Call Manager Express (FXO) Cons over BRI in UK

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Oct 23rd, 2007
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Hi, it looks likely I'll be installing a CME UC500 I'm looking for advice.

My customer currently has 3 FXO connected into his old PBX, generally I only use ISDN 2 with CME. What if any are the drawbacks of using FXO and not ISDN with CME? Will I still be able to use all the features of CME specifically music on hold and IVR, Hunt and Pickup groups etc? I also plan on using a SIP gateway to provide an additional line and to perform leased cost routing, would this be a problem with the UC 500?

In addition does anyone have relevant configuration examples for the UC 500 FXO model and BRI model?

Many thanks,


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Overall Rating: 4.5 (2 ratings)
paolo bevilacqua Wed, 10/24/2007 - 02:30
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You have many disadvantages using FXO Vs. BRI.

First and foremost, you are exposed to "disconnect supervision" problem, especially when using CUE, that causes you line/port to remain stuck.

Second you loose the digital quality of voice, suffer longer setup an answer times, loss of DID and CLID features, much harder to diagnose, etc.

So it's recommended that you stay with BRI as long as possible. I really don't think that a $5000+ IP based phone system deserves anything less than a digital connection to PSTN. Take it this way, FXO would be the weak link of the chain.

Hope this helps, please rate post if it does!

davieshuw Wed, 10/24/2007 - 07:18
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I agree corb, the money he must be paying for the 3 lines.. may as well get a BRI installed. The job will be much easier, for him and you!

BT charged me £119.50 to install my ISDN 2 and theres a £46.50 monthly charge for rental, which, when he's buying a UC520, is peanuts. Jut tell him he has to have ISDN :)

paolo bevilacqua Wed, 10/24/2007 - 08:01
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There is to say, one should hurry in getting ISDN BRI as long is offered in the UK.

I've heard plans of BT of discontinuing the offer.

Very unclear what the would offer as substitute!

mamadubig Tue, 11/13/2007 - 10:40
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Anyone knows where I can find configuration examples for the UC520? Any links would be appreciated. Thanks, Mohamed

paolo bevilacqua Tue, 11/13/2007 - 10:42
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There is nothing special. Configure "comand-type a-law" under voice, ports, the rest depends on how do you want to dial out (with 0 or not,) etc.

AJAZ NAWAZ Tue, 11/13/2007 - 12:01
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Nice to meet you.

I have done some extensive searching on this set of products and have to say there is limited information at the momment on this device. That said I can share with you the two worthwhile links for this product:

and, <-- this link is not affliated with Cisco but looks really good.

hth, all the best.


mamadubig Tue, 11/13/2007 - 18:01
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Nice to meet you too Ajaz. Thank you Paolo and Ajaz for the help. This forum has always provided answers for. Thanks to all.


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