The Anaconda Company

Other

Ronald F McGuire

The present invention provides an apparatus and method for dual frequency demodulation of frequency shift keyed data signals and linear FM signals. A carrier frequency and first and second side bands are divided and multiplied by first and second local oscillators having different frequencies above and below the carrier frequency. The first oscillator frequency Fx1 is between the lower range F0 of the signal and the carrier frequency FC, and the second oscillator frequency Fx2 is provided between the upper range F1 of the signal and the carrier frequency FC, wherein F0&lt;Fx1&lt;FC&lt;Fx2&lt;F1. The multiplied divided signals are filtered and amplified and converted to either digital data prior to being read by a digital reader, such as a comparator or a conventional differential operational amplifier or linear signals by demodulating FM signals. The invention eliminates the need for intermediate frequency bandpass filters, and uses only low pass filters which can be incorporated into a monolithic integrated circuit as provided by the present invention.

Dual frequency demodulation apparatus for frequency shift keyed (FSK)

An out-of-band signaling method and apparatus are provided to facilitate the adaptation of payphones to telephone systems, as for example subscriber carrier systems. Part of the speech band is made unavailable to the subscribers and is employed for signaling DC line conditions from one end of the telephone system to the other.

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Anaheim, CA, United States of America

Ronald F McGuire