METHODS AND APPARATUS FOR ENCODING AND DECODING DATA TRANSMITTED OVER TELEPHONE LINES

A method of generation and detection of acoustic signals carrying alpha-numeric data for reducing the effects of noise and thereby improving signal transmission without the need to boost the power of the signal. In accordance with one aspect of the invention, a special DTMF acoustic signal consisting of a combination of two frequencies will be generated for the representation of a particular alpha-numeric character that will be similar to the standard DTMF tone. The difference between the amplitudes of both frequencies varies during the time of generation of the DTMF tone in such a way that both signals will arrive at a final destination detector, i.e., an interactive voice response board, at least for a portion of the generation time, at a relatively similar amplitude, thereby substantially increasing the probabilities of being recognized as a DTMF signal.