atcomsystems.ca/forum Forums TDM Business Telephone Systems Mitel Telephones & Systems Mitel SX 200 ground start problem

Recently our local CO installed a new Lucent Technologies CO switch.I think he called it an EMS. Now with this new CO we are having
problems with our Mitel SX-200
ground start lines. Seems the SX-200 doesnt hold the ground start long
enough for the new CO to
recognize a call for dial tone. The SX-200 will pull a dial tone
about 30 percent of the time. I can start these lines manually with a momentary connection to ground. I dont
see that the ground start duration can be lengthened in the system programming options. I dont know if there is an adjustment on the trunk card itself. These are 9110-211-000 Transformer 4circuit trunk cards.
Nothing is mentioned in the manuals on ground start timing. Looking at the trunk card. there is the groundstart/loopstart switch, 4 dip switches, the busy switches and a potentiometer.

I have two identical systems at different locations . Both are behaving the same way since the new Bell CO was installed in town. Im told it is an EMS? Lucent Technologies Switch. From my end, a solution might be to add a few milliseconds to the ground start duration on the MITEL. Its acting like it's on the verge of being too short.Like I say, it only pulls a dial tone 30 percent of the time.
And I can start them manually.
I
hope the CO can make some
sort of accomodation although their Bell repair tech told me that there arent any adjustments they can make on their end. Anybody run into this kind of a problem on a newer Lucent Technologies CO?
Would appreciate hearing what you
were able to do about it.

when I ground start the line and pull a dial tone I measure 8 volts across ring and tip with a 15 ma current flow. ( current meter in series with the test set is about 20ma) (current meter in series with the Mitel PBX is 15ma)
Ground start or wink current is barely 20ma then drops to 15 ma at dial tone @ 7.9 volts across L1 L2. Is this current within spec?

Also, other measurements with system connected: (Mitel system kicks out 5.5 volts across the line) Im told this is normal.
measurement between ground and L1=47.2 volts
measurement between ground and L2=52.8 volts
I never measured these parameters on the old reliable CO.
Thanks for any help or advise.

Try reversing the polarity of the trunks and see what happens. Your problem may be due to reversed polarity on the trunks during the CO cutover. I know that this is a stretch, but it's worth a try.

Soft switches are causing problems all over the place since most major carriers are using them in an effort to save money. They cost less to operate and take up less space, but they don't provide "real" telco-quality lines. The telco employees don't know how to manage/fix them either.

Ev has a point and it is worth a try but it wouldn't explain pulling dial tone some of the time (on the same trunk - have you accessed each one individually from the console or test line). And ususally with the old SX 200 if you have the polarity reversed you get the trunks ringing in at the console.

I know there are ten dip switches on the trunk card but don't have the manual anymore for those - however I think there may be an impedance switch among those and maybe that might make a difference. - Another long shot.

Could be a problem with grounding if old COs were more tolerant of a weak ground. Measure the resistance between the approved building ground and your PBX ground... should be less than 5 ohms. And just for S&G, test the CO ground and the resistance between your PBX and the CO ground. It's just possible the Telco isn't perfect

Thanks Ed;,
As you said, after the CO cut over, the polarity was reversed, so that was the first thing I tried. It is polarity sensitive as you say and only works one way.

The lines are ringing in fine for incoming calls to their designated stations as they should. Just cant access a dial tone for outgoing
most of the time.

Yes, Harry, Thankyou, I will check for a weak grou nd and let you all know. good to know about that less than 5 ohms. Ill check that next. Thankyou.

Yes;,re: the dip switches on the trunk card, they arent really elaborated on in the manual ,just indicated, . Thankyou,I tryed altering them and it didnt seem to alter the behavior in any. I should give them another go after checking for
weak ground if the ground isnt it. Many thanks to you all.

As I recall, Re the dip switches,
10 of them are busy switches on the end of the board
with the leds., then on the board proper are two dips for each line that may be impedence related.Ill look again in the manual, see if I can make more sense out of the picture. It does say HIGH for one of the positions. I cant recall the other switch. When I go for lunch I will look again. Thanks

There are 8 switches on the edge of the card. 4 to busy out incoming, 4 to busy out outgoing. There are 10 dip switches on the card, 4 to set 3rd wire operation, 1 to ignore reversals, one to set release time and the other 4 or not used. There are Hi-Z switches on the individual trunk modules, 2 per mod. They are the 2 switch dip switches, one switch for each trunk, the HI-Z appears to be the one closest to the outer edge.

I never seen this problem, ground starts are usually reversed polarity or a bad ground. I didn't see anywhere in programming to adjust ground application time. Have you considered switching to loop?

On the mother board of the 9110-211, you have a row of 10 DIPs that control functions of the card overall. 1-4 control the 3rd wire condition for Trunks 1-4, 5 controls the "Ignore Reversals" function, 6&8 control Release Time, and 7,9,&10 aren't used on the 211 card. I don't think any of these should be a factor in drawing dial tone.

On the daughter boards you'll see two pairs of DIPS. These set the XT control and the Hi-Z; since you're in Canada these should be set to 'Closed' per the manual. I don't think either of these would interfere with dial tone, though.

Good Luck,

Thankyou for all the info on the board switches.
Ill have to keep that on file. I checked for weak
ground and no its okay. Less than 1 ohm. And both systems at two diffrent locations .5 mile apart are behaving the same. One other thought that occurred to me was the fact that the old CO was located 10 miles away and and the MITEL system pulled a dialtone from it just fine. I remember them being amazed when it was first connected. Now Im wondering if due to the long run (10+ miles) might they have added supplemental
capacity to counteract the length of the run? Now with the new switch located so close. less than 1 mile away, maybe the added capacity (if it was ever added) wasnt removed. I dont know, might this be a possibility? Ill call them tomorrow.

Thankyou for all who responded
We would use loop start lines instead of ground start except these lines are used for remote access "dial in" and the Mitel wont do a loop to loop connection. I tried that initially and thats why we ordered the ground start lines when the system was initially installed. We couldnt make the "remote access dial in" feature work with a loop start line. A old timer Mitel tech tipped us
off on that one as it wasnt mentioned in the manual either that it wouldnt do a loop to loop connection. .Took us days of trying till he gave us that tip. So thats why we ordered the ground start in the first place. Now Im wondering about an outboard converter. Ground start to loop converter if such an animal is available. then we could use loop lines.

One other question. What about the line current? Does 15ma seem acceptable to you guys? when I ground start the line and pull a dial tone I measure 8 volts across ring and tip with a 15 ma current flow. ( current meter in series with the test set is about 20ma) (current meter in series with the Mitel PBX is 15ma)
Ground start or wink current is barely 20ma then drops to 15 ma at dial tone @ 7.9 volts across L1 L2. Is this current within reason?