Abstract: A digitizing tablet interactive with a stylus which is inductively coupled to a grid is disclosed. The grid includes a first plurality of narrow uniformly sized and spaced U shaped loops of conductive material disposed to define a first coordinate axis of the grid and a second plurality of narrow uniformly sized and spaced U shaped loops of conductive material disposed to define a second coordinate axis of the grid. One end point of each loop in each plurality of loops is connected to a common conductor which serves as one output terminal for that plurality of loops. The other end point of each loop in the same plurality of loops is connected to a multiplexor whose output is connected to a conductor which serves as the other output terminal for that plurality of loops. Voltage signals induced in the loops when the stylus is positioned above the grid and a coil in the stylus is energized are processed to generate data signals corresponding to the position of the stylus relative to the grid structure.

Abstract: A digitizing tablet system of the type including a tablet, a stylus and associated electronics which is constructed to correct for tilt errors when the stylus axis is tilted relative to the tablet is disclosed. The tablet includes a housing having a rectangular coordinate grid of electrical conductors. The stylus includes an elongated tubular member having a tip at one end, a first coil which is located at a first axial distance from the tip and a second coil which is located at a second axial distance from the tip, the second distance being different from the first distance. A voltage signal is applied to each coil sequentially. The signal applied to each coil induces a voltage in each conductor in the grid.

Abstract: Apparatus for filtering a sequence of digital values representing a stroke of a stylus on a tablet averages sets of digital values, resamples the averaged digital values to accept only those having greater than a minimum amplitude separation and then averages sets of the resampled digital values.

Abstract: An electronic reverberation apparatus, for producing artificial reverberation on a purely electronic basis with a digital computer, comprises a plurality of loops having different delay times and adapted to form sound repetitions of diminishing intensity. Some of the loops have short delay times and have an all-pass characteristic. Others of the loops have long delay times. The loops are provided with tappings each of which has a particular delay time associated with it. The delay times of the tappings themselves and the sums, differences and quotients of these delay times are in a non-harmonic relationship to one another. Each tapping feeds a corresponding damping element whereby the output from each successive tapping is reduced such that the reduction in energy corresponds to an exponential function, and a delayed and repeated combination of unreverberated input signals is fed to an output from the loop circuit. For naturalness the output of each reverberation delay unit is randomly damped.