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What Are Allowable Leased Line Specs - Attenuation, Noise, eq, etc.?

What Are Allowable Leased Line Specs - Attenuation, Noise, eq, etc.?

What Are Allowable Leased Line Specs - Attenuation, Noise, eq, etc.?

Having recently inherited a radio system that has a lot of leased analog audio phone lines, many of which have some kind of trouble, I would like to know some kind of general specs that the phone company is obligated to maintain. It seems hard to find anything on Google, maybe because POTS is thought to be on the way out?

I am looking for figures like

-max permissible attenuation end to end (16 dB is what I have)
-max dB deviation between frequency response
-amount of broadband hiss/60 Hz hum picked up on a quiet line
-anything else you think I should be looking at

The phone company is AT&T/Pacific Bell and the lines are all within about 20 miles although some do run from one CO to another.


RE: What Are Allowable Leased Line Specs - Attenuation, Noise, eq, etc.?

Are these POTS lines, or are they point-to-point circuits? The most likely is circuits, and the type of circuit will dictate the specs - most of which are spelled out in the tariff documents. There are MANY types of analog circuits - the differences often dealing with loss, noise, etc, just the aspects that you're seeking. Look at the bill or request a Customer Service Record (CSR) - that SHOULD have a USOC code. You may need to do a USOC lookup to decode. Then find the appropriate tariff.
If they are POTS lines, again, you'll need to know the exact type as they're not all the same. Trunks are different than ancillary lines.
Good luck.

RE: What Are Allowable Leased Line Specs - Attenuation, Noise, eq, etc.?

Finding the actual phone bill or USOC code could be difficult, but I have managed to come up with some spec numbers using the clues you provided. The lines are point-to-point analog radio circuits. I am still having a little trouble understanding exactly what it is supposed to be, though. The specs that I am concerned about are these:

Loss deviation (or variation) ±4.0 dB - what does this mean? Does it mean that the line as a whole is allowed to vary by that much over some period of time?

Attenuation distortion:
(I know what it means but I need a little help figuring out how to apply the numbers)

404 to 2804 Hz | -2.0 to +10.0 dB

Does this mean that 404 is the reference and the attenuation at 2804 is not allowed to vary from 404 by less than 2.0 or more than 10.0?

Right now the major problem is that the attenuation numbers in the telco plant are these:

404 | 13.3
1004 | 12.4
2804 | 26.1


RE: What Are Allowable Leased Line Specs - Attenuation, Noise, eq, etc.?

Without knowing what you're paying for, there is no way to know if it is operating within spec. IF the spec is between -2 and +10dB between 404 and 2804 Hz, AND if your're measuring losses outside of that range, then you're not getting the performance that you seek. But that's a lotta IFs...

RE: What Are Allowable Leased Line Specs - Attenuation, Noise, eq, etc.?

At this point, I am more seeking to be sure I understand what the definition of terms such as "-2 to +10 from 404 to 2804 Hz" actually is. This is the spec for the "attenuation distortion."

Does this mean that we consider 404 to be 0 dB and measure how much 2804 passes relative to it? Or is the reference 1004?

There is another figure called "loss deviation" or "loss variation" which is ±4.0 dB. Is this a variation across frequency or over time or something else on the x axis?

I have found the tariffs and standards for different types of lines and they are all similar enough that it is not of very much concern. My application is not very demanding. What I am missing is definition of terms.


RE: What Are Allowable Leased Line Specs - Attenuation, Noise, eq, etc.?

Those private line circuits are called analog voice or data circuits. I worked for a paging company in California for 17 years and am very familiar with their design in 2-wire and 4-wire versions. They fall under the Special Access tariffs. For technical specifications you want to find the Tecnical Reference documents from Telcordia. Something like Voice Grade Special Access Service TR-NPL-000335. Pacific Bell's engineering department did publish some similar documents, which I have, along with the Telcordia manuals. The circuits can have special equalization depending upon the transmitter's requirements, etc. To get an inventory of your circuits, you want to contact your Pacific Bell account manager. That person may not exist or may be in Texas. Arrogant Thugs & Thieves has decimated the Pacific Bell landscape! It may be very interesting what information they may or may not want to provide you.


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