A dual axis position indicator for producing variable maximum, variable resistances for supplying variable signals to a computer indicating the respective degrees of displacement of a controlled element along each of two axes comprising:
- a first variable resistor having a variable resistance and first and second terminals;
- a first fixed resistance resistor and a first transistor having first, second, and control terminals, the first fixed resistor being connected to the first and second terminals of the first transistor, the first transistor being connected in series with the first variable resistor at the second terminal of the first variable resistor and the first terminal of the first transistor as a first series circuit;
- a second fixed resistance resistor, a first potentiometer having a fixed resistance and a variable position contact movable along and electrically connected to the fixed resistance of the first potentiometer, and a third fixed resistance resistor, the second fixed resistor, the first potentiometer, and the third fixed resistor being connected in series as a second series circuit, the first and second series circuits being electrically connected together (i) at the first terminal of the first variable resistor and at the second fixed resistor and (ii) at the second terminal of the first transistor and the third fixed resistor, i.e., in parallel, the connection of the third fixed resistor and the second terminal of the first transistor being a first output terminal of the indicator;
- a first amplifier having a first inverting input terminal and second non-inverting input terminal and an output terminal, the first inverting input terminal and second non-inverting input terminal of the first amplifier being connected to the second terminal of the first variable resistor and the variable position contact of the first potentiometer, respectively, the output terminal of the first amplifier being connected to the control terminal of the first transistor whereby the maximum resistance at the first output terminal of the indicator is controlled by the variable position contact of the first potentiometer;
- a second variable resistor having a variable resistance and first and second terminals;
- a variable displacement displaceable element coupled to the first and second variable resistors for varying the resistances of the first and second variable resistors in response to the degree of displacement of the displaceable element along first and second axes, respectively;
- a fourth fixed resistance resistor and a second transistor having first, second, and control terminals, the fourth fixed resistor being connected to the first and second terminals of the second transistor, the second transistor being connected in series with the second variable resistor at the second terminal of the second variable resistor and the first terminal of the second transistor as a third series circuit;
- a fifth fixed resistance resistor, a second potentiometer having a fixed resistance and a variable position contact movable along and electrically connected to the fixed resistance of the second potentiometer, and a sixth fixed resistance resistor, the fifth fixed resistor, the second potentiometer, and sixth fixed resistor being connected in series as a fourth series circuit, the third and fourth series circuits being electrically connected together (i) at the first terminal of the second variable resistor and at the fifth fixed resistor and (ii) at the second terminal of the second transistor and the sixth fixed resistor, i.e., in parallel, the connection of the sixth fixed resistor and the second terminal of the second transistor being a second output terminal of the indicator;
- and
- a second amplifier having a first inverting input terminal and a second non-inverting input terminal and an output terminal, the first inverting input terminal and the second non-inverting input terminal of the second amplifier being connected to the second terminal of the second variable resistor and the variable position contact of the second potentiometer, respectively, the output terminal of the second amplifier being connected to the control terminal of the second transistor whereby the maximum resistance at the second output terminal of the indicator is controlled by the variable position contact of the second potentiometer.