First we must understand all the potential trouble points in the telephone system, and what problems can occur:

Item	What can go wrong	Where is it located	Who fixes it	Likelyhood this could be the problem
DSLAM	Bad firmware, faulty hardware, poor connections, needs to be reset	Central Office	ISP	Possible
Line card	Faulty hardware, poor connections	Central Office	Phone Company	Not likely
Wiring from the DSLAM to your home	Cracked wiring, wet wiring, too close to electricalwires	Between the central office and your home	Phone Company	Likely
Demarcation block (demarc)	Full of moisture, corroded connections, loose wiring	On the side of your home or in the basement	Phone Company*	Not likely
Inside wiring	Cracked wiring, wet wiring, too close to electricalwires	Between the demarc and the phone jack(s)	Property Owner	Likely
Wall jack	Poor connections due to abuse, dirt, or painting over the jack	In your home	Property Owner	Possible
Phone cord	cracked or damaged wiring, cord too long, broken end connectors	Between the wall jack and your modem	Compute Owner	Likely
DSL Modem	Faulty hardware	On your desk	Computer Owner**	Possible
Ethernet cable	cracked or damaged wiring, broken end connectors	Between the modem and your network card	Computer Owner	Possible
Network Card (NIC)	Faulty hardware	In your computer	Computer Owner	Possible

Upgrading the phone lines inside your house may certainly help. But as you can see above, there are other things that could be at fault. So, before you put out a pile of money to have that work done, try connecting your modem directly to the demarcation point to verify if your inside wiring is to blame.

What is the demarcation point? The demarcation point (or demarc for short) is a small box on your phone line that defines the end of Bell's responsibility and the start of your responsibility for repair and maintenance of telephone wiring. The demarc is usually located on the outside of your house, although on some old houses it may be located inside. If you cannot find your demarc at all, contact your telephone company and either have them find it or install one. The maintenance of the demarc is generally the responsibility of the phone company.

There are several different styles of demarcs. They come in different shapes, sizes, colors, and the internal connectors can be different, but the function is the same. Usually there will be markings on the outside to identify it as a demarc - the phone company logo, or simply words relating to telephone or the abbreviation NID = network interface device - a fancy name for a demarc.

So once you've located the demarc, go ahead and open it. It may just pop open with a small screwdriver or even your bare hands. There also may be a screw that needs to be turned or removed to gain access to the inside of the box. If the demarc is inside, there may not be a box around it at all; you can identify it by looking for a block with some screw terminals with red and green wires connected to it.

NOTE: Telephone wiring is low voltage and unless you are standing in water holding both red and green lines when the phone rings, the risk of shock is very low. You should still take every precaution when working with any electrical wires, and if you are not comfortable working with phone lines, please consult either your phone company or a qualified professional.

There are two types of demarcs generally in use.

The first type is the older one, about the size of a deck of playing cards. This demarc contains only screw terminals inside. If this is the demarc you have, you will need to obtain a baseboard phone jack and a short piece of wire to temporarily connect your modem to. You can get a baseboard jack at Home Depot or Radio Shack. When you open the baseboard jack, you will see some red and green wires. You will also see some red and green wires inside the demarc. Connect red to red, and green to green. Connect a telephone to see if you get a dialtone (don't forget the DSL filter!) Disconnect the red and green wires that go into your home. You will have to reconnect these later when you're done.

The second type of demarc is much larger, about the size of a box of crackers. This one is much nicer than the screw terminals because it has standard phone jacks inside to allow you to quickly disconnect your home wiring from the telephone company wiring, and connect a telephone device directly to the demarc. If this is the demarc you have, you will not need to do any wiring. Just disconnect the phone jack, and plug your modem right in there with no DSL filter. Obviously you will not have telephone service once that jack is disconnected, but this won't take long.

Once you have your modem connected directly to the demarc, you will need to connect it to your computer. The best way to do this is to either move the computer in the house so it is as close to the demarc as possible. If you have a laptop, you can just take it outside. Or purchase a long ethernet cable and run it through your house temporarily. Do not use a telephone extension cord for this exercise; use as short of a phone cord as possible. You may even want to try a couple of short phone cords in case one of them is faulty.

Now, run some speedtests. A good speedtest is to download a large file from your provider's homepage, or Microsoft since those pages tend to deliver top speeds. You can also run some speed tests from this site. If your speed tests improve, then you know your inside wiring is to blame and is in need of replacement or repair.

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by MacGyver edited by KeysCapt
last modified: 2003-08-16 20:50:00