System for carrying transparent digital data within an audio signal

Claim 1

A system for combining an unmodulated first analog signal and a digital signal, said system comprising: means for modulating said digital signal to a second analog signal different from said first analog signal; a first filter for attenuating, in a first frequency band, the amplitude of said second analog signal; a second filter for attenuating, in a second frequency band, the amplitude of said first analog signal, said first and second bands being nonoverlapping; means for combining said first and second filtered analog signals to form a single composite analog signal, a third filter for attenuating, in said second frequency band, the amplitude of said composite signal to extract said first analog signal; a fourth filter for attenuating, in said first frequency band, the amplitude of said composite signal to extract said second analog signal; means for demodulating said second analog signal to said digital signal; and wherein: said first band consists of frequencies below a -3 dB cutoff frequency, said second band consists of frequencies above said cutoff frequency, said first signal consists essentially of frequencies contained within said first band, and said second signal consists essentially of frequencies contained within said second band.

Claim 2

A system for combining an unmodulated first analog signal and a digital signal, said system comprising: means for modulating said digital signal to a second analog signal different from said first analog signal; a first filter for attenuating, in a first frequency band, the amplitude of said second analog signal; a second filter for attenuating, in a second frequency band, the amplitude of said first analog signal, said first and second bands being nonoverlapping; means for combining said first and second filtered analog signals to form a single composite analog signal, a third filter for attenuating, in said second frequency band, the amplitude of said composite signal to extract said first analog signal; a fourth filter for attenuating, in said first frequency band, the amplitude of said composite signal to extract said second analog signal; means for demodulating said second analog signal to said digital signal; and wherein: said first band consists of frequencies below a -3 dB cutoff frequency, said second band consists of frequencies above said cutoff frequency, said first signal consists essentially of frequencies contained within said first band, and said second signal consists essentially of frequencies contained within said second band.

Claim 4

A system for combining an unmodulated first analog signal and a digital signal, said system comprising: means for modulating said digital signal to a second analog signal different from said first analog signal; a first filter for attenuating, in a first frequency band, the amplitude of said second analog signal; a second filter for attenuating, in a second frequency band, the amplitude of said first analog signal, said first and second bands being nonoverlapping; means for combining said first and second filtered analog signals to form a single composite analog signal, a third filter for attenuating, in said second frequency band, the amplitude of said composite signal to extract said first analog signal; a fourth filter for attenuating, in said first frequency band, the amplitude of said composite signal to extract said second analog signal; and means for demodulating said second analog signal to said digital signal; and wherein said modulator and said demodulator utilize phase shift keying technology.

Claim 5

A system for combining an unmodulated first analog signal and a digital signal, said system comprising: means for modulating said digital signal to a second analog signal different from said first analog signal; a first filter for attenuating, in a first frequency band, the amplitude of said second analog signal; a second filter for attenuating, in a second frequency band, the amplitude of said first analog signal, said first and second bands being nonoverlapping; means for combining said first and second filtered analog signals to form a single composite analog signal, a third filter for attenuating, in said second frequency band, the amplitude of said composite signal to extract said first analog signal; a fourth filter for attenuating, in said first frequency band, the amplitude of said composite signal to extract said second analog signal; and means for demodulating said second analog signal to said digital signal; and wherein said modulator and said demodulator utilize phase shift keying technology.

Claim 6

A System for combining an unmodulated first analog signal and a digital signal, said system comprising: means for modulating said digital signal to a second analog signal different from said first analog signal; a first filter for attenuating in a first frequency band, the amplitude of said second analog signal; a second filter for attenuating, in a second frequency band, the amplitude of said first analog signal, said first and second bands being nonoverlapping; means for combining said first and second filtered analog signals to form a single composite analog signal, a third filter for attenuating, in said second frequency band, the amplitude of said composite signal to extract said first analog signal; a fourth filter for attenuating, in said first frequency band, the amplitude of said composite signal to extract said second analog signal; and means for demodulating said second analog signal to said digital signal; and wherein said modulator and said demodulator utilize quadrature phase shift keying technology.

Claim 7

A System for combining an unmodulated first analog signal and a digital signal, said system comprising: means for modulating said digital signal to a second analog signal different from said first analog signal; a first filter for attenuating in a first frequency band, the amplitude of said second analog signal; a second filter for attenuating, in a second frequency band, the amplitude of said first analog signal, said first and second bands being nonoverlapping; means for combining said first and second filtered analog signals to form a single composite analog signal, a third filter for attenuating, in said second frequency band, the amplitude of said composite signal to extract said first analog signal; a fourth filter for attenuating, in said first frequency band, the amplitude of said composite signal to extract said second analog signal; and means for demodulating said second analog signal to said digital signal; and wherein said modulator and said demodulator utilize quadrature phase shift keying technology.

Claim 8

A system for combining an unmodulated first analog signal and a digital signal, said system comprising: means for modulating said digital signal to a second analog signal different from said first analog signal; a first filter for attenuating, in a first frequency band, the amplitude of said second analog signal; a second filter for attenuating, in a second frequency band, the amplitude of said first analog signal, said first and second bands being nonoverlapping; means for combining said first and second filtered analog signals to form a single composite analog signal, a third filter for attenuating, in said second frequency band, the amplitude of said composite signal to extract said first analog signal; a fourth filter for attenuating, in said first frequency band, the amplitude of said composite signal to extract said second analog signal; and means for demodulating said second analog signal to said digital signal; and wherein said modulator and said demodulator utilize frequency shift keying technology.

Claim 9

A system for combining an unmodulated first analog signal and a digital signal, said system comprising: means for modulating said digital signal to a second analog signal different from said first analog signal; a first filter for attenuating, in a first frequency band, the amplitude of said second analog signal; a second filter for attenuating, in a second frequency band, the amplitude of said first analog signal, said first and second bands being nonoverlapping; means for combining said first and second filtered analog signals to form a single composite analog signal, a third filter for attenuating, in said second frequency band, the amplitude of said composite signal to extract said first analog signal; a fourth filter for attenuating, in said first frequency band, the amplitude of said composite signal to extract said second analog signal; and means for demodulating said second analog signal to said digital signal; and wherein said modulator and said demodulator utilize frequency shift keying technology.

Claim 10

A method for combining an unmodulated first analog signal and a digital signal, said process comprising: modulating said digital signal to a second analog signal different from said first analog signal; attenuating, in a first frequency band, the amplitude of said second analog signal; attenuating, in a second frequency band, the amplitude of said first analog signal, said first and second bands being nonoverlapping; combining said first and second analog signals to form a single composite analog signal; attenuating, in said second frequency band, the amplitude of said composite signal to extract said first analog signal; attenuating, in said first frequency band, the amplitude of said composite signal to extract said second analog signal; demodulating said second analog signal to said digital signal; and wherein: said first band consists of frequencies below a -3 dB cutoff frequency, said second band consists of frequencies above said cutoff frequency, said first signal consists essentially of frequencies contained within said first band, and said second signal consists essentially of frequencies contained within said second band.

Claim 11

A method for combining an unmodulated first analog signal and a digital signal, said process comprising: modulating said digital signal to a second analog signal different from said first analog signal; attenuating, in a first frequency band, the amplitude of said second analog signal; attenuating, in a second frequency band, the amplitude of said first analog signal, said first and second bands being nonoverlapping; combining said first and second analog signals to form a single composite analog signal; attenuating, in said second frequency band, the amplitude of said composite signal to extract said first analog signal; attenuating, in said first frequency band, the amplitude of said composite signal to extract said second analog signal; demodulating said second analog signal to said digital signal; and wherein: said first band consists of frequencies below a -3 dB cutoff frequency, said second band consists of frequencies above said cutoff frequency, said first signal consists essentially of frequencies contained within said first band, and said second signal consists essentially of frequencies contained within said second band.

Claim 13

A method for combining an unmodulated first analog signal and a digital signal, said process comprising: modulating said digital signal to a second analog signal different from said first analog signal; attenuating, in a first frequency band, the amplitude of said second analog signal; attenuating, in a second frequency band, the amplitude of said first analog signals, said first and second bands being nonoverlapping; combining said first and second analog signals to form a single composite analog signal; attenuating, in said second frequency bands, the amplitude of said composite signal to extract said first analog signal; attenuating, in said first frequency bands, the amplitude of said composite signal to extract said second analog signal; demodulating said second analog signal to said digital signal; and wherein the steps of modulating said digital signal, and of demodulating said second analog signal are performed utilizing phase shift keying technology.

Claim 14

A method for combining an unmodulated first analog signal and a digital signal, said process comprising: modulating said digital signal to a second analog signal different from said first analog signal; attenuating, in a first frequency band, the amplitude of said second analog signal; attenuating, in a second frequency band, the amplitude of said first analog signals, said first and second bands being nonoverlapping; combining said first and second analog signals to form a single composite analog signal; attenuating, in said second frequency bands, the amplitude of said composite signal to extract said first analog signal; attenuating, in said first frequency bands, the amplitude of said composite signal to extract said second analog signal; demodulating said second analog signal to said digital signal; and wherein the steps of modulating said digital signal, and of demodulating said second analog signal are performed utilizing phase shift keying technology.

Claim 15

A method for combining an unmodulated first analog signal and a digital signal, said process comprising: modulating said digital signal to a second analog signal different from said first analog signal; attenuating, in a first frequency band, the amplitude of said second analog signal; attenuating, in a second frequency band, the amplitude of said first analog signal, said first and second bands being nonoverlapping; combining said first and second analog signals to form a single composite analog signal; attenuating, in said second frequency band, the amplitude of said composite signal to extract said first analog signal; attenuating, in said first frequency band, the amplitude of said composite signal to extract said second analog signal; demodulating said second analog signal to said digital signal; and wherein the steps of modulating said digital signal, and of demodulating said second analog signal are performed utilizing quadrature phase shift keying technology.

Claim 16

A method for combining an unmodulated first analog signal and a digital signal, said process comprising: modulating said digital signal to a second analog signal different from said first analog signal; attenuating, in a first frequency band, the amplitude of said second analog signal; attenuating, in a second frequency band, the amplitude of said first analog signal, said first and second bands being nonoverlapping; combining said first and second analog signals to form a single composite analog signal; attenuating, in said second frequency band, the amplitude of said composite signal to extract said first analog signal; attenuating, in said first frequency band, the amplitude of said composite signal to extract said second analog signal; demodulating said second analog signal to said digital signal; and wherein the steps of modulating said digital signal, and of demodulating said second analog signal are performed utilizing quadrature phase shift keying technology.

Claim 17

A method for combining an unmodulated first analog signal and a digital signal, said process comprising: modulating said digital signal to a second analog signal different from said first analog signal; attenuating, in a first frequency band, the amplitude of said second analog signal: attenuating, in a second frequency band, the amplitude of said first analog signal, said first and second bands being nonoverlapping: combining said first and second analog signals to form a single composite analog signal; attenuating, in said second frequency band, the amplitude of said composite signal to extract said first analog signal; attenuating, in said first frequency band, the amplitude of said composite signal to extract said second analog signal; demodulating said second analog signal to said digital signal; and wherein the steps of modulating said digital signal, and of demodulating said second analog signal are performed utilizing frequency shift keying technology.

Claim 18

A method for combining an unmodulated first analog signal and a digital signal, said process comprising: modulating said digital signal to a second analog signal different from said first analog signal; attenuating, in a first frequency band, the amplitude of said second analog signal: attenuating, in a second frequency band, the amplitude of said first analog signal, said first and second bands being nonoverlapping: combining said first and second analog signals to form a single composite analog signal; attenuating, in said second frequency band, the amplitude of said composite signal to extract said first analog signal; attenuating, in said first frequency band, the amplitude of said composite signal to extract said second analog signal; demodulating said second analog signal to said digital signal; and wherein the steps of modulating said digital signal, and of demodulating said second analog signal are performed utilizing frequency shift keying technology.