Tactile numeric display device

Claim 1

A tactile numeric display apparatus comprising: a panel of insulating material; a plurality of sets of four electrical conductor pairs, the four electrical conductor pairs of each set being disposed in said panel of insulating material at the corners of quadrilaterals to simulate abbreviated Braille representation of Arabic numerals, each of the electrical conductor pairs including a central conductor having a diameter of from 3/64 to 1/8 inch, and a surrounding concentric annular conductor having a width of from 1/32 to 1/16 inch, with the separation of the conductors of the pair being from 3/64 to 1/8 inch, and the operative area of the central conductor being no greater than one-fourth of the operative area of the said annular conductor, each of the conductors of each electrical conductor pair having at least one end extending beyond one of the surfaces of said panel so that it can be touched by a user; a pulse generator means including a plurality of constant current sources, each of said constant sources having an input and an output connected to one of said pairs of electrical conductors, a plurality of bipolar waveform generators, each of said bipolar waveform generators having an input and an output connected to the input of one of said constant current sources, respectively, each of said bipolar waveform generators when activated generating from 20 to 250 pulse pairs per second, wherein each pair comprises a positive pulse of from 0.1 to 1 millisecond duration and a negative pulse of from 0.1 to 1 millisecond duration with a time interval between the positive and negative pulses of each pair being equal to the duration of one of said pulses and the peak to peak amplitude from the positive pulse to the negative pulse being such that the peak to peak current flowing from said constant current sources is between 0.5 and 10 milliampere; and means for selectively energizing said bipolar waveform generators in accordance with the Arabic numerals to be displayed.