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New Member

IP Phone uses its own DSP???

I heard someone say that a 7940 or 7960 can perform DSP functions within itself so that no DSP modules are needed in the gateway for offnetting. I've never heard of a phone having its own G.729 or G.723 codecs. Is this true? Perhaps a new model of phone? I saw something where the 79x0-G phones are now on the market. Is this the codec thing?

Thanks, Jeff

New Member

Re: IP Phone uses its own DSP???

79x0-G is basically the same phone with icons on the buttons instead of words. G = Global.

The 79xx phones have codecs as do all digital phones. Since we can't hear 1's and 0's the phones have a codec to translate to analog for our ears. Whether you need DSPs is an 'it depends' scenario. Let's say you have two regions. One is configured to use G.729 while the other is set as G.711. The 79xx phones will adapt to the lowest common denominator.....which in this case is G.729. They also perform this function across the WAN so if both phones are G.711 but the WAN is G.729 the phones will use G.729 for that call across the WAN. So in this case the phones are accomodating the WAN so that you don't have to have the Gateway transcode on each side of the WAN. You still need DSP resources in GW to the PSTN though and you'll need transcoding (may be software) for conferencing and so on.....

The planning information for DSP resources is in the Call Manager System Guide and the Network Planning Guide on CCO.