Abstract: A signal frequency analyzer and frequency response shaping apparatus using digital techniques and apparatus and methods using the same which is applicable, in one embodiment thereof, to the enhancement of hearing in hearing impaired persons. Analog techniques are used in another embodiment of the invention. The invention includes hearing enhancement apparatus and methods which employ digital transformation, processing and memory functions for performing a wide range of hearing enhancement functions including the control of instantaneous signal gain levels as a function of instantaneous frequency and amplitude values of an audio signal. In another embodiment, the invention is applicable as a simple and inexpensive frequency analyzer which provides many of the characteristics of a complete Fast Fourier Transform (FFT) suitable for audio signals and other signals where a lower resolution FFT equivalent is acceptable.

Abstract: Several techniques are disclosed for producing modulation of a carrier signal wherein each transition of the modulated carrier signal includes a midrange level and/or two midrange characteristics, the level and/or ratio of the two midrange characteristics representing data carried by that transition. A simplified method over that disclosed in parent application Ser. No. 590,281, filed Mar. 16, 1984 now U.S. Pat. No. 4,613,974 is disclosed herein, and is referred to as a "flipped sine wave" method of producing the modulated carrier signal. Another technique, referred to as a "third harmonic modulation" technique uses the phase relationship between a fundamental and its third harmonic to produce the modulated carrier signal. A technique for storing the modulated carrier on magnetic media and correcting for offset resulting therefrom or from attenuation and advance of the third harmonic relative to the fundamental to permit accurate demodulation is disclosed.

Abstract: A composite video signal is input to a DC restore circuit and a sync separator circuit, the output of which is connected to a sync decoder circuit. The DC restore circuit includes a negative sensing peak sample and hold circuit that generates a first reference voltage equal to the sync tip voltage. A first differential amplifier substracts the composite video signal from the reference voltage and produces an inverted, level shifted replica, the sync tip voltage of which is zero. A second differential amplifier having an output clamping circuit, in conjunction with a comparator, produces a composite sync voltage that is used to strobe a sample and hold circuit to produce a second reference voltage. The replica is inverted by a second differential amplifier that subtracts the replica from the second reference voltage to produce the DC restored video signal, a "back porch" portion of which is accurately referenced to zero volts.

Abstract: A system and method for modulating a carrier signal wherein occurrence of the peaks in the modulated carrier signal conveys clocking information and each transition of a modulated carrier signal includes two midrange characteristics, the ratio of which represents data carried by that transition. Either analog or digital circuit techniques can be utilized to produce the modulated carrier signal, and either analog or digital techniques can be used to demodulate the modulated carrier signal in various embodiments of the invention. In an analog version of the modulator, a sinusoidal carrier signal is squared, alternate cycles of the squared waveform are phase shifted and clocked into analog multipliers, the gains of which are varied in response to an input data signal, the total gains being equal to a constant, and the multiplier outputs are summed to produce the modulated carrier signal. The ratios of the slopes of each transition represent the data.