Abstract: In an electrical system of the type in which a digitally-encoded signal is determined at least in part by the difference between a present value of an analog input signal and a reconstructed signal representative of a past value of the input signal and including signal generating means for generating said reconstructed signal, which means is responsive to a reference signal, improved circuitry for generating the reference signal. The improved circuitry comprises a ladder network which increases the magnitude of the reference signal as a function of the length of time the digitally-encoded signal continuously remains in either digital state without a change to the other digital state.

Abstract: In an electrical system for generating a digitally-encoded signal from an analog signal and a reference signal, a circuit for reducing quantization noise comprises a bandpass filter which passes audible frequency components, the output of which filter is used to adjust the encode signal so as to reduce the level of audible components in a signal decoded from the encoded one.

Abstract: In an electrical system of the type in which a digitally encoded signal is determined at least in part by the difference between a present value of an input signal and a reference signal representative of a past value of the input signal, improved circuitry for generating the reference signal. The improved circuitry comprises extraction means including a filter for extracting from the pattern of bits in the digitally encoded signal information relating to the time derivative of the present value of the input signal and an envelope detector for processing the output of the filter to provide a control signal, and integrating means responsive to the control signal to provide the reference signal.

Abstract: In an electrical system of the type in which a digitally-encoded signal is determined at least in part by the difference between a present value of an input signal and a reconstructed signal representative of a past value of the input signal and including a filter for extracting from the digital signal information relating to the time derivative of the input signal, peak detection means for determining the peak value of the output of said filter, and a signal generating means responsive to a reference signal determined from the output of said peak detection means for generating the reconstructed signal, improved circuitry for generating the reference signal. The circuit comprises weighting means for increasing the magnitude of the input to the filter as a function of the preponderance of one or the other state in said digitally-encoded signal.

Abstract: In an electrical system of the type in which a digitally encoded signal is determined at least in part by the difference between a present value of an input signal and a reference signal representative of a past value of the input signal, improved circuitry for generating the reference signal. The improved circuitry comprises extraction means including a filter for extracting from the pattern of bits in the digitally encoded signal information relating to the time derivative of the present value of the input signal to provide a corresponding control signal, and integrating means responsive to the control signal to provide the reference signal.

Abstract: In an electrical system of the type in which a digitally-encoded signal is determined at least in part by the difference between a present value of an input signal and a reconstructed signal representative of a past value of the input signal and including a filter for extracting from the digital signal information relating to the time derivative of the input signal, peak detection means for determining the peak value of the output of said filter, and a signal generating means responsive to a reference signal determined from the output of said peak detection means for generating the reconstructed signal, improved circuitry for generating the reference signal. The circuit comprises weighting means for increasing the magnitude of the input to the filter as a function of the preponderance of one or the other state in said digitally-encoded signal.