Applied Spectrum Technologies, Inc.

Wadia Digital Corporation

Jeffrey L Ward

Charles H Hustig

Donald W Moses

Robert S Bradford

Robert W Moses

James M Kresse

Wayne P Olson

Raymond S Miller

A direct power output digital to analog conversion of digital audio signals operates to directly convert digital audio signals into an analog power audio output signal capable of driving a speaker, such that there is no need for further amplification or modification of the audio output signal after the direct power output digital to analog conversion of the digital audio signals. The direct power output digital to analog conversion incorporates a digital-to-analog converter within the same feedback circuit as a current-to-voltage power amplifier by using a single resistive feedback network to supply the feedback signal from the output terminal of the current-to-voltage power amplifier to the summing junction of the same current-to-voltage power amplifier.

Direct power output digital to analog conversion of digital audio signals

A method and system is provided for a digital audio system to reconstruct a digital audio signal using time domain interpolation and direct power digital-to-analog conversion. A signal processor performs the time domain interpolation on an original digital audio signal to allow for the proper recreation of the original audio signal and a direct power output digital-to-analog converter generates an analog power audio output signal from the interpolated digital audio signal that can directly drive a speaker to produce the sound waves represented by the audio output signal. The signal processor and direct power output digital-to-analog converter allow a digital audio system to more precisely reconstruct an analog power output audio signal from a digital audio signal such that there is no need for further amplification of the audio output signal and such that there will be no perceptible difference between the reconstructed digital signal and the original analog signal.

Method and system for time domain interpolation of digital audio signals

A communications system which enables enhanced services to be provided over cable TV systems. The design of the system is such that amplification is not required. Therefore, two-way transmission is possible on the low band of 'two-way capable' cable systems and intermediate power failures do not affect transmission. Transmission of data takes place in the low band frequency range of five to thirty megahertz. The system design is such that it can withstand over a hundred dB loss between the remote terminal and the head-end. Carrier frequencies, when received, are interleaved for purposes of decoding and microprocessor based controls are used for automatic gain control and error correction. In a preferred embodiment of the invention, two thousand five hundred carriers, each transmitting eight digital data channels of information can be simultaneously transmitted from remote terminals without any effect whatsoever on the TV signals being transmitted at the high band frequencies. The resulting system is a very economical and dependable method to achieve passive transmission of data over cable TV systems.

Passive transmission of data over cable TV systems

A high speed and relatively error free communications system is disclosed which enables the high speed transmission of data at a 19.2 kilobit per second rate. The data is transmitted over the same communications medium as voice transmissions, the data transmission being virtually imperceptible to the user of the analog telephone system. Connection to and from the data terminals is made through an RS232C interface. A spread spectrum technique is utilized which 'whitens' the signals of the data terminal regardless of whether the terminal is idle, transmitting or receiving data. Virtual error free transmission is achieved by interleaving bits, so that noise does not destroy the data, and by error detection and correction techniques which assure that the data, as received, is identical to that transmitted. By using a variable pseudo random code, privacy of data communications are enhanced and cross-talk is substantially eliminated. The resulting system is one that can use a single twisted pair wire for transmission and is capable of transmitting data at a high rate of speed while leaving the analog voice transmission resident and unaffected on the line.

Growing community of inventors

Hudson, WI, United States of America

Jeffrey L Ward