We have phone and DSL coming into the NID in the garage. I was having some problems with the service, so the rep asked me to go to open the NID and plug a phone directly into the voice jack and see if I had a dial tone. I opened the NID and saw three phone jacks with a plug in each, and to the right of each jack were the four screw terminals for twisted pairs. I'll number the terminal screws 1 through 4, with 1 being on the far left, and 4 being on the far right.

The 1st/bottom jack was the voice line. The 2nd/middle jack and terminals it were labeled with a red/green ADSL sticker. The 3rd/top jack and set of terminals are unused.

The bottom/voice terminal screws have the blue and blue/white wires connected to them (blue/white on the screw 1, blue on screw 4). The ADSL terminal screws only had one wire attached the them. The solid brown wire is attached to terminal screw 3, but nothing was attached to the screw 2. The brown/white wire isn't connected to anything. I've attached a photo of the NID to show the wiring I tried to describe.

Our phone bill shows that we are paying for 3M/640k DSL service, but when I run a speed test (downloaded from cnet) it shows we are only getting 860k down/330k up. It has been slow for a long time now and I'm not sure what the cause may be.

Does it sound like there is a problem with the wiring? Should there be another wire connected to the #2 DSL terminal screw?
Is this type of signal loss (dropping the download speed from 3M to 860k) normal? Do we need an in-line filter?

I know if I call the phone company again they will say that everything is fine on their end and charge a bunch to come out and look at it, so I would like to do some research on this end first. Any advice would be greatly appreciated. Thanks!

DSL "Whole House" Filters will have 2 wire in and a place for 2 pairs out. Blue pair is first pair and will many times be Voice Line/ Line 1. I actually use Brown pair myself for DSL.
If you remove the jack that the Modem plugs into and it has Blue pair connected, it may not be Whole house filtered.
If the brown pair is ised for the Modem, You need to connect the other Brown wire.
You can always try it and see the results, then go to a site like T1 | Business Broadband & Voice Provider | Speakeasy Inc. (http://www.speakeasy.net/speedtest) for a Speed test. Good Luck
I never tried DSL with 1 wire.

Thanks for the reply, but the issue is in the demarcation box put up by the phone company that converts the "street copper" into the feed that goes to all the inside jacks. That's where only one DSL wire is connected, not inside a filter box. I don't own a filter yet, but will probably get one later, after I get this figured out.