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!!

 

[Trotski]

Check Earthing at all points in your network are at the same (or close) potential.
Intermittant noise or spiking(sharp rise in level) can fool a phone system or indeed some types of line concentrators used by Carriers into releasing calls.
This can be caused by other electrical devices especially if close attention to earthing practices(within the communications network and/or the Electrical system) are not followed.
hope this helps.

 

[GHTROUT]

Unless you, personally, have experienced this problem yourself - on your phone more than once, the probem does not exist and it is a case of hysteria

If you HAVE had this happen first hand, on your phone, it is probably conincidence.

My comments based on the action steps you gave taken. The telco and her underground/arial feeds don't know that they are on hold - and being systems that,in reality, can be gounded with yarn and still work, I supect there is more to thas than equipment or software failure.

Just a viewpoint - and I will accept being wrong.

But 26 years of this...I am a really good guesser

~

http://www.GHTROUT.com/

 

[skinswin]

The grounding (Earthing?) has been checked for all components on the network. As far as it being a coincidence, I don't think 30 dropped calls over a 2 day period when calls are placed on hold is truly a "coincidence", but I am not an expert.

Thanks for all the input,

Jeff

 

[skip555]

do calls ever drop while in progress , or only when on hold ?

 

[mforrence]

I agree with where skip555 is going... if they ONLY drop while on hold, it is VERY likely to be your telephone equipment. Many systems have a timer that is used to determine the drop pulse duration - see if your system has such a timer. Normal setting is in the 450 ms range - set yours out to 900ms or so and see if it makes a difference. If it's too far out, "real" disconnects won't be recognised, most often causing voicemail to continue recording a message once the caller has disconnected. Good luck.
Mike

 

[skinswin]

The calls only drop when placed on hold. Once you place a call on hold the call drops within 1-3 seconds. If the hold works at first then a call will stay on hold just like it normally works. However, if it is going to drop a call it occurs when the call is first placed on hold. It is totally intermittent.

We have had 3 different Norstar systems and 2 different BCM's installed and the problem continues. We have also replaced all cabling, wiring, blocks etc.

I have also tried adjusting the time from anywhere from 200ms to 900ms. The Central office is set to 800ms.

Thanks so much for the input.

Jeff

 

[skip555]

if it only drops on hold then its not the telco or cabling

like GHTROUT observed the telco and cabling dont know the call is on hold .

so it has to be the norstar

have you posted this in the norstar forum ?

 

[skinswin]

Skip555,

I'm curious as to why you think it is system related when we have had 5 different systems installed. I did place this over in BCM board, but I only have 1 response yet.

Thanks so much,

Jeff

 

[skip555]

jeff

you need to understand what's happening , when you make or receive a call you are completing a circuit , tying the tip and ring together from the phone company. when you hang up you break the circuit , tip and ring are no longer connected.

so when you put a call on hold your equipment keeps the circuit connected but transfers the handset funcionalty to a diffrent path (within the phone system ) to allow you to complete other functions (make another call , use the intercom , have someone else pick up the call etc ).

as far as the dialtone provider and building cabling are concerned the call is still active. so for whatever reason the norstar is deciding that the call is no longer valid and is dropping it.

if it where cabling or dialtone provider then we should be seeing active calls drop also in about the same numbers.

does this happen to be VOIP dialtone ?

is it always the same extnsion or extensions that lose calls ? or are they pretty much spread out among extensions and areas of the building ?

are you on a ups ?

 

[skip555]

heres something else to try ,next time a call drops push the line key right away and see if the caller is still there .

I had that happen about 10-12 years ago on a tie onyx, calls on hold would dissapear but if you pushed the line key right away they where still there.

as I recall it took a lot of tweaking of system timers to solve that one

 

[ISDNman]

What was the loop current when measured?

Assuming that is 30 mA or greater (yes, I know the limit is 20-23 but not all equipment works to the limits)

Next thing I'd look at is grounding. Actually measure the telco protector ground and verify it is not open (sometimes that solid wire breaks and you cannot spot it.

Also look at the grounding of the PBX.

You can get weird stuff if there is a noisy or floating ground.

Best of luck.

 

[skinswin]

Skip555,

If we push the button on the phone set, as soon as it looks as if the hold is dropped we can sometimes save the call. If we wait 2-3 seconds after the "arrow" disappears on the handset, then no luck. Do you remember what timers you adjusted?
We don't use VOIP? We're the government...that's too high tech for us!! haha
It happens with multiple line, multiple extensions, multiple sets. It happens with 1 line occupied through all of them being occupied.

ISDNman:
Ground loop current was 40mA, we've played with it from 20-40mA. I'm going to look again at the grounding. I'll also check the telco protector ground.

We are on an UPS. W

 

[skip555]

If we push the button on the phone set, as soon as it looks as if the hold is dropped we can sometimes save the call.

well whats happening is the system is dropping the call the Dialtone provider is treating the mometary drop like a flash and not disconnecting instantly

the fact that the call is still there reinforces the fact that its nothing from the CO or cabling.

I agree improper grounding can cause wierd problems but it still seems to me that if it where the case you should be dropping calls in progress and not just on hold.

Ive worked on some norstar but never the BCM , my recolction is that there is not much in the way of system timers on norstar that the installer can accsess

The tie/ nitusko / NEC line does have a lot of installer adjustable timers I just counted the ds 2000 I have 26 trunk timers to play with .

anyway the best I can recall it was far end disconnect , I could set it high enough to stop from dropping calls but then it didnt disconnect on calls that where over, keeping the line "hung up ".

it was quite awhile back and I dont recall all the specfics but I do remeber spending lots of non billable warranty hours getting it working right

 

[skinswin]

Skip555,

I understand what your saying. It makes sense to me, but I'm just trying to figure out why 5 different Nortel systems, and I just found this out also, before my arrival there was a Comdial unit that also had the same problem.

It's definitely getting to be frustrating since I'm not a telecomm guy. I'm just fortunate enough to be selected to try and fix it. Lucky me!...

Thanks so much for the help.

JEff

 

[ISDNman]

These are analog trunks, right? Loopstart or Groundstart?

Measuring at the trunk, is the loop current the same when a call is on hold as it is off-hook?

If you put an analog phone on one of these trunks, what happens if you do a very fast flash (e.g. hit the hook switch very rapidly?)?

There are timers at the CO too that should ignore brief tansients. It is possible (but not very likely) these are set wrong.

At least with some equipment there may be a very breif interruption in loop current when placing a call on hold or off taking it off hold. The CO is supposed to ingore these teransients, but perhaps in this case it does not.

 

[skinswin]

ISDNMan,

Analog Trunks, As far as Loopstart or Groundstart, I'm not sure what that is or how to check.

I'll check the current levels first thing tomorrow. I have to take care of my real job for the rest of today. Thanks to you and Skip555 for all your help.

Please check back tomorrow morning to see the updates.

Thanks again to all for the help.

Jeff

 

[skinswin]

Okay, Here we go....
It is a loopstart system.

The current levels at the trunk and when placing a call on hold do not vary or drop at all.

Thanks for the help.

Jeff

 

[ISDNman]

Did you use an analog or digital meter. Hard to see breif tansients on a digital meter.

If the loop current does nto vary when you place a call on hold then it pretty much *can't* be the Telco. All it knows is whether current is flowing, as someone else has pointed out.

What about the station side of the PBX. Are the proprietary sets or are the analog sets? If thse are analog sets then the same group of questiosn apply on the nalog side.

Good luck

 

[skinswin]

ISDNMan,

Used an analog meter looking for any type of deflection.

The telephone sets are Norstar Meridian 7310 digital phones. Is that what info you were looking for?

Thanks,

Jeff