Abstract: The equipment for determining the position of a metal pin in a bone comprises a support, a radiating self-induction coil mounted on the support and two receiving self-induction coils mounted on the support. A receiving coil is arranged on either side of the radiating coil but the space between the receiving coils facing the radiating coil remains free. The radiating coil is supplied by an oscillator with a frequency of about 30 kHz. The receiving coils control signaling members according to the phase-shift of signals generated by the receiving coils.

Abstract: A simple yarn unwinding apparatus which enables smooth and regular yarn unwinding of bobbins and thereby reduces yarn breakage. The apparatus comprises a bobbin of yarn mounted on a frame, a yarn take-up device for pulling the yarn from said bobbin. A light yarn guide is rotatably mounted on the frame coaxial with the bobbin and substantially frictionless upon rotation. The yarn guide is provided with a yarn passage along its axis of rotation and terminating short of the side of the bobbin opening on the yarn to gradually radially displace the yarn from the bobbin and to convey it to said yarn take-up device, while converting the motion from rotational into translational and dampening of abrupt motions of the yarn leaving the bobbin.

Abstract: Laser unit for directing a laser beam in a strictly vertical direction, comprising a laser proper having a substantially vertical axis, an afocal system, an optical device for automatically correcting the verticality of the laser beam, and a base structure provided with means for supporting the assembly of said laser, afocal system and optical device in such position that the laser axis be substantially vertical. This invention is applicable to all fields and techniques in which it is desired to determine with the maximum precision the vertical at a given locus where the laser is installed.

Abstract: Apparatus for measuring the frontal power of corneal contact lenses made of a somewhat hydrophilic material and having a predetermined index of refraction in a liquid having itself a predetermined index of refraction. This apparatus comprises a sighting optical system and a measuring optical system spaced from each other and having a common optical axis extending substantially vertically at least in the gap between said two optical systems. It further comprises a small cup disposed in said gap and filled with said liquid, the cup bottom comprising a fluid-tight window centered to said optical axis and means for supporting a contact lens in said liquid in a position centered to said optical axis.

Abstract: This adjustable base, notably for topometric and similar apparatus, comprises a case, a movable member in said case having a substantially vertical axis and bearing on the bottom of said case through three balls, a pair of screws perpendicular to each other for adjusting the verticality of the axis of said movable member, at least one return spring, a pair of passages formed partly in the bottom of said case and partly in the opposite lower face of the movable member, the first passage being defined by a flat surface and by a V-sectioned groove converging toward each other in the direction of a first one of the three balls, the second passage being defined by two other V-sectioned grooves converging toward each other in the direction of said first ball, the two other balls being disposed each in a respective one of the two passages, and each adjustment screw engaging the ball disposed in the relevant passage for pivoting the movable member about the first ball.