Abstract: Apparatus and a concommitant method for generating an approximation of a logarithmically attenuated value of a digital signal in predefined increments. Specifically, the apparatus comprises a shift register, a latch and an adder. The shift register selectively shifts the digital signal a first number of bits to the right to produce a first shifted signal and then a second number of bits to the right to produce a second shifted signal. The latch is connected to the shift register and latches the first shifted digital signal while the digital signal is being shifted to form the second shifted signal. The adder is connected to the shift register and the latch and adds the first shifted signal to the second shifted signal to produce the attenuated value of the input digital signal.

Abstract: A method and apparatus is disclosed for detecting and concealing errors in stored digital samples. A multibit digital input sample is received and an error detecting code, corresponding to that input sample is calculated. Then a multibit digital storage sample is generated by substituting the error detecting code for the same number of least significant bits of the input sample. The storage sample is then stored in a memory device. A previously stored sample is retrieved from the memory device and is analyzed to detect whether an error has occurred. If an error is detected, a substitute sample is produced for the retrieved sample, otherwise the retrieved sample is produced.

Abstract: A method and apparatus is disclosed for detecting and concealing errors in stored digital samples. A multibit digital input sample is received and an error detecting code, corresponding to that input sample is calculated. Then a multibit digital storage sample is generated by substituting the error detecting code for the same number of least significant bits of the input sample. The storage sample is then stored in a memory device. A previously stored sample is retrieved from the memory device and is analyzed to detect whether an error has occurred. If an error is analyzed to detected, a substitute sample produced for the retrieved sample, otherwise the retrieved sample is produced.

Abstract: Portable electronic equipment is disclosed which includes a source of power and operational circuitry. A load device, which may be internal or external to the equipment, is coupleable to the operational circuitry. A switch is coupled between the power source and the operational circuitry and connects the power source to the operating circuitry only when the load device is coupled to the operational circuitry. In portable audio equipment, for example, the switch connects the power source to the operational circuitry only if an external or the internal speaker is coupled to the operational circuitry.

Abstract: An interpolation filter includes a subtractor, a weighting circuit and an adder, wherein the subtractor is conditioned to form differences of adjacent original samples, and the weighting circuit weights the differences with a predetermined value. The adder is arranged to a) pass an original sample; b) add a weighted difference to the original sample; and c) successively add the weighted difference to the previously generated sample to form successive samples.