Abstract: An optical switching element including two parallel light wave guides, whose opposite walls are mutually separated by a small distance (d), the so-called coupling distance, each constituted by a strip of a semiconductor material formed on a semiconductor substrate having a refractive index lower than that of the guides, these guides each transporting a monomode wave and the switching being initiated by the effect of polarization means applied to the guides, characterized in that the strip constituting one of the guides (G.sub.1) designated as first guide is formed as a first uniform layer on the substrate (1), in that the strip constituting this guide is covered by a uniform intermediate layer (I) of a compatible semiconductor material, having an index lower than that of the guides and having a thickness which forms the coupling distance between the two guides, in that the strip constituting the other guide (G.sub.

Abstract: A control device (30) for controlling the supply of power to the coils (16A, 16B) of a drive motor (3) for a compressor unit of the resonant-piston type (1). The control device comprises a power-supply circuit (44) for energizing the motor coils from a direct voltage source (45), means (46, 47, 48; 46, 60) for determining a measure (P, .phi.), which indicates whether the power consumption of the motor as a function of the frequency of the energizing current is at least approximately maximal, and means (40, 42, 43; 61, 42, 43) for adjusting the frequency of the energizing current, depending on the derived measure (P, .phi.), to a value for which said measure indicates that the power consumption of the motor (3) is maximal.

Abstract: An electro-optical apparatus comprising an objective (7) scans an optical disc (3) having a transparent protective layer (5) by means of a radiation beam (10) which, through the transparent layer, is focussed on a reflecting recording surface (4). The objective moves along the optical axis (19) for focussing the radiation beam on the recording layer and moreover performs limited pivotal movements. The position of the optical axis of the objective is corrected for obliquity of the surface of the optical disc, correction means (22A, B) being provided to tilt the objective through a correction angle, so that the angle between the optical axis and the normal to the disc surface is reduced.

Abstract: A sub-assembly (20) of a housing for electronic equipment and which is capable of carrying electronic components. The sub-assembly (20) comprises an injection moulded plastics body having an area (21) in which a regular array of apertures (22) are formed, pushbuttons (23) being mounted in each aperture of the regular array of apertures. The pushbuttons (23) are shaped and dimensioned so that they cover the whole of the first area (21), the gaps between the pushbuttons (23) being limited to those required to allow clearance for operation of individual pushbuttons (23). Some of the pushbuttons are replaced by cover plates (24,25) which are mounted in appropriate apertures of the array of apertures.The pushbuttons (23) operate on dome shape elastomeric switching elements (45) arranged between the pushbutton plungers (43) and the printed circuit board (40). The domes have an electrically conductive portion which bridges conductive tracks on the printed circuit board when the corresponding pushbutton is depressed.

Abstract: A nonlinear control system adapted to drive and control the speed, stroke, phase and center position of a reciprocating linear motor by means of phase locked loop techniques and the electromechanical filtering properties of linear motors. The control system comprises a tri-state switching amplifier in conjunction with 3 distinct feedback control loops to accurately determine the amplitude, center position and phase of the motor. The first feedback control loop includes a low pass averaging circuit and compares the motor position with a reference signal to achieve the desired motor position. The second feedback control loop includes a peak detector and determines the stroke of the reciprocating motor. The third feedback control loop operates as a phase locked loop to control the phase of the motor. The control system provides high efficiency, high reliability and low cost.

Abstract: A magneto-optical light switching element comprising islands which are formed from an epitaxial layer on the basis of bismuth-substituted rare earth metal iron garnet, which layer is provided on a magnetically unordered, optically transparent, (111)-oriented garnet substrate, integrated heating resistors being provided on the islands which are surrounded by a coil, the epitaxial layer being grown from a melt which contains lead oxide and boron oxide as a flux, the boron content of the melt used for growing the epitaxial layer being in the range from 12.7 to 25 at % (cation content) and the coil being constructed as an integrated coil.

Abstract: In a magnetic resonance imaging apparatus having a comparatively large measurement region, such as used for medical diagnosis, high-order contributions to the magnetic field are compensated for by the addition of pairs of rings made of a soft-magnetic material, so that the homogeneity of the magnetic field is locally increased to a high degree. This makes possible to use a substantially shorter coil while the field homogeneity in the measurement zone is still improved.

Abstract: A speed control system for an a.c. electric motor (1) comprises a microcomputer (6) having an interrupt signal input (INT/TO) to which is coupled the outputs of a detector (10) for detecting zero-crossings of the a.c. supply voltage and a tachogenerator (11) driven by the motor. The microcomputer supplies firing pulses to a triac (2), connected in series with the motor, in response to an overflow of a clocked counter (CT). This counter is suitably preloaded at each zero-crossing. The counter is read each time a tachogenerator pulse occurs and the time which this reading indicates has elapsed since the immediately preceding zero-crossing is stored. A record is also kept in a register (ZCSLTA) of how many zero-crossings occur between each tachogenerator pulse and the next and from this, and the stored times relating to the relevant pulses, the period of the tachogenerator pulses and hence the actual speed of the motor is calculated.

Abstract: A supply circuit for supplying a smoothed direct current to a load comprises a series FET element in series with the load resistance. The supply circuit is fed from the AC supply network via a rectifier 54 and a smoothing capacitor 52 causing a ripple voltage to be present on the input terminals 2-1 and 2-2. The direct voltage component of the input voltage is present across load resistance 60 and the alternating voltage component of the input voltage is present across transistor 10. In the case of known supply voltage circuits the voltage drop across the series element is selected to be equal to the maximum peak-to-peak value of the alternating voltage component thereby causing unnecessary power dissipation to be developed at a minor ripple amplitude. This will cause rapid ageing of the series element. The supply circuit in accordance with the invention comprises a comparator 42 comparing the voltage across FET transistor 10 to a threshold voltage.

Abstract: An optical scanning device is described which comprises a radiation source (6), an objective system (8) and a diffraction grating (9) which is arranged between the objective system and the radiation source to separate the radiation beam (b') reflected by the information surface (2) to be scanned from the beam (b) emitted by the radiation source and for introducing astigmatism in the reflected beam (b') for the purpose of focus-error detection. In principle, the grating (9) has a constant grating period and is arranged at a small angle (.alpha.) in the beam (b').

Abstract: A method and apparatus for providing dialling intervals in dialling sequences indirectly dialled by a register in which such sequences are stored, such intervals being in accordance with the dialling intervals produced by a user during direct dialling of such sequences. Direct dialled subscriber numbers which include a dialling interval after at least one digit therein, such as for line access, are stored in a reference memory along with such interval. Upon an indirect dialling of such sequence from a redial or abbreviated dialling register, a microprocessor in the telephone set compares such sequence digit by digit with sequences stored in the reference memory, and if there is a match inserts in the dialled sequence the dialling interval in the matching stored sequence.

Abstract: A high-frequency differential-amplifier stage. The collectors of the transistors (T.sub.1, T.sub.2) are connected to the emitters of two transistors (T.sub.3, T.sub.4) coupled to provide feedback between their collectors and their bases and which are biased by means of resistors (R.sub.1, R.sub.2). This input stage forms a resonant circuit. Two current sources (R.sub.32, T.sub.32, R.sub.31, T.sub.31) improve the operation of this stage in the saturated mode.

Abstract: An isocentric examination stand for radio-logical examinations of a patient comprising a cradle in the form of an arc of a circle which is circularly displaceable, a cradle support, an X-ray source and a radiation detector, the cradle being composed of mechanically assembled elements forming a structure defining the geometry of the cradle. The structure permits the passage of a supply cable of the source and of the detector into the cradle support.

Abstract: Broadband digital signals in a broadband communication network asynchronously operated space-division-multplex switching networks are arranged in the nodes. This asynchronous operating mode of the space-division-multiplex switching networks requires, in constructing the broadband communication network, the use of asynchronous multiplexers with complicated stuffing methods. For the implementation of a synchronous broadband communication network, the regenerated broadband digital signal is applied to an elastic store, entering the data into the elastic store being effected with the regenerated clock and reading with the central network clock. In the absence of a broadband digital signal because of a "not switched-through" switching state or a failing digital line, a switch to a broadband, network synchronous signal or to a substitution path is effected.

Abstract: An information transmission system is provided for a guided missile 1 in which guidance information is transmitted from the missile launch point to the missile along a beam 8 of 10 .mu.m wavelength radiation. The missile has a rearwards facing optical system 9 to collect and focus the radiation onto a cooled cadmium mercury telluride detector. The proportion of cadmium to mercury in the detector is chosen so that just after launch in the early stage of detector cool-down the long wavelength cut-off of the detector just includes the 10 .mu.m radiation, providing an early guidance signal, and so that, as cooling proceeds, the long wavelength cut-off moves to longer wavelengths thereby rapidly enhancing the received signal to compensate for loss of received energy at the missile due to missile range increase.

Abstract: A pulse-drive circuit for an electric motor in which the steep edges in the drive-signal are made to vary substantially stepwise, i.e. around a first time instant the signal changes from a first level to a second level and around a second instant the signal changes to a third level. This makes it possible to reduce a mechanical resonance vibration having a period of twice the time interval between the two instants.

Abstract: A power supply circuit which maintains the voltage across a first capacitor (C.sub.1) substantially constant over a wide range of mains voltages, the capacitor (C.sub.1) energizes a motor (M) and is charged during the rising edges of the applied mains voltage in that above a specific input voltage (U.sub.min) a first transistor (T.sub.1) is turned on via a second capacitor (C.sub.2) and a first resistor (R.sub.2). When the rectified mains voltage at the output of a diode (D.sub.1) exceeds a specific value (U.sub.2) defined by a first zener diode (Z.sub.2), a second transistor (T.sub.2) is turned on. Consequently, the first transistor is turned off. When the first transistor (T.sub.1) is cut off, the first capacitor is discharged through the motor. The second capacitor is then discharged via a second zener diode (Z.sub.1) and prevents the first transistor from being turned on.

Abstract: In DAV (data above voice)-systems an analog speech signal is transmitted in the low-frequency portion of the spectrum of an encoded data signal. When a data signal encoded by the known WAL2 code is used, the high-pass filters, required for the separation of the two signals produce intersymbol interference extending over a large number of bit intervals, requiring complicated equalisers at the receive end for good detection. When encoding the data signal in accordance with the DAV-code, as illustrated in FIG. 2 this drawback is remedied. In addition, this DAV-code is advantageous in that the amplitude fractions, represented by a and b, can basically be chosen at will, allowing the low-frequency content of the code to be affected. When (a; b)=(11/16; 3/16) the encoded data signal can be generated very accurately and in a simple manner.

Abstract: The invention relates to an apparatus for playing back and/or recording information on rotary optical discs comprising a device for clamping the optical disc in position on a disc aligner mounted on a rotating spindle. The clamping device comprises a disc loader which moves with clearance in a support which is movable between a rest position and an operating position. The disc loader exerts a clamping force on the disc during operation due to a magnetic force between magnets secured to the disc loader and the support. Rattling and an oblique position of the disc loader are precluded in that the magnets are arranged to exert a magnetic force which acts between the support and the disc loader so as to clamp the disc loader against the support when the latter is not in its operating position.

Abstract: A signal channel system which is particularly suitable for the employment of direct conversion receivers has a block of adjacent transmission frequency bands allocated to it. Each signal channel is split into two sub-channels or parts occupying mutually different frequency bands for transmission and the bands occupied by the sub-channels of the various channels are interleaved. In the receiver the local oscillator is tuned midway between the bands corresponding to the sub-channels of the wanted channel and the corresponding signals are recovered by bandpass filtering, phase-shifting, summing and differencing, demodulating and combining the frequency down-converted outputs of quadrature related mixers to which the received and the local oscillator signals are applied. Although d.c.