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EHDU - GSM to BRI

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danramirez

Programmer
Oct 25, 2009
1,136
ES
Hi,

System is 3300 running MCD 4.1.

We recently connected 2 "GSM-BRI gateways" to a 3300 using QuadBRI MMC. Each of those gateways are two-channel gateways which give 4 trunks from the PBX to the GSM network.

GSM-BRI gateways are manufactured by provider in the UK called Telecom FM. w_w_w_telecomfm_co_uk. GSM provider is Vodafone in Spain.

Each GSM Channel has its own Mobile number, and the four of them have been grouped together under a Pilot Number. I guess they have created sort of a Hunt Group on their side.

The reason of doing all this is because our customer has contracted with Vodafone flat rate between all its corporate mobile phones. So... when any of the employees call the pilot number from its mobile phone the pay no extra charge, as this is considered an "internal call" between corporate cell phones.

In the past we had it set up that: any calls received over these BRI trunks were answered by the auto attendant, so the caller would dial any internal extension and be connected with no problem.

We wanted to extend this so the mobile caller would call the pilot number, and then dial 9 to make local calls, international calls etc. As rates from PBX are a lot cheaper than what Vodafone charges.

So... EHDU would be the choice, as once the mobile caller dials in, he/she would be recognized by the PBX and grant access to features, ARS, etc.

So... It works partially. When the mobile caller calls each individual number of the GSM, you hear ring back tone (only one ring) and then flat dial tone. Then you dial nine to make outside calls, or dial feature acces code for paging, etc. and everything works perfectly. You can even program address book entries in a smarmphone (Blacberry) with a pause in between the mobile number and the extension, and it works as it should.

The problem is: If you dial the Pilot Number (Which is a better option as it will always connect you to the first available GSM Channel)it gives you ring back tone, then you hear the flat dial tone but it doesn't take any DTMF you enter from your cell phone. Note that the ring back tone you hear this time is different from the one when dialing straight to a number. It looks like you get 2 ring ring backs as the hunt group is looking for the first available channel...

The thing is... you are not able to dial DTMF when calling to the pilot number as an EUDH.

Any ideas why it doens't work when calling as an EHDU but it works when the answering point is the A. Attendant?

Any ideas what to do?

I haven't called the GSM provider yet. They also provided the GSM gateways.

I have tested this with PRI trunks and it works with no issues, the problem with the GSM is that there are too many things involved in the call. The hunt group by the GSM provider, The GSM-BRI Gateways, and the 3300...

I would appreciate your comments/suggestions.

Regards,

Daniel



 
Is the answer point for the BRI trunks the hotdesk answer point?
Is CRS enabled in the trunk service of the BRI trunks?

A CCS trace would helpful to debug. You should see something like:

ISRM
NAM
CCM (At this point you should hear dialtone and DTMF can be received).

If you only get to NAM it is possible to hear Dialtone and not be able to DTMF.


Regards,
Ken
 
Thanks Ken,

Yes, the answer point for the BRI Trunks is the "Hot Desking Access Number" set in System Access Points.

Call Recognition Service is set to "Trusted". Shal I try Trusted FOPBX?? Not sure what this last valu es usefull for...

I will take CCS captures and see what I get from there.

I'll comment further once CCS traces taken.

Regards,

Daniel
 
Ken,

SORTED!!

CCS trace was the key to determine the problem.

CCM signal appears after a couple of seconds than the call has been received by the GSM Gateway. Once CCM is on the CCS Trace one is able to DTMF successfuly. So.... What I did was introducing Three PAUSES on their mobile phones telephone directory for every call they do throug this array.

Thanks for that!! regards,

Daniel
 
Daniel,

I am curious, how much of a delay was there between the NAM and CCM.

Thanks,
Ken
 
Ken,

Two interesting figures:

-There are about 12 seconds, since users press the SEND key on their mobile until they hear dial tone from the External Hot Desk Answer Point. That is too much time from my point of view. Bear in mind that we have the GSM delay, the Vodafone Hunt Group identifyin which GSM channel is available, the GSM-BRI Gateway delay, and finally the PBX processing the call. I know the PBX is quick but by adding all delays we get to about 12 seconds.

12 Seconds sound too much for me but not for them... they are saving too much money by calling through the Mitel system. They pay no extra charge when calling from their cell phones to the GSM gateways, and then they can reach an extension overseas at no Long Distance cost. Their PBXs are clustered!!


-The NAM CCM delay is about 1 or 2 seconds.

Thanks very much again, Regards,
Daniel
 
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