When are DSP`s needed

Unanswered Question
May 21st, 2009

I have SRST site about to be installed back to a central CCM.

The handsets are new-ish 79x1- So transcode themselves? G729 and G711

1. Do I need local DSP`s ?

2. Are they needed for conferencing, across the WAN if I set the region, Locations to G729

3. If the sites goes into SRST again do I need DSP for conferencing or anything else


I have this problem too.
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Jaime Valencia Thu, 05/21/2009 - 08:07

1 If you're going to have a PRI yes, you need DSPs for voice termination.

If you're just going to call between phones no.

2 Yes, SW CFB only accepts G711 so you need either XCODER or HW CFB to use G729

3 Same as 1



if this helps, please rate

Nicholas Matthews Thu, 05/21/2009 - 09:49

You need DSPs in these situations (this has been asked many times, you may want to try the search function)

1. Analog ports are involved. T1 CAS, PRI, FXO, FXS.

2. Hardware Conferencing, transcoding, or a hardware MTP is required.

Transcoding is only required if 2 endpoints do not share any capabilities. If you tell your remote phones they can only do G729, this isn't a problem as long as every device they want to communicate with also can do G729. But if you have something like CUE which only does G711, you then need a transcoder. Generally IVRs and other applications don't support G.729, although I think Unity is the exception.

The SRST site will need DSPs because your PSTN connectivity (PRI, FXO) will require it.

Use the DSP calculator to find out the details:





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