The designer can leave the decision to use either a HW block or implement the function in SW until other systems decisions have been solidified. Each codec connects through analog circuitry to a telephone line interface on one side and to a microphone and a loudspeaker on the other side. Digital Section In Figure 1.a , the basic structure of the system consists of two echo cancelers and a soft echo suppresser mechanism as shown. The microphone and line VOXs determine at which SNR level the corresponding VOX will trigger. These amplifiers must have a flat frequency response in the codec's bandwidth, while A1 and A3 must provide enough amplification of the input signal so that the dynamic range of the codecs are correctly used.
Designers now have a means of producing creative, low cost solutions.
Through the use of the programmability of the core, designers can produce sophisticated adaptive filtering techniques to eliminate the changing noise sources which may interfere with proper circuit operation. Acknowledgment Special thanks to Alberto Bernstein, Voice Applications Manager, DSP Group, Inc., for the algorithm coding and development.