sundance-communications.com/forum Forums TDM Business Telephone Systems Mitel Telephones & Systems SX-200 Digital Dropping inbound calls

I'm working with a 480 port SX-200 Digital that is said to drop 4 or 5 inbound calls per day for the past few months. The T1 provider hasn't changed in several years, and has already "performed testing" and ruled out any issues on their end, according to the owner.

I am a data guy just getting into the phone side, and have completed SX-200 ICP training. I used the link off of this site to obtain the manual for this unit, and it doesn't appear to function much differently than the ICP that I was trained on.

That said, I had planned to look at the system ground, and check the maintenance logs for anything obvious. The manual also made mention of the disconnect timing allowing for periodic loop disconnects during call processing from the CO, though I'm not sure how to verify that this is the cause of the issue.

Any additional suggestions would be greatly appreciated.

System ground would probably have made much more trouble, long before now.

Maintenance logs will tell you if specific hardware detects a fault, but won't really let you see what happened to specific calls. A peg count would be a better diagnostic tool.

When you say 200 Digital... Is this the 672, that looks like a small refrigerator, or is this the Digital Light, which looks like a set of "mid-tower" PCs? Or is it an ML/EL, which looks like a small microwave oven?

Also, I've discovered that folks are much more helpful around here if you supply an email address and/or website in your profile. Just a hint.

This is the SX-200 Digital 480 port configuration - looks like a refrigerator. Bay 3 - the top bay is all analog.

Thanks for the tip - added e-mail to my profile.

Okay, the first thing to note is that this is an older system, probably circa 1988-90 or so, and it may just be showing its age.

Also, those units were notorious for overheating. Chances are, both front and rear doors are propped open, and there's an oscillating table fan stuck in the door -- right? So you could have a heat issue.

I would suggest being as subtle as possible, but hinting to the customer that they need to start planning for what they will do next for telephones. Especially if this is the one that backs up the db onto 5 1/4 floppies.

For the immediate problem, I recommend logging in under maintenance (unlike the ICP, you can't jump laterally from CDE), and going to TRAFFIC_MEAS (F5). If traffic measurement has been set up, PRINT will give you the most recent peg count report. Your ICP manual should help you decode the report.

Also, if you can trace the problem to specific trunks or trunk groups, you can busy out specific trunks (Maintenance, 3, 0, 3) and Return-to-service (3,0,8) for troubleshooting. This may help you isolate a problem channel or problem LS/GS trunk.

This assumes that you've already done some basic testing of your LS/GS trunks, like hooking up your buttset and testing for dialtone, call completion outbound, calling from your cell phone for call completion inbound, clean 2-way voice path, etc., -- A faulty LS trunk can be a cause of intermittent problems, especially if you're way the heck-and-gone out in the boondocks.

Strongly recommend suggesting (nicely) that it might be time to think about when to schedule the next upgrade for the system. Mitel does have remarkable reliability, but nothing lasts forever.

BTW, just to give yourself some peace of mind, print out your database using CDE form 32. It will save you a lot of bad words should there be a catastrophic failure.

Personally, I use my laptop, and set ProComm to data capture, hook it to the printer port (found inside the top back door, near where the amphenol cables hook up), and then log in at the console to print. It gives me a nice soft copy, easy to print, and saves carrying around a dot-matrix printer.

Sorry to be so long-winded. Hope some of that helps.

Many thanks for sharing your insight.

The only thing I can add is.
If this is a digital T-1 meaning it is terminated on a t-1 trunk card. I usually look into the Maint side and do a Reports-Show-Status= bay slot circuit of your T-1 card and once the ports show up on the screen press 3 for Link Status. top right will show you your Sync= to the carrier. Bottom right of center you will need to look for Source= should be your bay slot circuit of T-1. And make sure you are in AUTO not FREE. Also look at the DAC at the bottom of the page, the DAC is the clock source timing in HEX 7FF is a perfect clock but unless your system is located next to the central office you will not get 7FF. If per chance you do have 7FF I would look at your clock routes. You can also look at the right column of that page for TXyellow and BPV. If you have those with a yes I would research the link dropping. Oh you can also look at Reports-Show-alarms-Device type-T-1 and on the right column you should read " long term active " anything else and you are looking at clocking agian. Hope this helps, good luck.

It is a T1 that terminates into a T1 Trunk card. Thanks for your input, Alex - much appreciated.

Well...went out to the site today to evaluate the issue. The problem actually happened to me on the drive in when I called to let them know I'm on my way - rang 2 times, then it dropped.

At the site, I discovered that the hotel has an Adtran device that takes the T1 into analog trunks - the supposed T1 card was the digital interface card. Looked through peg reports, watched several live calls, saw nothing at all wrong. I did note that an inbound call from my cell phone took about 2 rings before the Adtran device turned it over to the Mitel Trunk Card - same number of rings I got before my call dropped. I became more suspicious of the Adtran device having timing issues, and had the CLEC open a trouble ticket.

Fingers are crossed...

-=Mike

I'm going to tend to agree that the Ad-Tran is suspicious. What is the Ad-Tran doing? Is it splitting off data channels, or is it a channel-bank simulating analog trunks?

Telephoneguy - I somehow missed your last post unitl went to add to the topic just now. It is a channel bank splitting off analog trunks.

The CLEC came out to the site to follow up on that trouble ticket, and downgraded the firmware on the Adtran channel bank stating that they had seen this issue before. The issue remains unresolved.

-=Mike