Abstract: A piezo-controlled dynamic probe or feeler head for measuring installations and measuring machine, which is in an operative connection with a measurement evaluating or plotting unit and, selectively with a measuring machine control. The probe is constructed from two mutually independently operating measuring signal generating installations, which are equipped with mutually separate or independent circuits and which act in such a manner on the measuring evaluating or plotting unit and, selectively, on the measuring machine control, that upon the generation of a signal from the first measuring signal generating installation, stored data regarding the position of the probe can be recognized as being valid only at the presence of a confirmation or acknowledging signal from the second measuring signal generating installation.

Abstract: This invention relates to apparatus for contact-free disintegration of kidney stones or other calculi of the kind in which electrical discharges are generated across an under water spark gap in the focus line of an elliptical reflector having annular or spiral surfaces. The calculus which is to be disintegrated is located into the focus of the reflector and in accordance with invention electrode elements are positioned at intervals in the focus line of this reflector on an insulating carrier. The latter is provided with high tension connectors at its ends and the electrode elements are arranged to form consecutive individual spark gaps.The gaps between the electrode elements may be of constant dimensions or may vary so as to produce variations in pressure distributed at a focus point if so desired.

Abstract: Ultrasonic waves, produced from electric signals at one end of a measuring section having the length s, are transmitted through the measuring section and re-transformed into electric signals at the opposite end of the measuring section. The transit time T.sub.1 of the ultrasound in the flow direction of the media, and the transit time T.sub.2 of the ultrasound in the opposite direction, are determined, digitized, inverted into their respective reciprocal values 1/T.sub.1 and 1/T.sub.2 to establish the difference 1/T.sub.1 - 1/T.sub.2 whereby the flow velocity v = s/2 (1/T.sub.1 - 1/T.sub.2) may be determined. The device includes a rectilinear conduit section through which the media flows and preferably made of a glass ceramic material having a zero temperature coefficient. Ultrasonic transducers are located at the opposite ends of the measuring section and have concave surfaces which face each other and are located in mutual confocal relation.