ADSL "high open" condition

[SarelSeemonster]

So, I'm busy creating another Major Backup of all the important stuffs on my computer (which must be the most boring and time-consuming yet undeniably critical task ever imaginable) when I discovered the following two posts that I saved as text files for later reference sometime during 2007/2008. I live in an ancient little village in Centurion where the current copper-line infrastructure must have been installed shortly after World War II and then left to rot instead of being properly maintained by our esteemed fixed-line operator.

I distinctly remember the joys of trying to explain the symptoms below to numerous Telkom helpdesk monkeys which was extremely frustrating, especially since I'm but a mere end-user myself and don't have an Electrical Engineering degree. In the end, after numerous phone calls, Telkom refs, contact form submissions and HelloPeter posts, my problem was "fixed" by ripping out cables at strategically-located points which then forced Telkom to install a brand spanking new cable. I ended up paying for said new cable but in hindsight it was well worth it considering the rapid decline of my blood pressure as well as a much-improved "best effort" service from Telkom (less "effort" on my part, more "best" from Telkom).

Anyhoo, I for one found it quite interesting and hopefully someone who recognizes these symptoms will then at least have a name for it:

If you find your DSL modem dropping off line or losing sync when your phones are not in use and syncing ok when you use the phone, you have a condition likely caused by a "high open".

The phone line consists of a pair of copper wires originating at a Central Office (CO) or Remote Terminal (RT) and running through various cables, cross connect boxes, and other splices until it reaches your Network Interface Device (NID). From the NID your inside wiring brings the line to your telephone and modem jacks.

Each splice, interconnect, and terminal on the line between you and the phone company's equipment must be a tight, low-resistance electrical connection for the line to work well.

When you use a telephone a small amount of electrical current flows in the copper wires and this current, which carries your voice, also helps keep the splice points in the line clean and tight. This is commonly called "sealing current" because it seals the junctions.

Lines exposed to air can either oxidize slightly or sometimes corrode heavily depending on conditions. This deterioration at splice points in copper phone cable can cause this "high open" condition. The bad junction creates high resistance, effectively creating an "open" in the line, and DSL signals might fail to cross it, or be weakened by the attempt. When a phone is picked up current begins to flow and the resistance drops during the call. If its just a light case of oxidation you may not notice any change in sound quality. A bad case of corrosion might cause audible clicks, pops, and static on a voice call.

Since DSL signals do not draw current on your line, high open conditions can lead to the degradation of the DSL signal to the point of losing sync. When you use your phone you seal the faulty connection and DSL signal returns. When you put the phone on-hook and stop the current flow the high open returns, sometimes right away - sometimes with a delay, and your DSL loses sync. High opens can also cause other oddball conditions, such as sync loss when the phone rings.

To fix this situation you should first test NID your modem at your NID. Plug your DSL modem directly in to the test jack at your NID and see if sync is solid there.

If you do not have good sync at your NID then you need to call your phone company and report trouble on your line. It is recommended that you first report it simply as a Plain Old Telephone Service (POTS) problem of "static" on the line and request a metallic loop test. This is the automated test done when ever a phone line problem is reported using the normal phone trouble number. It should spot a high open condition. If you talk to a trouble operator do not mention anything about DSL at this point, it only serves to confuse the issue sometimes.

If the test spots the high open problem the telephone company will track it down and fix it, which should lead to normal DSL function again.

If you do have solid sync at the NID, then the problem is someplace in your inside phone wiring. Check all the screw terminals at the NID for tight wire connections. Check any splice points in your internal wiring for corrosion or bad junctions, especially in moist or damp areas. Disconnect any lines to jacks that are no longer used and double check all wires in jacks and look for clean contacts on plugs and sockets. Plug a phone in at your modem's jack and make sure you have clear dial tone and no static.

If this does not solve the problem then start your DSL service provider's trouble procedures.

You're helping a friend set-up his computer in a new home. You've untangled his cables, thanked his wife for labeling them, and connected his peripherals. It's time to connect him to the World Wide Web. You connect his DSL modem, lights start flashing and the DSL modem fails to sync. You verify your connections; cables, filters etc, and decide it's time to call the phone company.

Here's where things get interesting. While plugging your way through the phone company's voice prompts, you notice that you have sync. Since there is no need to talk to tech support when the gods of bits and bytes intercede, you cry FM and hang up the phone. In this case, the "F" doesn't stand for frequency and the "M" stands for magic. I'm sure you can figure out the "F" word. Unfortunately, you lose sync as soon as you hang up the phone. You start to call tech support, and again the bits and bytes start to flow! You realize that your friend's DSL only works when the phone is off the hook.

Ok, hot shot you're on:

What would cause a DSL connection to work only during a telephone call?


The answer is below the fold. In other words, continue reading "A DSL Problem With Class" for the solution.
This is a condition known as a "High Open" occurring when oxidation forms on exposed splice points in the copper connecting you to the phone company. The oxidation deteriorates the connection by increasing resistance at the compromised splice. The oxidation creates a condition similar to a break, or open, in the line. While DSL signals do not draw current across the line, the current required for a voice call "seals" or "wets" the line minimizing resistance essentiall bridging the artificial gaps.

Cool, it's the phone company's problem, right? Maybe it is; maybe it isn't. In most cases, the phone company is only responsible for wiring up to the point it enters your house at the Network Interface Device (NID). Once it enters your house it is usually your wiring and your problem. I know Sweetness, you pay for the wiring maintenance plan every month, and the phone company will repair your wiring at no additional charge. Otherwise, the phone company will charge you to repair the wiring in your house. You can determine if the problem is on your side of the NID by plugging your modem directly into the test jack at the NID.

 

[Budza]

Good stuff to know. Someone googling sometime will find this helpful.

 

[who.is.michael]

Tx, enjoyed your narration…