Abstract: A method and system for evaluating output signals from at least one sound pickup of a security alarm system and for generating an alarm signal by performing the following operations: before the system is placed into operation, determining a first signal frequency range containing the frequency of a signal to be determined and a second signal frequency range containing the frequency of an interference signal; then, during operation, filtering the two frequency range components out of the sound pickup output signals, each component containing a respective one of the frequency ranges, comparing the amplitudes of the two frequency components to one another and generating a difference signal representative of the difference therebetween, and generating an alarm signal whenever the difference signal traverses a threshold value.

Abstract: A power switch in which an arc is produceable in an arc area between electrodes which are moved apart upon opening the switch comprises a fixed electrode forming one electrode for the power switch and a movable electrode forming the other electrode of the power switch movable into and out of contact with the fixed electrode. A space is produced between the fixed and movable electrodes which forms an annular arc area. A magnetic field producing coil is positioned annularly about the arc area and is energized to form a magnetic field when the movable electrode is disengaged from the fixed electrode to produce a rotation of the arc formed between the two electrodes in the annular arc area. A driving device is connected to the movable electrode for moving it away from the fixed electrode and the movable electrode includes a piston portion which is movable into a compression chamber. The compression chamber includes at least one bore directed toward the annular arc area.

Abstract: A dynamic electroacoustic transducer includes a moving coil which is arranged in an air gap between a pole piece and a pole plate which is filled with a magnetic liquid. At least the outside of the coil has a smooth surface in contact with the magnetic liquid. The coil may also advantageously be wound on a carrier from a wire which is flat at least on one side so that this flat side is turned outwardly and presents a smooth continuous surface. The cross-section of such a wire may advantageously be rectangular. The coil may be coated on its outside surface with a foil of well-conducting material, such as aluminum, or the grooves between a cylindrical coil, for example, may be filled with a lacquer or the like.

Abstract: A circuit for controlling a current source transistor in dependence on a d.c. supply voltage comprises a further current source connected to the d.c. supply voltage source, and supplying a component with current, the control voltage for the current source transistor dropping across the component and a resistor controllable in dependence in the d.c. supply voltage and connected in parallel with the component.

Abstract: In apparatus for the separate discharge of flat items from a stack of such items, which apparatus includes a movable support for supporting the stack of items, a withdrawal mechanism mounted to engage the foremost item in the stack and withdraw that item from the stack, a supporting wall manually movable into an initial position for supporting the trailing end of the stack, and a drive system connected to drive the supporting wall toward the withdrawal mechanism under control of the state of a switch actuated in dependence upon the force being exerted by the stack on the withdrawal mechanism, resilient force equalizing elements are provided between the drive system and the supporting wall in drive transmitting relation therebetween, and are constructed and mounted for permitting advancing movement of the supporting wall to lag behind that corresponding to the sum of the drive movements produced by the drive system whenever the pressing force between the supporting wall and the stack exceeds a given value.

Abstract: An electronic switch for converting a pulse signal into a continuous analog signal by connecting a d.c. voltage to an integrating circuit under the control of pulses of the pulse signal comprising two switching elements connected by a voltage divider, and lying between the poles of the d.c. voltage source, the divider ratio being selected to compensate the effects on the analog output signal at the output of the integrating circuit of temperature dependence of the switching elements.

Abstract: In a process for producing an electrophotographic recording material composed of a double layer of amorphous and crystallized selenium on an electrically conductive carrier, a layer of tellurium having a thickness of 10 to 500 nm is applied onto the surface of the carrier, and selenium is then vapor-deposited onto the tellurium layer to a thickness of 20 to 100.mu. to form the double layer.

Abstract: Plastic surfaces are activated for the reception of adherent metal coatings by depositing noble metal nuclei thereon, the noble metal nuclei being deposited by a multistep process including the steps of mechanically roughening the surface, treating the roughened surface with a complex-former solution, thereafter treating the surface with a solution of a noble metal complex salt so as to exchange the noble metal complex for the complex deposited by the initial complex-former solution, and converting the noble metal complex to form metal nuclei.

Abstract: In a method of manufacturing a semiconductor/glass composite material, a glass substrate is covered partially by a covering layer, a semiconductor is connected by pressure and heat to the surface of the substrate not covered by the covering layer, and the semiconductor is then etched away by means of etch polishing to the thickness of the covering layer. The covering may be silicon dioxide, and may be applied to substrate by sputtering or by deposition from the gas phase. The etching solution is NH.sub.4 OH and H.sub.2 O.sub.2 in the ratio 700 to 1.The composite material may be used as a photocathode in an image converter or image intensifier tube.

Abstract: In order to control a power semiconductor which can be triggered into conduction by pulses of one polarity and quenched again by pulses of the opposite polarity, by transmitting such pulses via a transformer to the power semiconductor connected at the secondary side of the transformer, such a pulse is formed by turning on a first transistor connected between one pole of a voltage source and a tap which divides the primary winding of the transformer into two partial windings, and by selectively turning on either one of second and third transistors each connected to the ends of a respective partial winding, and such a pulse is terminated by switching off the first transistor, while maintaining on the selected second or third transistor in order to cause the demagnetization current of the transformer to flow through the selected transistor and through a Zener diode connected between the tap of the primary winding and the other pole of the voltage source, the anode side of the first Zener diode being connected to

Abstract: A solar cell arrangement comprises a first plate or disc of light transmissive material, one side of the first plate or disc having a structure of light transmissive elevations tapering parabolically and cut off parallel to the surface of the plate or disc at the level of their focal points or lines, the structure having a layer of at least partially light transmissive electrically conductive material on the surface of the elevations and a second plate or disc of semiconductor or metallically conducting material, the plate or discs being assembled together to provide photo voltaic and electical contacts between the said cut off surfaces, of one plate or disc and the surface of the other plate or disc such that light passing through the first plate is concentrated at the contacts.

Abstract: A digital phase control circuit which includes a controllable oscillator, a programmable divider coupled to the oscillator, a reference frequency source, a phase discriminator coupled to the outputs of the programmable divider and reference frequency source and means coupling the output of the phase discriminator to a control input of the oscillator. In addition to these components, an auxiliary circuit is provided which has its input coupled to the output of the phase discriminator and first and second outputs coupled to the reference frequency source and the programmable divider. The auxiliary circuit generates a first signal at the input of the reference frequency source when the phase difference between the signals at the outputs of the programmable divider and the reference frequency source is in one direction and a second signal at the second input of the programmable divider when the phase difference is in the opposite direction.

Abstract: A constant current switch for controlling a generally constant switchable load current with fluctuating voltage comprises a first transistor connected in to the current branch of the load circuit and having a voltage divider in parallel to its control path for measuring its control voltage and a second transistor connected to the control input of the switch and to the voltage divider.

Abstract: A solid state circuit which has a plurality of integrated circuit elements, each having at least a pair of connecting terminals. The operability of the individual elements is determined by providing an arrangement including an insulating layer on the solid state circuit, this insulating layer having arranged on it the pairs of terminals of the individual elements with the insulating layer insulating all of the terminals from each other. At least one further layer is arranged on the insulating layer and covers at least the respective pairs of terminals of the elements. This further layer has, at least in the region where it covers respective pairs of element terminals, optical characteristics which are selectively variable in dependence on the potential difference between the pairs of terminals of each respective element. The arrangement may be used as a picture producer, converter or amplifier.

Abstract: An interference-potential-compensated thyristor comprising, a common emitter zone of one conductivity type, a common main base zone of an opposite conductivity type in contact with said common emitter zone, a common control base of said one conductivity type in contact with said common main base, first and second outer emitter zones of said opposite conductivity type in contact with said common control base, a common metallized electrode layer in contact with said common emitter zone, a first opposite metallized electrode layer in contact with a portion of said common control base and said first outer emitter zone at a junction between said common control base and said first outer emitter zone, and a second opposite metallized electrode layer in contact with a portion of said common control base and said second outer emitter zone at a junction between said common control base and said second outer emitter zone, said first outer emitter zone defining a pilot thyristor part thereabout and said second outer emit

Abstract: A fast switching thyristor having a shorted emitter structure in which, in order to shorten the turn-off time, the charge carrier lifetime is set to be low by means of recombination centers. The charge carrier lifetime in at least the control base zone of the thyristor is set initially to be homogeneous and low corresponding to a desired firing resistance underneath the emitter zone with respect to the voltage rise of the returning forward voltage in the thyristor after every recovery process, and the charge carrier lifetime is set to be low compared to the homogeneous setting in the partial region of the control base zone extending from below the control electrode substantially to the portion of the edge of the emitter zone which faces the control electrode but without contacting the edge of the emitter zone.

Abstract: A method of epitaxial deposition comprises arranging semi-conductor discs and source material in two spaced planes in a reaction vessel, controlling the temperatures of the source material and the semi-conductor discs separately and introducing a gaseous medium into the reaction vessel to provide an equilibrium condition in which material is moved from the source material and deposited on the semi-conductor discs.The invention also includes an apparatus suitable for carrying out the method.

Abstract: In a semiconductor laser composed of a sequence of layers forming a heterostructure diode and including a substantially homogeneously doped layer defining a laser active zone having a laser radiation exit face perpendicular to the layers, the current flowing in the forward direction of the diode is constricted to a narrow, strip-shaped region in the laser active zone by providing a monocrystalline layer located in the layer sequence to be spaced from the active zone by at least one intervening, doped semiconductor layer, providing the surface of the monocrystalline layer directed away from the active zone with a trough-shaped recess extending essentially perpendicularly to said radiation exit face, and diffusing, via the surface provided with the recess, and toward the active zone, doping material which produces a doped region of same conductivity type as the intervening, doped layer, the doped region being delimited by a diffusion front substantially parallel, and corresponding in contour, to the surface pro

Abstract: In a circuit for automatic dynamic compression or expansion the control voltage generator generates a control voltage which is linear against the logarithm of the input amplitude. This characteristic is achieved by a transfer member consisting of several transistors which are subject to different reference voltages and the series resistances of which are staggered.

Abstract: A radio system composed of a transmitter and an associated receiver in combination with a data transmission device and an associated voice instrument. Service channel signals operating at a frequency at the lower end of the system base band are conducted by a service channel apparatus composed of separate service channel networks for the transmitter and data transmission device connected to the service channel connections thereof. The service channel networks are connected to a common bus bar.