Abstract: The invention specifies a diode-split high-voltage transformer having a core, a primary winding and a high-voltage winding, which is arranged in chambers of a coil former, in which the chambers with the high-voltage winding lie below the primary winding, a conductive coating is arranged on the surface of the inner cavity of the coil former, and by virtue of a corresponding arrangement and wiring of the chambers, oscillations arising during operation in the high-voltage transformer induce capacitive currents on the conductive coating, the sum of which capacitive currents results approximately to zero. This can be achieved, for example in that by virtue of a symmetrical arrangement and wiring of the chambers with regard to the diodes, the oscillations induce capacitive currents on the conductive coating which occur in pairs with the same amplitude but in antiphase and thereby cancel one another out.

Abstract: Tape recorder having a group of write heads which are arranged like a matrix in rows and columns, with each write head assigned in one row line and in one column line, and having a driver circuit for passing current through the row and column lines. A write head magnetizes a magnetic tape permanently only when its associated row and column lines have currents applied to them causing magnetic fields that reinforce one another in the magnetic tape. A common row return line is provided to which all the row lines are connected and a common column return line is provided to which all the column lines are connected.

Abstract: A wireless telephone system having a plurality of wireless, battery-powered handsets and a base unit, the base unit having a base transceiver. Each handset has a handset transceiver for establishing a wireless link over a shared channel with the base unit via the base transceiver, wherein the base transceiver transmits to a given handset transceiver a forward data message, which contains forward power level information identifying a forward power level at which the forward data message was transmitted by the base transceiver. The receiver receives and locks onto the forward data message. The transmitter transmits to the base transceiver a return data message at a return power level determined in accordance with the forward power level information.

Abstract: A switched-mode power supply with a control loop and a microprocessor has a normal mode and a low-power mode with a burst mode. The microprocessor is connected via an output to the control loop and uses this to control the burst mode of the switched-mode power supply directly. The control loop of the switched-mode power supply monitors, in particular, a secondary output voltage, so that the output of the microprocessor is connected to the control loop, for example via a simple resistor network or a transistor stage. The clock frequency and the duty cycle of the burst mode are permanently stored in the microprocessor and can be defined for the switched-mode power supply directly, for example using TTL logic.

Abstract: A transformer includes a bobbin with spacers extending inwardly from the bobbin and a barrier extending outwardly from the bobbin. A ferrite core positioned within the bobbin is separated by the spacers to provide a controlled air gap. Primary windings wound around the bobbin are separated into series connected windings by the barrier. The barrier is aligned with spacers so as to prevent any wound portion of the primary windings from overlapping the air gap in the ferrite core.

Abstract: The invention relates to a compact and cost-effective diode-split high-voltage transformer for high voltages of, in particular, above 20 kV, in which the high-voltage winding lies in chambers of a coil former underneath the primary winding and which contains elements by which the electric field between the coil former and the core is reduced in order to avoid corona effects. These elements include, for example, a conductive coating of the surface of the inner cavity of the coil former, which coating preferably comprises colloidal graphite. The conductive coating may also be realized by a metallized plastic film which is wound between the core and the coil former. Alternatively, the cavity between the core and the coil former may be filled with a material whose relative permittivity ∈r is distinctly greater than that of air. The use of a larger number of diodes is also possible for reducing the electric field.

Abstract: It is known for a signal-strength detection unit to be used to detect the ratio of the input signal to the wanted signal obtained after it. A disadvantage in this case is that interference elements, which are also amplified, not only corrupt the output signal of the signal-strength detection unit, but can also adversely affect the quality of the wanted signal. The invention is based on the object of providing a method for improving the wanted signal in the receiving unit of a communications system.

Abstract: The mains filter comprises coils with windings which are arranged on substrates, for example conventional thin printed circuit boards, as conductor tracks. A coil can comprise one or more substrates, which are in contact with one another in the case of a plurality of substrates. In the centre, the substrates have an opening through which a core is passed. With an appropriate number of windings, one substrate is sufficient for one winding, so that only one substrate per coil is required for the mains filter. The two substrates for the two coils can be of identical design, in particular, the input and the output for a coil being arranged on a substrate in the region of opposite corners. The core used can be a narrow E/E core or E/I core, so that the space requirement for the filter on a circuit board is very low.

Abstract: The switched-mode power supply comprises a transformer, a switching transistor connected in series with a primary winding of the transformer, a primary-side control circuit and a secondary-side regulating stage. The regulating stage is coupled to a coupling element for transiting a regulating signal from the secondary side to the primary side. A first switch is situated between the control input of the switching transistor and a primary-side operating voltage, and a second switch is situated between the regulating stage and a secondary-side operating voltage, with the two operating voltages being able to be disconnected using a single control signal. In this case, the isolating element transmits both the regulating information for the primary-side control circuit and the turn-off signal for the first switch. If the second switch is turned off by the control signal, the regulating stage and the optocoupler become completely currentless and consume no further power.

Abstract: A synchronous burst mode power supply includes a power converter for transforming an AC mains from a relatively low frequency to a higher frequency, and a gate circuit responsive to the AC mains supply for enabling the power converter (2) to initiate a burst of output pulses at the higher frequency each time the AC mains supply occurs within a predetermined range. In an alternative embodiment, the power supply has a regulating circuit for regulating output from the power converter that includes a current feedback loop to the gate circuit for pre-regulating control of the power converter in response to load variations.

Abstract: A projection system includes a projector for emitting a light beam; a screen and a first medium for converting a linear polarized form of the light beam from the projector to a quasi-circular polarized form of the light beam polarized in a first circular sense. The projector also includes a mirror for reflecting and phase shifting a quasi-circular polarized form of the light beam to a circular polarized sense substantially opposite of that exhibited by the light beam before being reflected by the mirror, and a second medium optically disposed between the mirror and the screen and for selectively converting the light beam between linear polarization and quasi-circular polarization.

Abstract: The present invention relates to a device for illuminating at least one surface, which includes a light source and a reflector in order to focus the light rays emitted by the source. In said device, the focal plane of the reflector lies between the light source and the said surface and it includes, positioned close to the focal plane of the reflector, a means forming a second light source.

Abstract: The invention relates to a modem intended to be connected to a telephone line comprising a device for detecting the busy state, or the acquisition, of a telephone line. The detector includes a means sensitive to the energy supplied by the modem on its input/output (34) which is connected to the telephone line (38). The detector, which supplies a signal preventing the line being acquired if the line is already busy with another appliance, needs no electrical separation between the line and the modem.

Abstract: Circuits for driving a switching transistor (T3) with a driver stage (T2, T4, T5, L1), as are used for example in horizontal deflection stages of television sets or computer monitors, are known in a wide variety of embodiments. The invention specifies a power-efficient and cost-effective circuit of this type which contains a comparator circuit (T1), which monitors the voltage (UC) across the current input of the switching transistor (T3) for the purpose of monitoring saturation by comparing the said voltage with a reference voltage (UR), thereby effecting regulation. The comparator circuit may be realized, e.g. by a simple transistor circuit (T1), the reference voltage (UR) being applied to the control input of the said transistor circuit, the current input of the said transistor circuit being connected to the drive signal (US) of the driver stage, and the current output of the said transistor circuit being connected to the voltage (UC) via the current input of the switching transistor (T3).

Abstract: An apparatus comprises a source of a first signal synchronized to deflection, the first signal including a first portion representative of a retrace interval, means coupled to a first video signal and responsive to a second signal representative of the retrace interval for generating a second video signal having a blanking interval, and, means responsive to a third signal representative of the blanking interval and to the first signal for generating the second signal so as to control the phase of the blanking interval relative to the retrace interval.

Abstract: A step-up coil of a high-voltage transformer for powering a cathode-ray tube comprises windings housed in chambers of a coil former. These windings are made in pairs. The inner end of the first winding of the pair is connected to an electrode of a first diode, the inner end of the second winding of the pair is connected to the electrode of like nature of the second diode, or alternatively, the outer end of the first winding of the pair is connected to an electrode of the first diode, the outer end of the second winding of the pair being connected to the electrode of like nature of the second diode. The inter-winding capacitances of the windings of the pair are thus non-activated, the corollary of this being a decrease in the value of stray oscillations of the output voltages.

Abstract: A head drum for a magnetic tape apparatus includes a stationary lower cylinder and a rotating upper cylinder on which at least one write/read head is securely arranged and interacts with a magnetic tape with an exchange of electromagnetic signals. Also provided are at least one amplifier which rotates together with an upper cylinder and amplifies the signals coming from the write/read head, and a rotating transformer for transferring electrical signals between the stationary lower cylinder and the rotating upper cylinder. Storage means for electrical energy arranged on the rotating upper cylinder is capable of supplying electrical power to all the electronic components rotating together with the upper cylinder. A controller is securely arranged on the rotating upper cylinder for monitoring the charge state of the storage means and controlling the duration of the energy transfer as a function of the charge state.

Abstract: The invention relates to a tracking device in which a position of a coil driven actuator is determined using a sensor coil. A reference signal 12 having a determined voltage and frequency is fed to a driven coil. A position of the coil driven actuator is proportional to a distance between the driving coil and the sensor coil. The sensor coil produces an alternating voltage induced by an alternating magnetic field emitted by the driving coil. The alternating voltage is used to determine the position of the actuator.

Abstract: The switched-mode power supply comprises a secondary winding and four diodes for producing two rectified voltages of the same polarity, one of which can be regulated. A connection of the unregulated voltage has connected to it a variable Zener diode as an error amplifier for transmitting a regulating signal to the primary side. The driver stage provides a pulse-width-modulated square-wave signal for driving the switching transistor which is arranged at a high potential between the operating voltage on the input side and a first connection of the primary winding. The second connection of the primary winding is connected with a Zener diode and provides a stabilized voltage for the driver stage. Arranged between the driver stage and the control electrode of the switching transistor there is a differentiating element which produces positive and negative switching voltages for controlling the switching transistor.

Abstract: A switched mode power supply circuit for a video display apparatus having run and standby modes of operation A run mode power supply provides an output voltage for the video display apparatus during the run mode of operation. A standby mode power supply provides an output voltage for the video display apparatus during the standby mode of operation. A switched mode power supply controller circuit provides drive pulses to the run mode power supply during the run mode and to the standby mode power supply during the standby mode. A snubber circuit of the standby power supply is used to turn off a start-up transistor during the standby mode of operation to prevent power dissipation in a start-up resistor.