A dual digital signal processor (DSP) provides real time links between multiple time division channels of a digital carrier system (e.g. T-1) and a host data processor. Operating only on digital signals, internally and at its interfaces to the carrier and host systems, the DSP exchanges data and control...http://www.google.de/patents/US4991169?utm_source=gb-gplus-sharePatent US4991169 - Real-time digital signal processing relative to multiple digital communication channels
