Multiplex-vocoder for voice response

Voice response systems based on vocoders have the advantage of a large vocabulary, but they are expensive, since conventional vocoders cannot be multiplexed due to the energy stored in their resonance circuits. This drawback has been overcome by our new "megahertz-vocoder" which has formant circuits tuned to frequencies 512 times higher than natural. Short segments of speech are synthesized in 1/512 real time and stretched in time afterwards by means of an analog shift register. Since the vocoder is used only 1/512 of time it can synthesize speech for several hundred different channels. The software necessary to control the megahertz-vocoder is the same as that for the standard one.