A graphic tablet includes a number of parallel electrodes whereto a series of patterns is presented in order to determine the position of a pen relative to the electrodes. As a result of such presentation, a series of code elements is formed on an electrode, which series can be picked up by the pen and is representative of the relevant electrode. When the patterns are suitably chosen, a short series of patterns suffices, so that the determination of the position requires less time.

A touch tablet is provided containing two sheets of insulating material each of which contains a plurality of spaced apart conductive lines. A resistive strip on each sheet contacts and connects electrically one end of each of the plurality of conductive lines on that sheet. Each resistive strip functions as a potentiometer. Mounted between the two sheets and spaced apart therefrom is a conductive middle sheet. The first and second sheets are mounted such that the first and second sets of a plurality of conductive lines on these sheets are orthogonal to each other. A user presses on one of the two sheets to bring all three sheets into contact. The impedence of each potentiometer is a function of the contact point. The potentiometer is used as part of an RC circuit to provide a variable time constant representative of the coordinate of the contact point.

The device according to the invention comprises a sensor formed by a plurality of capacitive or resistive electrodes. The user searches the symbol to be selected by displacing his finger on the sensor while looking at a control display unit. Any position of the finger on the sensor causes the display of to at least one symbol within an alphanumeric group, these symbols appearing sequentially on the control display. The device does not require any instruction for use nor any indicator marked on the instrument because its working principle is based on permanent visual feedback. The device is compatible with the dimensional requirements of portable instruments of small dimensions, e.g. timepieces.

A layer of carbon fiber materials sandwiched between two conductive layers provides a tactile feedback sensor which is particularly useful in manipulator systems for robotics and assembly automation.

A sensor having a particular application in the field of signature verification is disclosed. In the presently preferred embodiment, two plates are disposed in a spaced apart relationship and constructed to provide a plurality of electrical capacitors. Pressure applied at any point on one plate will cause deflection of that plate toward the other plate changing the capacitance of each capacitor. The change in capacitancegenerates electrical signals which may be combined and processed to provide signals indicative of the location on the plate at which the pressure was applied and indicative of the magnitude of its vertical component. In an alternate embodiment, first and second spaced apart parallel lines are disposed on one plate with a third ground line interlaced between the first and second lines. A voltage is applied across the first and second lines and the capacitance between the first and second lines is measured as a function of the distance between the plates. An additional alternate embodiment of the sensor utilizing a conductive fluid disposed between the plates is also disclosed.