plug the modem straight into the wall socket and leave the other phones filtered?

Or do you need to use the twin filter whenever there are phones in the house? I did a search for this but the answer wasn't clear.

kaizersoze

To_be_confirmed wrote:

Hi all,
A friend of mine has been having problems with making calls and his DSL losing sync.

If you do not have a phone beside the DSL modem that is being used, is it okay then to simply plug the modem straight into the wall socket and leave the other phones filtered?

Or do you need to use the twin filter whenever there are phones in the house? I did a search for this but the answer wasn't clear.

No. The DSL side of the double filter is "unfiltered".
You can plug the modem directly into the socket.
Do a bit of troubleshooting though. One of the single filters may be faulty.
He's not using a DECT cordless phone by any chance?

lucernarian

Thanks for the reply kaizersoze,
He does have a DECT phone allright, but no matter what phone he answers the dsl light goes once the call is taken. BT support told him the master filter was faulty but the problem affects all phones in the house.

What would using a DECT phone mean?

kaizersoze

They are known to cause problems, like you described, for alot of people with BB for some reason. While others are using them without any problems. Get him to unplug it from the line and just use an ordinary wired phone to see if the problem goes away.
You can also try plugging the BB modem into the Eircom master socket and plug the DECT into an extension. Try a few different configurations.
Try and make sure first that one of the single filters is not faulty.
Remember that everything thats plugged into the phone line needs a filter (Sky Digibox, fax machine, moitored alarm, etc), not just the phones.

8track

DSL dropped with me if I made a phone call while phone and modem were connected through a dual microfilter. Tried different microfilters, standard Corrib corded phone, Siemens DECT cordless. However, dsl stays up if I connect phone to a different socket through a single microfilter and modem straight into wall socket. BT sent me a new modem. With it DSL stays up while using phone with phone and modem connected through same dual microfilter! However, DSL now drops frequently when phone is not in use! Tried disconnecting phone again with modem straight into wall but still disconnecting and reconnecting every 10-30 minutes!!

Taliesin

Technically you should not be able to use the DSL line if the 'modem' is unfiltered or if a phone is unfiltered. If the 'modem' is unfiltered it will pick up voice and drop everytime there is an incoming call. This doesn't always happen but technically thats what does. If the phone is unfiltered, you just get noise on the line. As far as I am aware the DSL side of the filter is not a straight through channell but a filter filtering out anything below a certain frequency (in the same way as the phone side filters out anything above a certain frequency). Having an unfiltered modem plugged in will get you line noise on the modem, just like a Dial-up dropping the line if the extension was picked up.
Other things to look at is bad wiring on the extension cabling, too much equipment on the on the line (REN over 5) and dodgy filters. The last is more common thanb you think.

Tal

lucernarian

kaizersoze wrote:

No. The DSL side of the double filter is "unfiltered".

Taliesin wrote:

As far as I am aware the DSL side of the filter is not a straight through channell but a filter filtering out anything below a certain frequency

This is the problem, there is contradicting evidence about this on the net. BT say a filter is needed, some websites say it is not, if there is no phone present.

I asked here because I hope there would be the same answer all round:(

Snaga

The modem does not require a filter.

Every port you have anything else plugged into does require a filter however. (Phones, Fax, modem, sky box, alarm etc..).

These filters stop the higher frequency noise generated by these devices from screwing with the modem.

On a 'dual filter' the Modem side is unfiltered - The phone side is filtered.

kaizersoze

The evidence I have is that I have never used a filter on the BB modem in the 3 years I have BB. It's plugged straight into the Eircom master socket. Never had a problem.