# Testing Dry DSL Lines



## wildleg

ask the phone company what the code is to dial to get the test tone.


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## Big John

wildleg said:


> ask the phone company what the code is to dial to get the test tone.


 The test tone they're putting in isn't from the CO, the techs are doing end-to-end tests, and they're actually hooking their Tempo tester directly to the conductors on the end of the line.

The only thing I can figure is their Tempo sources more current than my function generator, but I've measured voltage drop with the generator connected and I still have 7.5V across the pair.

I still don't understand how I'd be able to hear the tone from my function generator, but can't see it with any of my meters.

-John


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## Ty Wrapp

I'm a AT&T Service Technician and I don't understand your question. If you rephrase your question, maybe I can help.


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## mikeh32

I was kind of wondering the same thing...


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## Speedskater

Maybe your function generator set-up is also adding hum to the DSL line and confusing your frequency meter. I don't thank that you will hear much hum with the butt-set speaker. Hook the function generator up, but with the output set to zero and then do a signal voltage test.


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## Ty Wrapp

Speedskater said:


> Maybe your function generator set-up is also adding hum to the DSL line and confusing your frequency meter. I don't thank that you will hear much hum with the butt-set speaker. Hook the function generator up, but with the output set to zero and then do a signal voltage test.


Dry DSL does not have any voltage on it from the phone company. The term DRY means no dial tone. You should hear nothing at all on a DSL circuit. The OP says he is having trouble on a 2 pair DSL line. DSL uses 2 conductors, 1 pair. I have even seen it run on one conductor when the other conductor was open. It will also run over a pair that is so dirty that it would affect dial tone on a line share circuit. I still have no idea what the OP is trying to do!


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## Speedskater

Ty, go back and re-read post #1 than read my post #6.


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## Big John

Let me clarify:

I don't know what the technical term for these lines is, the phone company themselves has called them everything from "dry DSL" to "dry pair" to "leased line." They are simply copper pairs with no amplification and no battery voltage.

We are using two of these pairs for each telemetry circuit. The TELCO put a network interface card on each end for testing purposes, but there's no amplification there. 

I'm not a phone guy, so bare with me if what I say isn't precisely accurate.

-John


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## mikeh32

so, what is it you are trying to test for?


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## Speedskater

I think that Big John wants to be able to test the circuits in the future, before calling the phone company.


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## Big John

Speedskater said:


> I think that Big John wants to be able to test the circuits in the future, before calling the phone company.


 That's exactly right. Because getting their techs out and organized is a massive headache. 

Per my original question: I don't understand why none of my meters can see my 1004Hz on the other end of this line, and I'm hoping someone familiar with the test can shed some light on what the TELCO was doing that I must be doing differently.

-John


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## Ty Wrapp

Big John said:


> Let me clarify:
> 
> I don't know what the technical term for these lines is, the phone company themselves has called them everything from "dry DSL" to "dry pair" to "leased line." They are simply copper pairs with no amplification and no battery voltage.
> 
> We are using two of these pairs for each telemetry circuit. The TELCO put a network interface card on each end for testing purposes, but there's no amplification there.
> 
> I'm not a phone guy, so bare with me if what I say isn't precisely accurate.
> 
> -John


Back in my Southwestern Bell days we had a circuit called an AEV. This circuit ran from customers primary location to the central office then back to the customers secondary location. It was a dry pair primarilary used for alarm circuits. I installed several in local Police departments. The phone company only supplied the pathway between the customers 2 end points,with the customer connecting their equipment to each end. Does this sound like the circuit that you are trying to trouble shoot?


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## Big John

Ty Wrapp, that definitely sounds like it. The only difference is we are using two of those pairs for each of our telemtry circuits, one transmit and one recieve. 

Also, the TELCO landed each end of these circuits on a card which I believe is called a "Data Station Termination" card, and it has the ability to amplify (which we aren't using) and the ability to do loop-back tests.

When they do end-to-end loop-loss tests and look at dBm, how much power are they sending through the line, do you know?

-John


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## MDShunk

I have an old Halcyon and the paperwork says it's making the test tones at 48V and cuts off at 24 mA. I have a feeling their unit may have been constant current rather than a certain voltage.


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## Ty Wrapp

Big John, sounds like what you have is a 4 wire designed circuit. That is out of my area of expertise. Normal dial tone runs at 48v, 23ma. I have seen 4 wire circuits run at 180v. Sorry I cant help!


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## 8V71

Big John....is your function generator output single ended (signal and ground) or balanced? DSL is a balanced pair so I would assume the telco's device tests it balanced. The output signal quality at the end of the wire between single ended and balanced would be HUGE.


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