Panasonic KX-NS5110, A DSP card is a digital signal processor card with DSP resources that can be used for VoIP calls, Conferences, the Unified Messaging feature (Voice-Mail and Auto Attendant), and the DISA/OGM feature. The DSP cards are compliant with ITU-T G.729A and G.711 codec methods. Depending on the amount of your DSP resource needs, DSP S, DSP M, or DSP L cards can be installed. The number of resources provided by each type of DSP card is as follows: DSP S card: 63 DSP M card: 127 DSP L card: 254