Abstract: A local area computer network provides distributed parallel processing. The network comprises a plurality of workstations or personal computers, each having preemptive multitasking for the interactive execution of a local task in the foreground concurrently with a remote network subtask in the background. A large compute-intensive task may be partitioned into a plurality of parallel subtasks executed simultaneously with each subtask executed in the background by a respective workstations without substantial interference with the local task being executed concurrently in the foreground. The computer time and processing power which would otherwise be wasted while waiting for slow input/output operations is instead utilized to provide a powerful parallel multiprocessor system for handling compute-intensive tasks too large for an individual workstations.

Abstract: A novel drive stage provides with low distortion a large amplitude signal, such as required for driving a cathode-follower output stage of a power amplifier. The drive stage comprises an amplification substage and a load substage. Each substage comprises two series connected vacuum tubes. Each substage is provided with a respective voltage divider network to provide that the two tubes of each substage share approximately equally both the quiescent static voltage and the dynamic voltage of the substage. The load substage coacts with the amplification substage to provide a novel mu-follower or SRPP circuit having approximately twice the voltage swing of a conventional circuit. This approximately quadruples the maximum power output of the cathode-follower amplifier.

Abstract: A cathode-follower power output stage is driven by a novel drive stage to provide with low distortion the large signal required to drive the output stage. The drive stage comprises two series connected vacuum tubes which share the large static and dynamic voltages of the drive stage so as to provide a drive signal having a large voltage swing, without generating audible distortion and without subjecting the drive stage tubes to excessively high voltages. The plate of a first drive tube is connected to the cathode of the second drive tube. A load impedance is connected from a B+ power supply terminal to the plate of the second drive tube. The grid of the second drive tube is driven by a signal responsive voltage divider network driven by the plate of the second drive tube.

Abstract: A motional feedback loudspeaker system provides acceptable bass performance even with inexpensive speakers by the reduction of nonlinear distortion with the use of feedback derived from the back emf signal generated by the motion of the voice-coil within the magnet field. A novel linearizing circuit corrects the nonlinearity of the back emf signal due to the falloff of the BL factor as a function of cone displacement. The linearizing circuit is a recursive feedback loop comprising a multiplier for multiplying the back emf signal by a corrective function which is the inverse of the BL nonlinearity so as to provide a velocity signal linearly proportional to the cone velocity, an integrator for integrating the velocity signal to generate a displacement signal linearly proportional to the cone displacement, and a correction generator comprising a nonlinear curve shaper responsive to the displacement signal to generate said corrective function.

Abstract: A motional feedback loudspeaker system wherein the loudspeaker distortion is reduced by a negative feedback signal derived from the back electromotive force induced by the motion of the voice-coil within the magnet field. It is essential that the feedback signal be a linear function of the loudspeaker cone motion, and this is achieved by locating the voice-coil within a uniform elongated cylindrical magnetic field of substantially constant flux density and having an axial length substantially greater than the axial length of the voice-coil. Therefore the voice-coil is underhung so as to remain immersed within the uniform field even at peak displacements of the voice-coil during maximum excursions of the speaker cone. The uniform elongated magnetic field is preferably provided by a cylindrical radially polarized magnet of neodymium.