UC500 max Conferences on PVDM2-64 and 7945G

Unanswered Question
Jul 18th, 2009

I have a question I would like to clarify.

I'm working with a UC500 system for 24 users max. The customer would like to cut some conferencing cost and host the conferences locally by utilizing the new UC500 that will replace the current PBX. Currently, they are going out to one of those 800 Bridges provided by ATT. Somewhere along the line (sales process) the customer hear from someone that they could host conference calls with up to 20 participants either via Ad-hoc, or Join feature to single line on a 7945. Customer has an ISDN PRI and PVDM2-64.

Is this possible? The max Dn's I'm sure is 8 (Octo-line) and cannot be overlaid. So the max number of parties in a single conference is 8. Is this correct?

I know the PVDM2-64 will be able to do it as referenced below, however, I don't think the IP Phone can't do more than 8 on a single number/line.

This is the response I had from the partner helpline.

Thank you for contacting Partner Helpline Presales Support.

UC500 supports hardware configuration for 4 different user density: 8U, 16U, 32U and 48U. The 8U and 16U density models are shipped with PVDM2-32, whereas the 32U and 48U models are shipped with PVDM2-64. PVDM2-32 has 2 DSPs and PVDM2-64 has 4 DSPs. Without getting into too much technical details, let me just say that each DSP has 240 credits and g711 calls take 15 credit for each call, whereas g729 calls take 30 credits. Based on these credits, each DSP can support upto 16 g711 calls or upto 8 g729 calls or a mix of those.


Any help is appreciated.


I have this problem too.
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rob.huffman Sun, 07/19/2009 - 09:05

Hi Armando,

I agree with your assessment here :)

Q. Does the Cisco Unified Communications 500 Series support hardware conferencing?

A. Yes. All Cisco Unified Communications 500 Series configurations support hardware conferencing, allowing up to 8-party conference and Meet-Me Conferencing features.

From this excellent Q&A doc;


Hope this helps!


PS:even if this was supported the whole PRI would be chewed up hosting a 20 party conference, which would be a poor plan I think.

aramos17428 Sun, 07/19/2009 - 09:19


Thanks for your time. The conference idea is supposed to be taking place one time maybe once a month. Customer knows about the number of channels (PRI) and possible results if they are all in use by conferencing (design). I just wanted to confirm since the idea was sold to them by Cisco (according to what they told me, however, we all know that sometimes customers mis-understand some features and their capabilities) and now I have to go back and tell them sorry but you can not have your conference call and just wanted to make sure there is not way do to this (except with full CallManager version Up to 200 calls per device).




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