Photoelectric keyboard for data input devices or the like

Claim 2

In a manually operated system for producing relatively short duration electric pulses in response to insertion of a plurality of partially light transmissive shutters in series within a light beam illuminating a photocell, the combination comprising: at least first and second threshold circuits connected to the output of said photocell, said first threshold circuit producing an output signal in response to the change of signal at the output of said photocell output resulting from insertion of a first of said shutters in said light beam, said second threshold circuit producing an output signal in response to the further reduction of said photocell output signal resulting from insertion of another of said shutters in said light beam while said first to be inserted shutter remains inserted; means responsive to said outputs of said threshold circuits to produce an electric pulse of relatively short duration corresponding to a signal output from any of said thresholD circuits.

Claim 3

A photoelectric keyboard system for data input and similar devices, having a first plurality of keys, a second plurality of photocells each arranged to be illuminated from a corresponding light source, and in which the light paths between said source and corresponding photocells are selectively, at least partially, interrupted in a predetermined pattern for generating a discrete electrical output code in response to operation of each key, comprising: first means including a predetermined plurality of partially light transmissive shutters connected to be inserted discretely into the light paths of the photocells corresponding to the code to be produced when each of said keys is operated; second means connected to the output of said photocells for contemporaneously generating a code pulse for each photocell providing an output signal change as a result of a first change of illumination produced by contemporaneous insertion of one of said shutters in the corresponding light path, said second means producing only one code pulse for each photocell output for each operation of said corresponding keys; and third means responsive to a second change of illumination resulting from key operation inserting a shutter in any of said light paths in which another shutter remains inserted from previous operation of another key, for producing a code pulse for any corresponding photocell output, said third means producing only one code pulse for each photocell output thus diminished by two of said shutters.

Claim 4

A photoelectric keyboard system for data input and similar devices, having a first plurality of keys, a second plurality of photocells each arranged to be illuminated from a corresponding light source, and in which the light paths between said source and corresponding photocells are selectively, at least partially, interrupted in a predetermined pattern for generating a discrete electrical output code in response to operation of each key, comprising: first means including a predetermined plurality of partially light transmissive shutters connected to be inserted discretely into the light paths of the photocells corresponding to the code to be produced when each of said keys is operated; second means connected to the output of said photocells for contemporaneously generating a code pulse for each photocell providing an output signal change as a result of a first change of illumination produced by contemporaneous insertion of one of said shutters in the corresponding light path, said second means producing only one code pulse for each photocell output for each operation of said corresponding keys; and third means responsive to a second change of illumination resulting from key operation inserting a shutter in any of said light paths in which another shutter remains inserted from previous operation of another key, for producing a code pulse for any corresponding photocell output, said third means producing only one code pulse for each photocell output thus diminished by two of said shutters.

Claim 5

Apparatus according to claim 2 in which said second means includes a first threshold switch connected one to each of said photocell outputs for producing an electrical step signal in response to insertion of one of said shutters in the corresponding light path and said third means includes a plurality of second threshold switch connected one to each of said photocell outputs for producing an electrical step signal in response to insertion of a second of said shutters while said first shutter remains in the corresponding light path, and differentiating means connected to the output of said threshold circuits to produce a relatively short pulse contemporaneously as each of said shutters is inserted into said light path.

Claim 6

Apparatus according to claim 3 in which said second means includes a differentiator and a flip-flop for each photocell, the outputs of said threshold circuits corresponding to each photocell being connected to said differentiator to produce a pulse at the time of each output signal change of said threshold circuits corresponding to insertion of each of said shutters in said corresponding light path for said photocell, and said flip-flop being connected to operate in response to said differentiator output to produce a standardized code pulse.

Claim 7

Apparatus according to claim 4 in which said flip-flop is a bistable circuit triggered by said differentiator output and in which one of said plurality of photocell, shutter, threshold circuit and differentiator combinations is arranged to operate in response to any of said key operations to produce a control pulse independent of said coding, and including delay means for delaying and applying said control pulse to said flip-flops as a reset pulse, thereby to determine the duration of said standardized code pulses.

Claim 8

Apparatus according to claim 5 in which each of said flip-flop outputs is applied to one input of an AND circuit, and the other inputs of all of said AND circuits are connected to receive said control pulse in undelayed form, the outputs of said AND circuits representing the coded output of said keyboard system.