The present invention relates to a device for inputting alphanumeric data into medical electromechanical apparatus. A German published patent application DE-OS 3404047, entitled "Video Game VDU Cursor Control Scale Change".
If such a device is for instance used for inputting numerical or alphanumerical data, respectively into medical electromechanical apparatuses then it is known to change the inputted data as a function of the deflection of an actuating element or as a function of the duration of the actuation of the element, respectively.
The displacement-actuation-relationship at the first alternative is an optimum from an anthropotechnical view since the user of the device senses automatically the amount of reaction, this means the amplitude of the inputted value as a result of his action expenditure.
Merely at large values of the input difference which, nevertheless, is to be inputted precisely the anthropotechnical optimum is lost due to the actuation expenditure. If, on the other hand, large displacements of actuating elements are related to large differences of the input amounts by an according design of the device then an exact input is not further possible.
With the second alternative a quasi-steady function between the action of the user and the reaction of the apparatus results and over large ranges of numbers the input expenditure is comparable to that of the steady input devices.
Finally, numerical input devices are known which have a non-steady behaviour as for instance code switches at which for each decimal number and therefore per decade a switching element is provided. Herewith a steady function between the user action and the amount of the newly inputted difference is not further given so that erroneous inputs may appear in a much larger extend than with steady justable input elements, this means a weak point from an anthropotechnical point of view. On the other hand, the actuation expenditure is nearly independent from the amount of the input difference without any loss of exactitude.
The above-mentioned known device relates to a cursor control with a joystick, the deflection of which is sensed by resistive elements in order to provide the amount and direction of the cursor displacement. In order to achieve this the tapped voltage signals after analog/digital-conversion are applied to a microprocessor for further processing.
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