1.1 Overview
To digitally process telephone calls, the PBX must use a certain number of DSP (Digital Signal Processing) resources.
DSP resources are provided by the DSP cards installed in the PBX.
Since the DSP resources are limited, no further operations (e.g., telephone calls, playing an OGM) can be
performed if all resources are in use.
The following basic operations require DSP resources.
• IP extension call (To Trunk)
• IP trunk call (To Ext)
Calls via IP-CS (Does not support P2P)
• Conferencing
• Accessing the Unified Messaging system (including recording calls)
• OGM playback
• Echo canceller (for trunk-to-trunk analogue calls)
Note.
For IP Ext/Trunk calls, the required DSP resource depends on the codec (Compression) used (G.711 or G.729) .
The Higher the Compression (G.729), the more DSP resource is required (but less Bandwidth)
The Lower the Compression (G711), the less DSP resource is required (but more Bandwidth)
P2P Calls (within the same P2P Group) can be considered NOT to use DSP resources.
DSP Resources are not ‘shared’ between Master/Slave systems – Calculate Resources for each PBX individually.
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