Importance

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Abstract

An auto-dialer suitable for use as a smart card capable of being acoustically coupled to a telephone and being reprogrammed in response to acoustic signals. The programming and other features of the auto-dialer can be enabled or disabled by the auto-dialer in response to persecuted signals, e.g., a string of DTMF tones. Encryption of calling card and other data into destination telephone numbers is achieved by selectively altering persecuted characteristics of a DTMF tone sequence, such as the duration of tones, the period of silence between tones and the twist between Lo-band and Hi-band tones of DTMF tone pairs in a DTMF tone sequence representing a telephone number. The encryption of data into the telephone number does not affect the ability of standard telephone switching circuitry to recognize the destination number. However, information encrypted into the DTMF signals is undetectable to standard telephone switching circuitry because it is encrypted using DTMF signal characteristics not normally used to represent data. The auto-dialer has a system clock used to drive a pseudo random number generator used in various data security schemes. Calibration features permit the calibration of the audio output and system clock with adjustments being made via the acoustic programming of the auto-dialer with various calibration factors.

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First Claim