Multiple point switching apparatus

Claim 2

In combination in switching apparatus, first and second spaced and insulated conductors, a grounded conductor disposed intermediate said first and second conductors, a key including a key conductor having a first portion movable into proximity with said first conductor and a second portion movable into proximity with said second conductor, means for biasing said key to a quiescent condition, means for moving said key conductor, means inhibiting physical contact between said key conductor with either of said first and second conductors, an oscillator connected to said first conductor for supplying output oscillations thereto, and oscillation-responsive switch means connected to said second conductor.

Claim 3

A combination as in claim 1 wherein said key conductor includes an indented shaped portion for maintaining a relatively large spacing from said grounded conductor.

Claim 4

A combination as in claim 1 wherein said oscillation-responsive switch means comprises a transistor connected in a grounded emitter configuration, a capacitor connected in parallel with the collector emitter of said transistor, and means connecting the base of said transistor with said second conductor.

Claim 5

A combination as in claim 3, further comprising an additional plurality of biased keys and oscillation-responsive switch means, said second conductor including a plurality of insulated segments each associated with a different one of said keys and switch means, a diode encoding matrix including input and output conductors, said switch means being coupled to said matrix input conductors, and a plurality of sense amplifiers each connected to a different one of said matrix output connectors, each of said sense amplifiers including threshold means for constraining said amplifier to reside in first and second characteristic states when the input voltage applied thereto is disposed above and below said input voltage threshold.

Claim 6

A combination as in claim 4, further comprising a strobe circuit, OR logic means connecting the input of each of said sense amplifiers with the input of said strobe circuit, said strobe circuit having a threshold such that said strobe circuit resides in a first and second output state when the input voltage applied thereto is disposed above and below said threshold level, said threshold for said strobe circuit requiring a greater signal change for switching than said threshold of said sense amplifiers, said strobe circuit including output means for selectively enabling said sense amplifiers.

Claim 7

A combination as in claim 5 further comprising means for sensing the cumulative current flow through said switch means, and means responsive to said current sensing means supplying an indication that more than one of said switch means is conducting at any time for disabling said sense amplifiers.

Claim 8

A combination as in claim 6 wherein said sense amplifier disabling means comprises a difference amplifier for selectively disabling said strobe circuit.

Claim 9

A combination as in claim 1 further comprising an additional plurality of said keys and said switch means, said second conductor including a plurality of insulated segments each associated with a different key and switch means, output line means selectively having signals representative of the conduction states of said switch means impressed thereon, and means for disabling said switch means when more than one of said keys are coincidentally depressed.

Claim 10

In combination in switching apparatus, an oscillator, plural switch means, a plurality of key means selectively operable to effect a relatively high capacitance coupling path from said oscillator to an associated one of said switch means, each of said switch means including a transistor in a grounded emitter configuration and a capacitor connected in parallel with the collector-emitter of said transistor, a diode encoding matrix having input and output conductors, means coupling said switch means to said matrix input conductors, plural sense amplifier means each exhibiting an input switching threshold and having their inputs connnected to a different one of said matrix output conductors, an OR logic gate having an output and plural inputs each connected to a different one of said matrix output conductors, strobe circuit means having an input connected to the output of said OR gate and an output for selectively enabling said sense amplifier means, said sense amplifier means being controlled by said strobe circuit means, said strobe circuit having a threshold which requires a greater signal change for enabling said sense amplifier means than the switching thresholds for said sense amplifier means.

Claim 11

In combination in switching apparatus, an oscillator, plural switch means, a plurality of key means selectively operable to effect a relatively high capacitance coupling path from said oscillator to an associated one of said switch means, each of said switch means including a transistor in a grounded emitter configuration and a capacitor connected in parallel with the collector-emitter of said transistor, a diode encoding matrix having input and output conductors, means coupling said switch means to said matrix input conductors, plural sense amplifier means each exhibiting an input switching threshold and having their inputs connnected to a different one of said matrix output conductors, an OR logic gate having an output and plural inputs each connected to a different one of said matrix output conductors, strobe circuit means having an input connected to the output of said OR gate and an output for selectively enabling said sense amplifier means, said sense amplifier means being controlled by said strobe circuit means, said strobe circuit having a threshold which requires a greater signal change for enabling said sense amplifier means than the switching thresholds for said sense amplifier means.

Claim 12

A combination as in claim 9 further comprising means for disabling said sense amplifier means when more than one of said switch means is conducting.

Claim 13

A combination as in claim 10 wherein said sense amplifier disabling means includes means for sensing the current flow through such switch means, and a difference amplifier connected to said current sensing means for selectively disabling said strobe circuit.