atcomsystems.ca/forum Forums TDM Business Telephone Systems Mitel Telephones & Systems LS/GS hybrid mode?

I've been trying to get up to speed on telephony basics. In particular as it relates to the equipment my company is currently using. Our main system is an old SX200 analogue (the microwave looking one). I haven't really found a lot of good info on the workings and functions of the various cards and options for these models so I'm muddling through the best I can.

One of the resources I've found is Lee Goeller's website which, at least IMO, is a great resource. Especially if you want to start from the beginning and not jump right in with the current state of the art equipment, but want to learn how we got to that point.

After reading Lee's "The PBX: What It Is, How It Works." series, I've really learned a lot, especially stuff that's relevant to our old SX200 and antiquated telco.

Reading about outgoing CO and Tie calls got me wondering about something. In general (and in particular on the SX200), does an LS/GS card work in either Loop Start or Ground Start mode, or does that also mean that they can operate in both modes? What I mean is, does the card work in one mode for incoming calls and the other for outgoing? Is there some other hybrid mode or combination of LS/GS or is it always one or the other?

The reason I came up with this question is that I've been testing intercepting calls from our SX200 before they hit the CO.
Running in KewlStart mode, the channel bank answers the SX200 just fine, and can route those calls over VoIP channels beautifully. However, if they are local calls and I try and dial out on the CO lines to pass them through, I lose the first digit dialled and the line seems to hang. This seems to fit with the description of the problems that Ground Start is intended to solve. I intend to try switching the FXO ports to GS mode and see if that makes a difference, but I wanted to hear what the experts say about this, and if anyone knew of some sort of hybrid LS/GS operation.

My other thought was that the SX200 was detecting the mode (KewlStart) of the channel bank and adjusting itself to it.
This would also explain why one side of this setup works and not the other.

Anyway, I'll keep reading and testing and hopefully figure it out. I was just really interested in hearing from anyone that had any thoughts on this. So far I'm finding my telephony crash course tough, challenging, and very interesting. It's a totally different world from I.T. and is pushing my old brain to think differently. I'm sure this is a good thing. ;')

On each CO trunk card, there is a LS/GS set of pins to choose which type.

The trunks need to be configured the same on both sides, PBX and Channel Bank, to work properly. Is there a problem with the current operation?

On the old 200 analog there are actually slide switches that dictate whether the circuit on the card is treated as loop or ground. Loop or ground does not really affect inbound (as far as being able to ring the PBX) it does however affect whether or not the PBx can seize dial tone when trying to originate a call. If you have a GS trunk and the card circuit is set to loop (or vice-versa) you will not be able to pull dial tone on the trunk from the CO and the outbound caller will receive dead air.


The SX 200 cannot automatically "detect" anything. If you have a switch on a CO card set to GS then the PBX will try to apply ground to the trunk (if you do not have a good ground to the PBX it will fail to pull dial tone). If the circuit is set to loop start it will just act like your phone at home and come off hook to pull dial tone.

Since your your Mitel seems to be having problems, and since it was most likely installed originally with G/S trunks, you'll probably need to pull the trunk cards and set them to L/S. It's really not hard to do, IF you have the book, and know which ones need to be changed! The one that shows the trunk cards, 3 different models, 111, most often seen 211, and seldom seen 311. They have line drawings of the cards with switch call-outs. Oh, this part you'll like. Any card with BLACK pulls can be removed when the system is running. Mitel says it's ok, it won't hurt the system. It MAY knock down a call in progress, but heck with 'em if they can't take a joke. DON'T PULL ANY OTHER CARDS WHILE THE SYSTEM IS ON!!!!! John C.

lightninghorse... Yeah, the telco guy told me that before, we had a problem with a trunk and he told me to go pull the card and put it back in to reset it without having to reset the whole system. I asked twice if he was sure since I couldn't believe it. ;')

Where can I find the info on these cards and the switch settings?

However, for this problem, I'm not having trouble with the Mitel. It's talking to the channel bank nicely. It's the CO lines that the Mitel _was_ talking to that I'm having trouble with.
Now that I know that there's no hybrid mode or autodetect on the LS/GS cards, I'm wondering what the issue is getting calls out on the CO lines. I'm not too worried yet as I haven't really done any testing or monkeying with this yet. I just wanted to get some background before I started that process.
Now that I am fairly sure the CO lines aren't setup GS (since the Mitel that was talking to them talks fine to my channel bank which is configured for KewlStart, which is essentially LS) I'm now thinking I just need to run FXO tune to get my channel bank's FXO ports matched to my CO lines. I'm using an Astribank XR0010 BTW. It's connected to an Asterisk box. The whole purpose is to sit between the Mitel PBX and the CO Dial Out lines and intercept long distance calls and route them out VoIP. This part works great BTW. The second part is to route local calls out the FXO ports to the CO lines.

The Astribank is able to talk to our other standard B1 lines just fine using KewlStart so I'm thinking I'm missing something with regards to setting up the CO/DO lines.

Thanks for all the good feedback.

Oh, BTW, our LS/GS cards are 9109-011-001-SA models.
I'm not sure how this relates to the 111/211/311 numbers that Lightninghorse mentioned.

I'd love to know a source for documentation on these and the SX200 in general. I've been all through the net and Mitel's site and found a few things. But none of the detailed stuff I'd like to see. The kind of manuals a tech would use to set these up.

This is frustrating because I was able to download every kind of manual and spec you could imagine for our little Nortel at one of our other buildings.

The 9109-011-001-SA is a analog trunk card for the sx200 digatal sx200light sx 200 el/ml & can be used with the sx200icp pbxs

As TDS pointed out, your trunk card indicates a "Digital" system. With Jumpers, not switches. Not sure where I drew the conclusion you had an old analog SX200. Does it run on 5 1/4 or 3 1/2 floppies. Either in a cabinet resembling a clothes washer, or multiple cabinets resembling computer towers. Or does it have a flash card, with cabinets that resemble Microwaves? John C.

Since he's calling it a refridgerator model, it has to be a digital or combo. The card part is definitely a digital though.