Abstract: An apparatus for ultrasonically determining fluid flow passing through a measurement section includes a tube which has two ends and an average predetermined inner cross-sectional area; the tube constitutes the measurement section. A sound-emitting transducer is disposed near one end of the tube, which has a first sound-transfer surface, and a sound-receiving transducer disposed near the other end of the tube, which has a second sound transfer surface. Each sound transfer surface is disposed at a sufficiently large predetermined distance from a corresponding end of the tube, so as to permit the fluid flowing through the tube. A fluid-receiving chamber communicates with the one end of the tube, and has a first average cross-sectional area, and a fluid-discharge chamber communicates with the other end of the tube, and has a second average cross-sectional area.

Abstract: A transmitting device for generating communication signals to be superimposed on an AC distribution network. A resonant load circuit coupled to the network conductors includes a capacitor with a transistor switch and reverse polarity diode connected in parallel therewith. Current and voltage threshold circuits control the transistor switch such that an audio frequency communication signal is generated by the load circuit.

Abstract: A measuring transformer comprises a measuring conductor carrying the current I.sub.m to be measured, a pre-magnetizing winding which carries a pre-magnetizing current I.sub.v, and a magnetic field comparing means which is exposed to the magnetic field produced by the current I.sub.m and the magnetic field produced by the pre-magnetizing current I.sub.v and is alternately controlled in both directions of saturation. The magnetic field comparing means is a magnetic film which may be anisotropic, operated in the magnetic preferential direction, and have a thickness of at most a few microns. It may be secured to pole shoes of a magnetic core or arranged between a flat measuring conductor and a pre-magnetizing coil of flat cross-section. The measuring transformer can be used as an input transformer in a static electricity meter. In a further embodiment, the output pulses can be obtained directly from the magnetic field comparing means.

Abstract: This invention relates to communication systems of the type particularly useful in power line communications. Signals to be transmitted, which can be in the form of short, fixed frequency signals, are expanded in time and/or bandwidth to provide a longer signal with a variable frequency. At the receiver, power line noise, which is typically either short wideband noise or long narrowband noise, is removed and the remaining expanded signal is detected. The expanded signal can then be compressed in time and/or bandwidth to reproduce the original signal.

Abstract: A projection screen is disclosed having a surface formed by a plurality of irregularly distributed microstructural elements shaped like the outer surface of contiguous bubbles. Also disclosed is a method for making such projection screens.

Abstract: A detector for determining the presence of an electrical signal in the presence of noise, the electrical signal having at least two predetermined characteristics, includes a signal transforming device for obtaining a plurality of independent estimates of each characteristic, a classification device connected to the signal transforming device for sorting the plurality of independent estimates into at least two classes, and a counting device for signaling the presence of the electrical signal, when the number of the estimates within one class exceeds a predetermined number.

Abstract: An apparatus for measuring a.c. power which subtracts an average value of current and voltage from sampled instantaneous current and voltage values, respectively. The resultant current and voltage values are multiplied, so as to obtain a power measurement substantially free of any sampling errors and any d.c. levels.

Abstract: The invention relates to a combination of an apparatus for the transfer of fungible goods or services, for example, cashless payment for merchandise or services, with a transfer device having marked thereon a plurality of cancellable value units in the form of at least first and second types of optical markings different from one another, and arranged in a predetermined cyclical sequence on at least one track of the transfer device, without the occurrence of any gaps, but with a transition region formed between adjacent markings. The apparatus includes a reading device, inclusive of a light source, and at least first and second light sensors associated with the first and second types of optical markings, respectively. The reading device is arranged for reading and generating signals from the markings, and from the transition regions, and an activatable erasing device erases the markings in dependence of the number of value units to be cancelled.

Abstract: In a method and apparatus of identifying a document with the aid of at least two different types of optically readable markings disposed on the document, and of at least two light sensors, each individual marking modifying light impinging thereon in a characteristic manner, and wherein each light sensor is associated with a respective marking, and senses the light modified by the associated marking, the steps include placing the markings in a predetermined cyclical sequence on at least one track of the document, so as to avoid the creation of any optically readable gap, thereafter erasing at least selected portions of the markings, while maintaining in selected groups of two adjacent markings at least a portion of one of the markings in dependence of coded information to be recorded on the document, obtaining a timing signal from the light sensors in dependence of the light modified by the markings, with the aid of the timing signal, serially reading out the coded information from the marking portions remaini

Abstract: There is described a process for embossing onto a document machine-readable information in the form of optical markings with a light-modifying relief structure for indicating the genuineness of the document, comprising transferring a thermoplastic layer to the document from an embossing foil by means of a hot embossing die, and simultaneously embossing the optical markings in at least the thermoplastic layer. Also described are embossed documents produced by the disclosed process.

Abstract: An optical reading apparatus is described for reading documents which contain information in the form of optical markings which deflect a reading beam coming from a light source in at least one given direction of deflection. A first light sensor detects a deflected partial beam. A second light sensor, the optical axis of which lies in a given direction of deflection, is only receptive to those light rays deflected at the document which lie outside a first cone and inside a second cone which is coaxial with the second light sensor. A comparator compares the electrical signals of both light sensors. Altered markings, which cause additional dispersion of the reading beam, can be reliably distinguished from the unaltered markings.

Abstract: A process for the protection of electrical systems upon return of power after power interruptions, through the immediate disconnection of secondary consuming units by an audio-frequency control receiver, and the subsequent reconnection thereof in timed sequence. The audio-frequency control receivers have, in addition to a normal control path, a second path, through which, upon return of the voltage, the switch relay for secondary consuming units is disconnected upon reaching 2/3 of the system voltage. The process may be implemented through the use of a two-state D.C. relay, which is controlled by a secondary path including a cold lead to the system voltage. The process may alternatively be implemented through the use of a two-state A.C. relay which is controlled through a half-wave secondary path including a capacitor/resistor parallel circuit.

Abstract: A circuit arrangement for a keyboard is disclosed, in which the switches of the keyboard are each connected in series with a respective LED to form a switch matrix, the rows of which are connected to a multiplexer and the colums of which are connected to an evaluation device. The LED's serve as decoupling diodes, and furthermore form a diode matrix of an optical indication field by which the commands entered into the keyboard through activation of its switches, or other information, can be made optically visible. Upon activation of a transistor switch, a resistor is switched parallel to a measurement resistor, whereby an LED is lighted at the point of intersection of the activated matrix row and matrix column.

Abstract: There is disclosed a method for embossing a relief pattern of high resolution into a thermoplastic information carrier by means of a heatable embossing matrix. The matrix, which exhibits the desired relief pattern, is pressed onto the thermoplastic information carrier, and is then heated by means of an electric current. After the electric current has ceased, the embossing pressure is maintained until the thermoplastic information carrier has hardened through cooling. Alternative methods permits selected variation of the relief pattern to be embossed by selectively altering the surface of the support member which supports the information carrier during the embossing operation or by selectively heating the embossing matrix.

Abstract: A method and device for identifying documents. A multiplicity of machine-readable markings which characteristically modify incident light by diffraction or refraction are applied to the documents, and selected markings are then cancelled out, the remaining markings representing coded information. The markings are of at least two different kinds causing different modification of incident light, and are arranged in a characteristic configuration on the documents. Information about said configuration is stored in an identification device to permit checking of the remaining markings.

Abstract: There is disclosed a document comprising a flat support member of non-thermoplastic material at least partly coated with a thermoplastic coating, in which coating are embossed optical markings having a light-modifying relief structure, said markings representing information indicating the genuineness or identity of the document. There is also disclosed a process for producing such a document, and an embossing die for use in such a process.

Abstract: Apparatus for storing and reading data in association with a card which has a timing track comprising at least three different kinds of optically-readable timing markings arranged in the timing track in a cyclic sequence, and a data track, the apparatus including three optical timing sensors respectively responsive to the three different kinds of timing markings, and a reading direction detector controlled by the timing sensors.

Abstract: A document is disclosed, which comprises an information carrier in which information is recorded as optical markings. The information carrier has a shape-memorizing capability actuated by supplying energy, such as heat, which changes the shape of the information carrier and the optical markings.

Abstract: There is described a method of producing a document coded with machine-readable information, said document having an information carrier with a multiplicity of storage positions, wherein selected storage positions are occupied by respective machine-readable optical markings, which markings cause a predetermined modification of incident light; the geometrical position of the markings on the information carrier represents coded information. In the method disclosed, such an optical marking is introduced into each storage position, and subsequently, selected optical markings are cancelled or altered. Also described are documents coded by means of the disclosed method, as well as a device for cancelling or altering the optical markings.

Abstract: An apparatus for impressing relief patterns of high resolution, particularly phased holograms or phased diffraction gratings, in a thermoplastic information carrier, comprises a heatable impressing matrix in strip form, which carries the relief pattern and which, together with the information carrier, is passed between two calender rollers, the impressing matrix being adapted to be heated by a current flowing through it.