ELECTRICAL AND ELECTRONIC APPARATUS AND INSTRUMENTS FOR USE IN THE COMMUNICATION FIELD NAMELY NOISE SUPPRESSORS, STATIC AND DYNAMIC DISTORTION ELIMINATORS, EXPANDERS, COMPRESSORS, ERROR CORRECTORS, LOUD-SPEAKER SCRATCH REDUCERS, AND FILTERS; DATA TRANSMITTERS AND PROCESSORS; DATAPROCESSING PROGRAMS; MODULATORS, DEMODULATORS, ENCODERS, DECORDERS, REGENERATORS, SIGNAL PROCESSORS, EXPANDERS