Abstract: Selected touch point locating apparatus has an array of two or more electrical touch members constituted by impedance elements coupled to a circuit for causing electric current to flow through a selected touch point as the algebraic sum of separate currents through the electrical touch members. The relative amplitudes are translated into at least two signals corresponding to the location in two axes of the selected touch point.

Abstract: A system is described for coupling two voltage sources to a resistive plane, surface or layer so as to produce a uniform electric field in said plane with orthogonal components along the two axes of the plane generated by the two voltage sources so that coordinates of position of a digit or finger in the field may be determined. Techniques are described for fabricating both the plane and the coupling elements from the same resistive material. It is also shown how nonlinear electric fields can be created while preserving orthogonality. Three-dimensional fields of predetermined characteristics can be created by extending the techniques to curved surfaces and by using multiple surfaces.

Abstract: A human-machine interface apparatus includes a first, or phase, surface with associated circuitry so devised that an alternating electrical field is created above the surface with its phase, relative to a fixed point on the surface, changing continuously along an axis of the surface; a second, or pickup, surface located so that when the operator of the interface apparatus inserts a finger in the field an electrical signal with phase corresponding to the point of insertion is transmitted through the operator's body to the pickup surface; and a phase discriminator with one input connected to the pickup surface and a reference input connected to an alternating voltage source of predetermined phase relationship to the alternating electrical field at a fixed point on the phase surface. The preferred embodiment combines two such apparatuses, sharing common phase and pickup surfaces but operating at different frequencies, to provide outputs corresponding to two orthogonal axes on the phase surface.

Abstract: A human-machine interface apparatus includes a first, or phase, surface with associated circuitry so devised that an alternating electrical field is created above the surface with its phase, relative to a fixed point on the surface, changing continuously along an axis of the surface; a second, or pickup, surface located so that when the operator of the interface apparatus touches the phase surface an electrical signal with phase corresponding to the spot touched is transmitted through the operator's body to the pickup surface; and a phase discriminator with one input connected to the pickup surface and a reference input connected to an alternating voltage source of predetermined phase relationship to the alternating electrical field at a fixed point on the phase surface. The preferred embodiment combines two such apparatuses, sharing common phase and pickup surfaces but operating at different frequencies, to provide outputs corresponding to two orthogonal axes on the phase surface.