DSL Filter/BT socket?

Please could any one tell me whether I need to install a DSL filter between the BT master socket and my router, which is a Speedtouch 580 and is presently plugged directly into the master socket, or are filters only required on extension sockets, in use, elsewhere in the house?
Regards
Ben

You need a filter on all telephones, sky boxes, alarms etc. It is not necessary to use a filter with the router unless you want to have a telephone etc in the same location.

Thanks Dave.
Regards
Ben

A much more elegant solution, provided you only need an ADSL signal at the master socket, is to use one of the master socket faceplate filters, as sold by clarity.it or adslnation. That will provide filtered phone connections to all your other sockets, avoiding the need for a filter at each point.

The faceplate ADSLnation sell, is it as good as the official BT modified plates that Clarity sell? I've noticed my filter has been letting some of the ADSL signal leak over to the phone side lately, so i'd like to replace it soon.

The BT faceplate sold by Clarity is in fact a Pressac product and available from several places including us.

I have compiled what I hope is a useful list of master faceplates that I know about, and the prices including VAT, when following links remember some web sites show ex VAT prices. I have also included the total cost to order one faceplate as that is all that most people need.

ADSL Nation XTE-2005
Contains the XF-1e circuit design with filtered & unfiltered IDC connections and has been tested with ADSL 2.
ADSL Nation

Got both types and at my last house, which was a long line, not very noisy though, the ADSL Nation filter did make some improvement over the Pressac one.

Aimed at newcomers to ADSL rather than anyone in particular.

Might I just add that it's often necessary to use a filter in this position for its physical rather than its electrical characteristics. I suspect that many newcomers to DSL are confused when presented with an RJ11 plug and a BTS socket.

The term "ADSL filter" is I think very misleading to the uninatiated and suggests that it's the DSL signal that's filtered when of course, the opposite is true.
I think that if ISPs were to explain the process a little with their introductory packs, we'd see fewer problems for new users. It should also be clearly stated that the two filters that are usually supplied by them may well not be enough to meet the requirements of many households.
With the above in mind, it's probably worth briefly explaining the process of delivering the DSL signal from time to time using laymans terms.

The DSL signal is composed of much higher frequencies than the normal voice signal and can therefore be easily "piggybacked" on to the normal voice signal at the exchange which of course allows the two seperate systems to be delivered to the consumer over the same pair of wires. This is vitally important as the UK telephony infrastructure simply wouldn't be able to meet the demand if seperate systems were necessary.

Without going into the specifics, a DSL filter can be viewed as a sentry or a gate which blocks all signals that are below a certain frequency but allows higher frequencies through without hindrance. The composite signal enters into the filter and is presented as two seperate signals at its output. The DSL signal is available via the smaller, squarish socket while the voice signal is available via the wider phone type socket.
As we already know, the DSL signal consists of high frequencies while the voice signal consists of low frequencies. Therefore, the filter provides a simple method of seperating the combined signals that arrive at your master socket back into the original two useable signals.
Although it's all pretty simple, it's important for the user to keep in mind that the filter "blocks" the voice side of the signal and leaves the DSL side to pass through it unhindered. It can therefore be seen that all telephony equipment except your DSL modem or router must be connected via a filter.

The above is a very simple explanation that tries to avoid using technical terms and such "black arts" as signal propogation, transmission and manipulation etc. In attempting to achieve this, some fundamental issues with the system have not been covered but the end user can minimise or even negate the chances of these issues arising by using a few simple rules:

• Ensure that any internal cabling is up to the job and preferably of a BT approved
  type.
• Ensure that any internal cabling is sensibly routed and avoids electrical wiring etc - Particularly if that wiring feeds inductive devices such as PIRs and central heating switches etc.
• Ensure that any extension sockets etc are up to standard, correctly wired and terminated.
• Note carefully all the household equipment that uses your telephone system. Don't forget Sky Digiboxes and alarm systems etc.
• Be aware that some telephone equipment, DECT handsets and FAX machines for example, can interfere with the ADSL signal.
• Where an NTE5 type master socket is fitted, a simple method of disconnecting all internal wiring and equipment is available to you. Don't be afraid to use this when fault finding.
• Remember that filters can and do fail. Also remember that some filters are of a much higfher quality than others and opting for quality can often lead to a not insubstantial improvement in your connection speed and/or stability.
• It's worth noting that the laws of physics basically dictate that the higher the frequency of a signal, the more it degrades as it travels from the exchange to your master socket. It therefore follows that higher speed services such as the 8Meg ADSL MAX service are often more problematical than lower fixed speed services.
• Malware and virus etc infections are often responsible for what the user deems to be a slow connection. See final note.
• If you ask your ISP to call out BT to investigate a problem and they find that the problem was your responsibility, you could find yourself landed with a bill of

  Edited by Deadbeat (Mon 02-Apr-07 18:00:48)

Ahhh, must have changed them since I bought mine then!

Mine is an official BT faceplate that had unfiltered IDC's put onto the back by Clarity. There was a long leadtime of a couple of weeks due to them being made on demand. I did recall them ditching them for pre-made ones but didnt pay attention.

Will have a look into buying a new one then, as theres a consistant hissing sound on the filtered ports when my DSL is synced

Yes it was the case that Clarity were the first to add unfiltered terminals by modifying the original Pressac supplied model for BT. The ready modified version came about because we went to Pressac and offered to place a sizable order if they would make the modification to the design at production. As a result they made the changes and the modified version is now readily available to all Pressac customers and now most of the faceplates they build are already modified to include the unfiltered terminals.

Sorry to say but you have your understanding back to front. An ADSL filter is an accurate name for an ADSL filter because its job is to filter out the ADSL signal. An ADSL filter is essentially a low pass filter (although designs are often more complex than that) that lets the low frequency voice signal through and blocks the ADSL.

I know your post was well intentioned to help people better understand how ADSL works. My correction is not personal I'm just trying to avoid further confusion caused by incorrect information.

My original post was prompted by problems with my adsl connection - BT standard faceplate, Zen 8000 Active - Speedtouch 580, - which has been fluctuating quite a lot since teams of BT engineers worked on overhead lines in the area last December. Severals teams were in the immediate area for six weeks or more.
Now waiting for BT to investigate - initial report within six working hours promised - must say I am more than a little apprehensive about outcome.
Trying to eliminate any possible problems on my side of connection. Any advice would be appreciated. Could any one tell me whether Micro Filter problems are a very likely cause of my massive drop in download speeds? Have filters on four extension sockets, one DECT and three analogue 'phones. All filters are Speedtouch ADSL filters and were supplied by them when I bought the router.
Thanks for any advice offered.
Best regards
Ben

So, as you sell both Pressac and XF-1e based filters, which design is better? My line isn't marginal, but did recently have a (now repaired) line fault which prompted me to look into my modem and filter.

I always thought the BT one was the best, but is the XF-1e really better? Would I see any change like a tiny increase in SNR levels or anything, and most importantly, will I still be hearing a small hissing sound on the Voice side from my ADSL?

Filters do fail, you need to eliminate whether one of them has gone faulty.

I've got both types at my new property (the XTE was out of stock when I got my ADSL connected). The line at this property is running a solid 8 meg connection (Zen 8000 Active) and TBH I didn't notice much difference between the two filters though the SNR is marginally better with the XTE, but that could be attributed to better contact in the socket and a few other things.

Unfortunately all the data I had to compare them has been lost due to HDD failure in my Linux server.

I'll grab one of them then! I don't hear any hiss when using my Speedtouch dangly filters, so a replacement Faceplate filter should do the job nicely!

You shouldn't hear any noise on the line, if you do it is probably because the ADSL signal is leaking through the filter. The XTE-2005 is a better design than the Pressac version. We only sell the Pressac one because some people ask for it and some places sell them at rediculous prices, so we may as well supply them at a reasonable price.

Yes I was aware that was the reason I was hearing hiss from the DSL signal. Will be ordering an XTE-2005 later on this evening. Still pondering whether to replace my ADSL2MUE with a ST585v6 though...

Quite often the cause of the hiss is the phone. Many phones have electronic amplifiers in them (especially DECT) which have automatic gain controls in them to prevent feedback. Some filters do allow a small amount of the HF ADSL signal to come through, and this is heard as a hiss in these phones. If you still get hiss with the XF-1e (which I believe is the best filter out there), then you may need to consider new phones.

In reply to:

---

Be aware that some telephone equipment, DECT handsets and FAX machines for example, can interfere with the ADSL signal.

---

I think you'll find that it's usually the other way around, especially when "cheap and cheerful" ADSL filters are in use.

If a filter is not doing its job properly then some of the ADSL signal reaches the telephone equipment. This may or may not result in audible interference on the phone equipment but also results in a distorted version of the ADSL signal being fed back onto the line by the telephone equipment that is not designed to handle ADSL frequencies. This then increases the noise, lowering the SNR margin, generally causing a slower connection. This is why quite often just changing a filter will result in a speed increase.