Calls Dropped on Hold

[skinswin]

This is an ongoing problem for over 2 years since the building was constructed. Intermittently when an incoming call is placed on hold the caller is dropped. It happens on 6 different lines. Some are in a hunt group, others are not. It doesn't happen at any particular time, the amount of calls, weather conditions, etc. Nothing consistent at all. We can go for over 1 week without dropping a call on hold, then we will drop 4-6 in an hour. We only drop calls when they are placed on hold or they are parked.

We have been working with the telephone company to try and resolve this problem. We had a Norstar system, that was then upgraded to a BCM 400. We have tried 2 BCM 400's. We have replaced all cables to the BCM, all incoming and outgoing wires, punch down blocks etc. The local Telco's Nortel expert has gone through our software settings and verified everything is correct. Telco has checked all voltages, line currents etc. We have placed balanced loop current attenuator on all lines. All to no avail.

Any input you can give into this problem would be greatly, greatly appreciated. The telco is grasping at straws, and the next step is to re-route our dial tone through another CO.

Thanks in advance!!

 

[ISDNman]

Yup. That is what I wanted to double check.

OK, with an analog meter that was a good test.

Definitely let us know what you find on the ground. You might even want to be or borrow a clamp on ground resistance meter.

Ant idea what type of protector the telco is using at the building entrance. If the are carbon protector elements it might be worth getting the Telco to change them to gas tube on at least a few lines.

A few other "long shot" things to check (all of these are very slim, but it never hurts to try).

Are tip and ring the same polarity (at the PBX) on all lines? If not reverse the crossconnects on those that are backwards to get them the same.

If they are all the same you might try reversing all of them.

Check the lines for common mode noise. If you have a noise test set short tip and ring together and measure c-msg noise to ground (from the shorted pair to ground).

If you don't have a noise test set try measuring the voltage from the shorted pair to ground. If you get more than a few volts see what kind of current you get from the shorted pair to ground.

Is the Telecom ground (from the protector) bonded to the power ground per the last couple of versions of the National Electrical Code.

 

[skinswin]

ISDNMan,

First off, thanks so much for all your help.

I will try to get all of things on your suggestions checked out today and tomorrow. I will also check with the telco about the protectors, NEC codes as far as grounds and everything else.

Thanks for being patient with me as I said I'm not a tel-comm. guy, but rather a radar guy. So this is all new to me. I'm trying to keep up with you guys, so please bear with me.

I'll post later today or first thing tomorrow with updates.

Thanks,

Jeff

 

[ISDNman]

Believe me Jeff,

I know how it is when the boss says "your smart enough to figure this out so do it" even though you know it is not in your area of expertise.

Thank goodness in cases like that there are forums to turn to.

That brings up another question. Who installed the various systems? It makes you wonder if something was done wrong from the start.

 

[skinswin]

The first Comdial was installed by a vendor.
The subsequent Norstar's were installed by an IT guy at the office.

Our regional "telephone expert" install our first BCM400. He's an expert because he installed the first one in his office first!!!

I installed the 2nd BCM 400 and have since installed 2 more at other offices. No other offices(we have 125+ offices in US) has this problem utilizing the same equipment/setup procedures.

So one would think perhaps it is a wiring issue, ground, telco protectors or something. Could the handsets(I know it's a stretch) have anything to do with this?

Thanks,

Jeff

 

[ISDNman]

>So one would think perhaps it is a wiring issue, ground, >telco protectors or something. Could the handsets(I know >it's a stretch) have anything to do with this?

Well, certainly not with the Comdial. I am careful never to say "never" so I won't rule it out but it seems unlikley. It is *possible* you got a bad bunch of phone sets that have something wrong, but it sure is a stretch.

Seesm more likely a case of some sort of electrical interference. I'd definitely rule out grounding.

First find the electrical entrance. Follow form the service panel and look to see if there is a ground conduct that goes to a ground system outside the building..

Next, do the phone come inothe building in the general vacinity of the power? On a new building they should, assuming the local munipality has adopted NEC or something stricter. That is because the phone protectors should really hae their own ground rod which then should also be bonded over the the power ground.

Also measure resistance from the power entrance (shutoff switch) to the power gound. Should be a fraction of an Ohm.

Next measure from the Telco protector to the Telco ground rod and also the power ground rod. Should be a fraction of an ohm in both cases.

Does the PBX run on 120 or 240 volts? Does it have it's own dedicated branch circuit? If not see if you can determine what else is on that circuit. If it runs on 120 measure from each side of the power outlet to the ground pin. From one side to ground you should see ~120 volts to ground. From the other side you should see almost nothing.

Have you had any other equipment that has blown up or is unreliable at this location? You might have a floating neutral, but int hat case you might well have seen problem with computers or other electronic equipment that just seemde dto be unreliable here.

Best of luck

 

[skip555]

if your not doing it now you need to start a log of when they are droped , which line and which ext . you might see a pattern .

could it be a bad or a few bad phones ?

possible /not probible

if the same peaple always answer the phone and put callers on hold swap out their phones

the log serves two functions primarly, it makes it look like your on top of things while you sort the problem out

it might evan show you a pattern to work from .

the systems you took out what happended to them ?

 

[skinswin]

ISDNMan,

I'll do as you suggested and check all those things. We have a seperate ground bus/bar from building power. We have no other probs/losing equip. or anything in our building.

Skip555,

The systems we took out were used in other offices, with no problems. We have 47 different DN's and they all drop calls, we are a manned office 24/7/365 so the drops occur regardless of who is using the phones. In addition I have kept a log for the past year and a half. We've been working with the telco this long on this prob. We've looked for patterns(rain, snow, sunny, cloudy, heavy call log, certain lines, certain times, etc.) There is no pattern at all.

As I write this we have gone 8 days with no dropped holds. Why? It's anybody's guess. The system is on a UPS. If I take it off the UPS I risk the possibility of losing the phones during a severe weather event and that just can't happen. I work with the National Weather Service and the meteorologists need their phones.

 

[skinswin]

Checked all the grounds. Everything is less than 1ohm of each other.
120vac plug to ground=119.7v.
120vac reversed to ground= 270mv

Telco Protectors= Not carbon, I'm assuming there solid-state, the telco tech said he could be out Monday to install gas tube one if we want and to check the tip/ring to ensure their all the same.

Also checked telco protector to ground. Well under 1 ohm.

If I have forgotten to check something let me know. Wouldn't these readings all be normal until we start dropping the calls placed on hold? Just curious. Either way we have a base line. Loop current good on hold and off hook. No diff. Ground into building excellent.

Thanks,

jeff

 

[ISDNman]

Jeff,

Once the Telco says they are all the same polarity at the demarc, then check them right at the block going to the PBX.

 

[Trotski]

Ask the telco if a line concentrator/pair gain system is in use to your building, I have had a lot of problems with calls dropping on analog lines in conjuction with Alcatel RAM8 line concentrators particularly on very long lines

The problem ussally goes away when the cct is placed on a physical line.

 

[phuzzy42]

Ground start/Loop Start mismatch? Answer Supervision problems?

Steve Harmon
Greenfield, Indiana

 

[ttech]

I had the same exact problem with a Merlin Plus years ago. It would intermittently drop calls on hold. I tried everything, new KSU phones etc..

Finally I used an extension cord and hooked it to another outlet and never had the problem since. I guess a copier, laser printer or fridge was on the same phase or line as the system

Don