Patent ID: 7671372

Claim:
A digital signal transfer device comprising: a generating section that generates a square-wave carrier signal; a modulating section that generates a modulated signal by varying said carrier signal in accordance with a digital input signal; wherein said modulating section comprises: a first circuit comprising one of an AND gate circuit or an OR gate circuit, wherein a first input of the first circuit is said digital input signal, and wherein a second input of the first circuit is said carrier signal; an inverter circuit configured to output an inverted signal of said carrier signal; and a second circuit comprising one of an AND gate circuit or an OR gate circuit, wherein a first input of the second circuit is said digital input signal, and wherein a second input of the second circuit is an inverted signal of said carrier signal, a demodulating section that generates an output signal in which a waveform of said digital input signal is restored from said modulated signal wherein the demodulating section belongs to a power source system different from said modulating section, wherein the demodulation section comprises a switch section configured to turn on or off in accordance with the modulated signal, and wherein the demodulating section is configured to restore a waveform of the digital input signal in response to operation of the switch section; and an isolating transfer section that connects said modulating section and said demodulating section in an electrically isolated condition and that transfers said modulated signal from said modulating section to said demodulating section, wherein the isolating transfer section comprises a pulse transformer.