Disclosed is a system whereby in a transmit mode analog speech is sampled d converted digitally to 12 bits of accuracy and then fed into a fast Fourier transform (FFT) processor which analyzes the speech into spectral and pitch parameters. These parameters are then quantized into a data stream which...http://www.google.es/patents/US4310721?utm_source=gb-gplus-sharePatente US4310721 - Half duplex integral vocoder modem system
