Abstract: A ballast for powering a high intensity discharge lamp including an ignitor and a resonant circuit. Ignition pulses produced by the ignitor are added to a boosted low frequency voltage produced by the circuit operating near its resonant frequency during start up of the lamp. The circuit is disabled after a predetermined period of time has elapsed following ignition of the lamp. Application of the signal precedes application of the ignitor pulses to the lamp. Disablement of the circuit can render the ignitor inoperable.

Abstract: A ballast for a high intensity discharge lamp which detects the onset of acoustic resonance instability by detecting an asymmetry in a signal which is otherwise symmetric in the absence of such instability. The AC supply ripple voltage, which is normally present in the lamp current, exhibits symmetry in the absence of acoustic resonance, and becomes substantially asymmetric at the onset of acoustic resonance. By measuring the duration of each half cycle in the ripple voltage, an asymmetry in the ripple voltage can be easily and rapidly detected, and the operating frequency of the lamp current is changed before the resonance produces visually apparent flicker.

Abstract: A circuit arrangement is provided with a controlled switch which is controlled by means of a periodic switching signal for operating an oscillation circuit at a frequency f, and with a control circuit for generating the periodic switching signal. The control circuit comprises a pulse width generator for generating a periodic square wave signal with a half cycle duration which is adjustable in steps of a value T and which has a value of at least t. The circuit arrangement is characterized in that, with 2*(t+N1*T)<1/f<2*(t+(N1+1)*T) in which N1 is an integer number, the periodic switching signal is built up from a repetitive chain of square wave signals with a repetition cycle which comprises n1 half cycles of a duration t+N1*T and n2 half cycles of a duration t+N2*T, wherein N2 is >N1 and is an integer number.

Abstract: Information is extracted from a hand-written text by means of a graphics tablet (1). The curves thus obtained make it possible to recognize primitives, namely basic forms, representing a way of writing a part of a letter. More accomplished forms, called allographs, are constructed from primitives in order to construct a letter or in even a group of two or three letters. When the series of codes corresponds to a known object from a dictionary of allographs (3), each defined by the sequence of codes of its primitives, the corresponding allograph is recognized. The genetic algorithm is used to improve the population of strings. "Descendants", obtained by combining two starting strings (7), are constructed from a limited-quantity selection of strings (9), from among which descendants the most appropriate are in turn chosen, this gradually optimizing the population. Applications: recognition of cursive writing.

Abstract: A circuit arrangement for igniting and operating a high-pressure discharge lamp is provided with a switching device, inductive device and a rectifier which together form a Buck converter, connected to input terminals for connection to a supply source and output terminals for connection of the lamp. The lamp is supplied with a current through periodic switching of the switching device alternatively into a conducting and a non-conducting state by means of a switch-on and switch-off signal, respectively. The inductive device includes a primary and a secondary winding with the secondary winding forming part of an integration network for generating the switch-off signal. The secondary winding also forms part of a voltage divider network for generating the switch-on signal. A very simple circuit arrangement is thereby achieved.

Abstract: An electronic ballast for a fluorescent lamp includes a delay triggered circuit which, upon expiration of a predetermined period during which the lamp filaments, constituting opposite electrodes of the lamp, are preheated, applies high frequency operating voltage across the opposite electrodes of the lamp beginning with a transition from a condition of no voltage to a condition of full rated voltage which occurs within one cycle of the high frequency voltage. The sharp transition from zero "glow current" to full "arc current" at the end of the preheating period has been found to increase the life of lamps in the number of on-off starts, particularly with respect to lamps of poor quality. The rapid transition is possible because the ballast uses the same inverter and transformer for supplying preheating and operating voltages. The operating voltage is applied between the opposite electrodes of the lamp via an electronic bi-directional switch, controlled by a preheating delay RC timing circuit.

Abstract: A circuit arrangement for the high-frequency operation of a discharge lamp comprises a first rectifying circuit (D1-D4) for generating a DC voltage across a first capacitor (C1) from a low-frequency supply voltage. A DC/AC converter (IV) for generating a high-frequency AC voltage at a frequency f from the DC voltage is coupled to a load branch (B) provided with coupling means (T3, T4) for coupling the discharge lamp (Li) to the load branch. The load branch connects a junction point N1 of the DC/AC converter to a junction point N2 between the first rectifying circuit and the first capacitor. A second rectifying circuit for converting a high-frequency voltage generated by the DC/AC converter into a DC voltage is coupled to the first capacitor and to a junction point N3 in the load branch. A control circuit controls the power consumed by the discharge lamp through variation of the frequency f. The coupling means are connected between the junction point N2 and the junction point N3 in the load branch.

Abstract: A motor with reduced radial forces includes a first motor part made up of 2P permanent magnet poles surrounding a second motor part formed by a magnetic yoke having a number T of pole teeth and with an air gap between the first and second motor parts. The first and second motor parts are moveable relative to one another. Exciter coils are mounted on the pole teeth and the pole teeth are separated by pole gaps. For a motor with a number 2P magnet poles and a number T of pole teeth which do not have a common submultiple greater than 1, each of the pole teeth have a centrally located auxiliary slot facing the air gap thereby to reduce undesirable radial forces.

Abstract: A lighting unit comprises an electrodeless low-pressure discharge lamp (10) and an electric supply (60) for the lamp. The lamp is provided with a discharge vessel (20) having a radiation-transmitting enveloping portion (21) and a recessed portion (24). The discharge vessel encloses a discharge space (27) in a gastight manner and contains an ionizable filling. The lamp also is provided with a coil (30) positioned in the recessed portion for generating a high-frequency magnetic field so as to maintain an electric discharge in the discharge space. The enveloping portion (21) of the discharge vessel is provided with a radiation-transmitting, electrically conducting layer (22) at a surface facing the discharge space (27). This layer is electrically connected to a lead-through member (42) which issues to the exterior of the discharge vessel. The lead-through member is a metal tube which forms at least a portion of a tubular projection (46, 42, 47).

Abstract: A circuit arrangement for operating a discharge lamp comprising an oscillator for generating a high frequency input voltage and a piezo-electric transformer with input terminals coupled to the oscillator and output terminals. A load circuit is coupled to the output terminals of the piezo-electric transformer and includes terminals for lamp connection. The load circuit comprises an adjustable capacitor which forms a very simple device for controlling the light output of the discharge lamp over a wide range.

Abstract: The invention relates to a circuit arrangement for igniting and operating a high-pressure discharge lamp provided with a control circuit which limits the voltage to a value Vb across the output terminals of the circuit arrangement such that:Vla<Vb<Vi.wherein Vla is the nominal lamp voltage and Vi is the threshold voltage across the output terminals at which the ignitor starts.

Abstract: Source separation system for processing input signals (E.sub.i (t)) formed by instantaneous linear mixtures of primary signals (X.sub.j (t)) that result from sources (S1-Sn) and for producing at least one estimated primary signal (x.sub.k (t)) . The system includes separation apparatus (10) and characterization apparatus (15) which determine cumulants of the input signals for extracting estimated mixing coefficients (.alpha..sub.ij). The coefficients are transformed into separation coefficients (C.sub.ki, d.sub.ki) in the separation apparatus (10). The separation apparatus (10) may have a direct structure or a recursive structure.

Abstract: A method for installing a wireless network, which includes the steps of physically installing a plurality of nodes in respective different locations in a building, connecting the nodes to a power supply and powering up the nodes, using a wireless installation device to program a respective address into the nodes, using the wireless installation device to program one or more default settings into the nodes, using the wireless installation device to verify operation of the nodes, and, using the wireless installation device to dump at least information regarding the physical location and associated address of the nodes to a building computer. In a presently preferred embodiment, the wireless installation device is preferably an RF portable computer which has an RF transmitter which has a variable power setting, and an RF receiver which also has a variable power setting.

Abstract: An AC-AC ballast system for a discharge lamp (e.g., a fluorescent lamp), which includes a PFC converter which incorporates an isolation transformer, and a DC-AC inverter provided on the secondary side of the isolation transformer. Because the AC line input is isolated from the lamp load by the transformer in the PFC converter, the switching frequency of the PFC converter can be advantageously significantly higher than the lamp current frequency (and the switching frequency of the DC-AC inverter), to thereby enable a significant reduction in the size and weight of the ballast system, without an increase in the emission of EMI radiation from the lamp. In this regard, the ballast system of the present invention can be thought of as a two-frequency ballast system having an isolated PFC converter.

Abstract: A circuit arrangement for igniting and operating a discharge lamp (1) comprising inductive means, which include a primary winding (PRIM) which passes a high-frequency current during ignition and during lamp operation, and a secondary winding (SEC) which is magnetically coupled to the primary winding and electrically coupled to an impedance M (C1, C3) for limiting the current passed by the secondary winding. The current through the secondary winding generates a DC voltage via rectifying means, by which current a part of the circuit arrangement is supplied. The circuit arrangement is also provided with apparatus X (R, S1) for increasing the impedance value of the impedance M after ignition of the discharge lamp. The amplitude of the DC voltage is thereby at a desired level both before and after ignition of the discharge lamp, while no major power dissipation takes place during stationary lamp operation.

Abstract: In a multimedia system, such as a video-on-demand server, a file with data is stored in a series of successive clusters which may be distributed across the disc. A cluster consists of physically successive sectors which can be read in blocks by a user application. By repeating a part of the data at the end of a cluster at the beginning of the next cluster, the system enables reading of a block of sectors from an arbitrary sector, said block and the subsequent blocks nevertheless being accessible by way of one seek operation. The interactive response time is thus substantially improved in situations in which the user requests an arbitrary data fragment.

Abstract: A display device is provided with a window frame (7). This window frame is arranged on the front wall (2). A vacuum-tight connection (10) is formed between the window frame and the front wall, and between the window frame and a rear wall (3) or a projecting portion of an intermediate element (4). The window frame reduces the risk of leakage, reinforces the construction and makes possible an improved method of manufacturing the display device.

Abstract: In a multiphase motor driver, each phase current is controlled by the ratio of measurements across a common sense element. By utilizing the same sense element for each phase, inaccuracies which result from the variance among multiple sense elements can be eliminated. The individual phase currents are controlled from a common clock generation device. By appropriately controlling each of the phase currents to assure that only one of the phase currents is flowing through the sense element at the time of measurement, the measurement is assured to be dependent on the individual current and the parametric value of the sense element only. Thereby, the control of the phase currents, via the ratio of the measured values across the common sense element, is independent of the parametric value of this common sense element.

Abstract: Data rate and robustness of digital error protection is improved according to the method and device of the present invention to obviate the need for audio interpolation and consequently, to be useful in fields where audio interpolation cannot be done without complex encoding and decoding strategies. Digital information signals are transferred in the form of a plurality of a number of sequences of information symbols. Each information symbol has a uniform bit length and each sequence of information symbols occurs in a respective input channel. Check words are included in transmitted digital information signals and are encoded to allow correction of erroneous symbols caused on transmission.

Abstract: A communication method particularly suited for lighting control employs encoding of perturbations in a voltage signal having a fundamental period with a nominal waveform. A control period includes a pre-selected number of fundamental periods of the voltage signal. Different control commands are indicated by imposing a selected perturbation, such as a phase cut, on the nominal waveform with a respective occurrence signature within the control period. The control commands are decoded from the voltage signal by detecting the occurrence signature of the perturbations within each control period. Decoding is accomplished by differentiating the nominal waveform to detect encoded perturbations.