atcomsystems.ca/forum Forums TDM Business Telephone Systems Avaya - Lucent Telephones & Systems POTS Voltages

Hi All

We recently had a new phone system installed, an Avaya IP Office system. Since the install almost all lines show a "Pre Ring" indication only during the hours of 6am to around 6pm.

The installer has checked everything he could and opened a ticket with Avaya. Avayas response is it is a POTS problem contact Verizon. I cannot belive it is a POTS problem as it affects 18 out of 25 lines that function perfectly with the old Comdial system. I have no idea as to what to tell Verizon if I did call them.

We did some testing today to try to pin it down and found some weird voltages.

Some lines show 48 to 51 volts Tip to ring where others are around 37 to 38 volts, I thought the standard was 48 volts. The 48 to 51 volt lines show about 0.25 volts Tip to ground where the 37 to 38 volt lines show 7 to 8 volts Tip to ground, I thought Tip should always be close to ground.

I also get about 8 volts AC Tip or Ring to ground and 15 Volts on others.

I should mention that some of the lines are direct copper to the CO about 4 mies away and others come from a terminal unit located about 3000 feet away. When direct copper goes bad Verizon usuly switches us to the terminal. A few times when they have done this they failed to option the cards correctly and left us with either a ground start line or a line that would not cut over on ring, it would wait till the ring voltage droped before the call cut over.

Could the weird voltages be card option problems or is this new stuff 37 to 38 volts and not Tip grounded.

I should mention that when this false "pre ring" happens their is no change in the DC or AC voltage and no sound on an amplified Butt Set that would indicate the line is doing anything.

Sorry for the long post but I do not want to cause a Verizon truck roll unless I can prove something is wrong.

Well, you have definitely done your homework. You are correct about the remote terminal; the lines with higher voltages are likely the ones coming from the remote. Unfortunately, the voltages you have measured aren't really out-of-line. The target voltage is 48 volts DC, +/- 10% at the premises. Very often, the voltage leaves the CO at 52 volts so that a typical copper loop can be compensated.

The lines that measure in the 30's do concern me, but I doubt that they would cause the trouble you are reporting. If anything, the problem would be low volume complaints, especially on conference calls.

As for AC voltage, the only time that should be present is during a ring cycle. If you are picking up tiny amounts, that can be attributed to AC induction from power lines. You will probably pick up much more between tip or ring to ground. Anything more than a few volts might be a problem. Even though ringing voltage is AC, it is at 30-40 Hz so measurements with a regular meter might not be accurate.

Tip is always grounded, even on the new pair gain equipment. It's a basic fundamental of POTS lines and if it changed, there would be millions of dollars worth of test equipment that would have to be thrown out the window.

Did you measure loop current? That's the real killer. You will need to place an ammeter in series with one side of each line while going off-hook to get an accurate measurement. This should be between 23 and 27 mA in a perfect world.

It is a bit ironic that these same lines didn't bother the Comdial system, but I am assuming that it was an old one. They were a lot more tolerant to line variations than today's equipment.

I think I need to comment as well.

You stated:

"Some lines show 48 to 51 volts Tip to ring where others are around 37 to 38 volts".

SO, which lines are failing?

That is, are the 37 to 38 ones the bad boys, or is the failure with the other ones?

My guess is the lower voltage ones are your bad boys.

Do you see a pattern, based on this question?

Ed and Merlinman both make valid points to investigate. On the lines close to the RT (remote terminal) the loop current could be excessive. However, you will probably not be able to get Verizon to do anything about it - you will have to make compensations. Mike Sandman makes current regulators that work very well. Also, as Merlinman suggested, is there a pattern of voltage readings on the lines that are failing?

Bill

Thanks for the replys

The lines that I am having problems with do not follow any pattern as far as voltages

Loop current runs from a low of 24ma to 37ma so that looks to be within acceptable limits

All the lines that show 7 to 8 volts Tip to ground are also the lines that also show 37 to 38 Tip to ring. I think these are the lines that come from the remote terminal.

I should be expecting to see Tip close to ground but it's not and it should be. Am I correct?

The AC readings are to ground and I would expect them as I am reading the line unbalanced, AC Tip to Ring is about 4.1 mv on all lines. There is no change in AC or any sound in an amplified butt set when the Avaya system reports "Pre Ring"

All the lines talk fine, ring normaly when called, I do not know what else I can do

...the Avaya system reports "Pre Ring"

What the heck is "reports" Pre Ring? What exactly is the system doing?

-Hal

"Pre Ring" Lights the appearance light for the line and also shows up in system monitor. It is normal for it to appear during the first ring while the system waits for caller ID.

The system never passes the first ring to the stations to prevent a fast pickup from scrambling the caller ID.

During the times the system is showing "Pre Ring" the line cannot be picked up or intruded on.

Ok, many systems work that way. Never saw it called pre-ring.

I think you ruled out any anomaly on the CO lines. Even more puzzling is the 6AM to 6PM thing. Wonder if it's crosstalk from other ringing lines owned by another company that conducts business during those hours?

Then too, you have to remember what you are dealing with- IP Office. That's the next place I would look.

-Hal

I would think if it where cross talk I would hear it on the amplified butt set I have bridging the line and see some AC on the line, I hear and see nothing.

The thing that concerns me most with the lines is that some are not Tip Grounded and have 7 to 8 volts to ground where others are within .25 volts of ground

As I said, Avaia wants me to call Verizon but what do I tell them? The lines work fine with a Butt set the Comdial and a 2500 set. I know where this is going already and it's a bad feeling.

The lines work fine with a Butt set...

That's all Verizon wants to know. All Verizons going to tell you is "Yo problem is with yo PBX, call yo vendah"- and this time I think they are right.

If there is no problem with anything other than your IPO, well, what does that tell you?

Ahem, who is your vendor anyway?

-Hal