Abstract: The present invention relates to a process for preparing polyisocyanates containing allophanate groups by reacting compounds a), whichi) contain urethane groups, but which are substantially free of hydroxyl groups and isocyanate groups,ii) have an average of at least two urethane groups per molecule,iii) are prepared by reacting organic isocyanates a1) with organic hydroxyl compounds a2) andiv) have an average molecular weight of at most 2,500,with excess quantities, based on the urethane groups, of distillable organic polyisocyanates b) to form polyisocyanates containing allophanate groups and subsequently removing by distillation the unreacted excess of component b) to a residual content of less than 0.5 wt. %, provided that polyisocyanates a1) and polyisocyanates b) are different.The present invention also relates to the products obtained from this process and to their use as binders or binder components in coating compositions.

Abstract: A process for preparing liquid lacquer polyisocyanates with aliphatically and aromatically bound isocyanate groups and an NCO content of 5 to 25 wt. % by trimerizing an isocyanate component A), containing A1) 70 to 100 wt. % of diisocyanatotoluene and A2) 0 to 30 wt. % of other aromatic isocyanates and B) aliphatic lacquer polyisocyanates, optionally with prior, simultaneous and/or subsequent reaction of a portion of the isocyanate groups with an alcohol component C) having a molecular weight of 32 to 900, and optionally in the presence of D) inert solvents; the resulting lacquer polyisocyanates; and their use in coating compositions, in particular as a cross-linking agent for polyhydroxyl compounds in two-component polyurethane coating compositions.

Abstract: A process for the production of olefinically unsaturated isocyanates by reacting a1) isophorone diisocyanate or mixtures of isophorone diisocyanate with a2) other organic polyisocyanates with b1.1) olefinically unsaturated carboxylic acids or mixtures thereof with b1.2) other monobasic or polybasic carboxylic acids, b2.1) olefinically unsaturated alcohols and/or b2.2) other monohydric or polyhydric alcohols, the unsaturated resulting isocyanates and their use as binders for one-component coating compositions which may be cured at room temperature.

Abstract: Water-dispersible polyisocyanate compositions based on aliphatic and aromatic diisocyanates and having an NCO content, based on solids, of 6 to 21% by weight, a weight ratio of incorporated TDI units to incorporated HDI units of 6:1 to 0.1:1 and a content of ethylene oxide units, arranged within terminal polyether chains, of 5 to 40% by weight; a method for the preparation of these polyisocyanate compositions by reacting a polyisocyanate component with monovalent polyether alcohols containing ethylene oxide units at an NCO/OH equivalent ratio of 2:1 to 120:1; and aqueous coating compositions containing these polyisocyanate compositions and polyhydroxyl compounds as the binder.

Abstract: The present invention relates to a process for the production of storage stable prepolymers containing free isocyanate groups by reactinga) an organic polyisocyanate component having (cyclo)aliphatically bound isocyanate groups and a maximum functionality of 4.5 withb) one or more hydroxy-functional polyacrylate resins having a content of alcoholic hydroxy groups of 0.05 to 7% by weight at an equivalent ratio of isocyanate groups of component a) to hydroxyl groups of component b) of 3:1 to 40:1, wherein components a) and b) are selected to provide a value B of at most 4 when calculated in accordance with the formula: ##EQU1## wherein F.sub.1 and F.sub.2 represent the NCO and OH functionalities of components a) and b), F.sub.1 representing the component with the lower functionality when the components differ in functionality andval.sub.A /val.sub.I represents the OH/NCO equivalent ratio of components a) and b).

Abstract: A switching device is presented for the transmission of telecommunication signals between a telephone network exchange and at least one subscriber connected thereto, where the exchange is able to transmit metering pulses, in addition to the voice signal. The signals are transmitted as digital signals between the exchange and the subscriber via a two-wire line, Which is connected with the exchange through a hybrid switching unit. To prevent the metering pulses from interfering with the voice signals, a parallel resonant circuit consisting of an inductance and a capacitor is connected to the two-wire system of the hybrid switching unit, and the receiving branch of the hybrid switching unit has an active and a passive filter connected in series. The passive filter is adjusted for the metering pulse frequency, and a filter that is tuned to the passive filter is used as the active filter, which compensates for a decrease in the NF (low frequency) level caused by the passive filter, with a corresponding increase.

Abstract: A water-dispersible polyisocyanate composition obtained by the partial urethanization of the isocyanate groups of 2,4- and/or 2,6-diisocyanatotoluene with monohydric and polyhydric alcohols, a process for its production, its use as the binder for an aqueous two-component coating composition in combination with a water-soluble or water-dispersible polyhydroxyl component and coatings for water-resistant sheet-form substrates prepared from this coating composition.

Abstract: The present invention relates to olefinically unsaturated, urethane group-containing isocyanates which are prepared by reacting at an NCO/OH equivalent ratio of 4 to 40a) an isocyanate component substantially containing urethane group-free cycloaliphatic diisocyanates withb) an unsaturated alcohol component substantially containing monohydric olefinically unsaturated alcoholsand subsequently removing distillable unreacted isocyanates by distillation. The present invention also relates to a process for the preparation of these isocyanates and to their use as a binder component in one-component, coating compositions which may be cured at room temperature.

Abstract: The present invention relates to a process for the production of polyhydroxyl compounds having a hydroxyl group content of 2 to 10% by weight and a viscosity at 23.degree. C. of 250 to 80,000 mPa.s by the radically initiated polymerization at a reaction temperature of 80.degree. to 220.degree. C. ofa) 100 parts by weight of a mixture of olefinically unsaturated monomers containing at least 1% by weight of monomers containing alcoholic hydroxyl groups in the presence ofb) 5 to 500 total parts by weight, which may be present at the beginning of the reaction or added during the reaction, of one or more cyclic compounds which, in the presence of initiator compounds containing alcoholic hydroxyl groups, are capable of a ring-opening polymerization reaction andc) 2 to 300 parts by weight, which may be present at the beginning of the reaction or added during the reaction, of one or more polyhydric alcohols having a molecular weight of 62 to 1000.

Abstract: A process is indicated for the bidirectional transmission of digital data through a glass fiber, whereby the bits from data to be transmitted are compressed by a factor >2 into bursts, in packages of equal quantities, without changing the transmission rate. The bursts in one direction of the transmission are sent by an emitter station through a glass fiber to the other station, during the pauses between the bursts in the other transmission direction. Independent external pulse generators are used at both ends of a glass fiber to determine the transmission rates of the stations. If the frequencies of the two pulse generators deviate from each other, the bursts of the data flowing at the lower transmission rate are displaced with respect to the bursts of the other flow of data, by the width of one bit of the pertinent continuous flow of data.

Abstract: A connecting line is provided between a switching center and a subscriber for transmission of telecommunication signals. At the subscriber's end of the connecting line, there is located a device which, in addition to other passive and active units, includes a transformer, whose output winding is subdivided into two partial windings of identical size. A first capacitor, a switch and a second capacitor are connected in series between the partial windings. To prevent distortions of the dial pulses, a connecting line between the switch and the second capacitor is connected with a reference potential of the circuit arrangement.

Abstract: In a system wherein a main channel of data is transmitted between two stations by means of an optical waveguide, an additional optical channel may be transmitted. Bits of the additional optical channel are inserted into the main channel at a transcoder in the transmitting station in place of bits of the main channel at defined spacings, known to the transcoder of the receiving station, with a bit rate lower than that of the main channel. The inserted bits are removed from the optical main channel at the receiving station. The bits of the additional optical channel inserted into the main channel are double bits that are identical to a forbidden bit combination that results during the recoding of an electrical AMI code into an optical CMI code. In the receiving station, the double bits of the main channel replaced by the bits of the additional optical channel are recovered by using sequential logic and memory to apply the fixed rules of the electrical AMI code.

Abstract: A controllable amplifier, which has two symmetrical outputs, at which two output signals mirror-symmetrical with respect to each other are present, is used for amplification of a burst signal. To achieve the largest possible eye opening of the signals to be fed to a comparator, a predetermined d.c. voltage difference for the formation of matched signals is adjusted for both output signals. After this, the arithmetic mean values of the two matched signals are formed and are fed to a second comparator. The output value of the second comparator is fed to an integrator, to which a reference voltage is also fed. In case of a deviation of the mean values of the two matched signals from each other, the amplifier is adjusted in a compensating direction by the integrator.

Abstract: For controlling the level of electrical signals a circuit arrangement is formed with two series connected amplifiers. A first amplifier containing a first variable resistor, operates at maximum amplification when a low input signal level is received. A second amplifier comprises a series connection of a second variable resistor and a current-controlled voltage source with two complementary outputs. The outputs of the voltage source are connected to a comparator and a controller with two separate outputs. One of the controller outputs transmits a control signal while the other output simultaneously transmits a blocking signal. A first output of the controller is connected with the first variable resistor, while a second output of the controller is connected to the second variable resistor.

Abstract: Apparatus for bidirectional transmission of optical signals between two stations connected by a light transmission path of optical fibers, each station including a laser module comprised of a laser diode and an adjacent monitor diode, the latter performing the dual functions of detecting light emitted by such laser diode in its transmission mode, and for detecting light transmitted from the other station when such adjacent laser diode is not in its transmission mode.

Abstract: This invention relates to a process for preparing polyurethanes having liquid crystal properties comprising reacting, in proportions corresponding to an NCO/OH equivalent ratio of from about 0.9:1 to 1.1:1, an organic polyhydroxyl compound with an organic diisocyanate having at least two phenylene groups and at least one carboxylic ester group. The organic diisocyanate comprises an aliphatic diisocyanate wherein at least one of the carboxylic ester groups connects an aliphatic group to a phenylene group or an aromatic diisocyanate wherein at least one of the carboxylic acid groups connects two phenylene groups.This invention further relates to preferred diisocyanates used in the process according to this invention.

Abstract: There is disclosed an improved method and apparatus for operating an electric power station including a cycled transformer having a primary winding and a plurality of secondary windings, in a manner that includes the changing of the current permeability of a variable load component connected in parallel to one of the secondary windings for preventing the current flowing within the circuitry thereof from decreasing below a predetermined value during a no-load condition at the output terminal of such secondary winding, thus assuring that the widths of the direct current pulses admitted into the primary winding are maintained above a predetermined value and that the energy transfer to each of the secondary windings is sufficient.

Abstract: This invention relates to a process for preparing polyurethanes having liquid crystal properties comprising reacting, in proportions corresponding to an NCO/OH equivalent ratio of from about 0.9:1 to 1.1:1, an organic polyhydroxyl compound with an organic diisocyanate having at least two phenylene groups and at least one carboxylic ester group. The organic diisocyanate comprises an aliphatic diisocyanate wherein at least one of the carboxylic ester groups connects an aliphatic group to a phenylene group or an aromatic diisocyanate wherein at least one of the carboxylic acid groups connects two phenylene groups.This invention further relates to preferred diisocyanates used in the process according to this invention.

Abstract: A circuit for protecting electronic devices which are fed from a source of dc voltage and to which a subscriber's line (ASL) is connected. In order to limit the current in the event of an overload on the subscriber's line (ASL), a MOSFET (T1) is provided as current-limiting component. The MOSFET (T1) is disconnected and re-connected periodically by means of a relaxation generator (K) when the MOSFET is in its current-limiting condition. Upon the normal operation of the circuit, the relaxation generator (K) does not operate. By proper dimensioning thereof, the time for which the MOSFET (T1) is blocked can be roughly adjusted as compared with the time in which it acts as current limiter. In this way, too great a heating of the MOSFET (T1) is avoided.

Abstract: A circuit is described for producing an alternating voltage in an electronic device which is remotely fed over a digital transmission path. By the pulses of a clock (8) two capacitors, C1, C2 are charged via a transistor (T1) and a transformer (10), one of them (C2) being discharged over a parallel resistor (R2). A coupling capacitor (CK) which is charged by the other capacitor (C1) is discharged alternately by the influence of the dischargeable capacitor (C2) over a transistor (T2).