Abstract: In prior cellular radio transmission systems a base radio station (BS) periodically transmits references identifying control channels associated with such base radio station, references identifying control channels of adjoining base stations, and references identifying a substitute control channel. The invention reduces the number of references which must be transmitted by a base station, which is of particular advantage in an integrated services cellular radio transmission system. A transmission channel of each base station is assigned as a simplex message transmission channel (COCH) in which a given base station (BS) transmits to the mobile stations (MS) information describing the structure of the control channels (CCH). Such information includes references (NC) to message transmission channels of adjoining base stations and references (CC) to one or more control channels assigned to the given base station.

Abstract: A local area network including a controller connected to a transmission medium. A plurality of terminals are connected to the transmission medium to initiate a request for an address. Each of the terminals includes a means for locally generating and storing a random number. The random number is transmitted with an address request to the controller. The controller will assign an address to the requesting terminal and append to the assigned address the received random number. When the terminal receives the assigned address and determines that the appended random number is the same as that locally generated, the address is identified as the address of the requested terminal.

Abstract: An apparatus for writing and/or reading information in substantially concentric tracks on a disc-shaped record carrier. The tracks are scanned by a beam of radiation focussed into a light spot thereon, and detection means responsive to the light reflected from the tracks generates a radial error signal which varies substantially proportionally to the radial excursion of the light spot relative to a track over a control range of p/4, p being the track pitch. The detection means comprises an error signal correction circuit for deriving from such signal a control signal (S.sub.1) having a substantially proportional control range for excursions of the light spot up to a value exceeding p/2 from a track. The control signal is supplied to radial positioning means, and controls the radial position of the light spot on a track.

Abstract: A sequential buffer device for connection to a serially readable memory. The device has an input for serially receiving successive data frames, which frames contain user data, error detection data and error correction data in a predetermined pattern; a random access memory which is connected to the input in order to store the data of at least one frame received in a byte-wise first write operation, under the control of a byte-wise incrementable address counter; a cyclically operational error detection device which is connected to the input in order to execute an error detection on the basis of the error detection data in a frame received; an error correction device which is bidirectionally connected to the random access memory in order to localize and correct an error under the control of the error correction device and on the basis of the error correction data in the frame; and a first-in-first-out (FIFO) memory having a capacity which equals at the most the capacity of the random access memory.

Abstract: A switched mode DC power supply circuit for a telecommunication line, including a switched converter for charging an output capacitor from a DC source. The converter is controlled by a periodic control signal having a variable duty cycle so as to maintain a selected direct voltage level across the output capacitor. However, due to common mode currents on the telecommunications line, the capacitor may become charged above the selected voltage level even when the duty cycle of the control signal is reduced to zero. Such excess charge is returned to the DC source, without heat dissipation, by providing a further switched converter for coupling the capacitor to the DC source and which is controlled by a second periodic control voltage which is activated when the duty cycle of the first control voltage has been reduced to zero.

Abstract: A record carrier is described with an optically readable trackwise-arranged information structure, and an apparatus for reading said carrier. The distances between the tracks of the information structure vary so that by projecting, in addition to a read spot, at least one address spot to the information structure of a size such that is spans a number of tracks approximately equal the quotient of the average track distance and the amplitude of the track distance variation, the read spot can be rapidly addressed to a specific group of tracks. This is done with the aid of two detectors which are disposed in the path of the address-beam radiation which is diffracted in a first order by the information structure in a direction transverse to the track direction.

Abstract: In a mesh telecommunication network in which a hierarchic synchronization method is used for synchronizing the clock pulses of exchanges in such network, a class identification is assigned to the clock pulses of each echange corresponding to a hierarchical order of all the exchanges in the network. To maintain synchronization regardless of changes in the network configuration or failure of interconnecting lines, a synchronization identification is additionally assigned to each exchange. Each exchange transmits its class and synchronization identifications to the exchanges connected thereto, and all the identification received at any exchange are compared to determine the exchange connected thereto having the highest class identification and the highest synchronization identification in such class. The sychronizing clock pulses of such highest order exchange are then used for synchronization. Each exchange may also add to its identifications a mark to distinguish different operating conditions of the network.

Abstract: Apparatus for scanning a radiation-reflective information plane (2). A scanning beam of radiation (b) from a diode laser (4) is focused by an objective lens (6) on the information plane and the beam reflected therefrom is deflected by a composite diffraction grating (9) so as to form two asymmetrical radiation spots (V.sub.1, V.sub.2) respectively focused on respective pairs of photodiodes (18, 19; 20, 21). The relative outputs of the photodiodes in each pair control focusing of the scanning beam on the information plane. The photodiodes in each pair are separated by a strip (22',23') positioned so that it is at an acute angle to the line (22, 23) along which the asymmetrical reflected radiation spot formed on the relevant diode pair becomes displaced as a result of variations in the wavelength of the scanning beam. Such angle is set so the separating strip is on the line along which the center of the intensity distribution of such radiation spot becomes displaced as a result of such variations.

Abstract: A scanning device for an optical recording and/or reproducing apparatus comprises a mirror objective in the form of a transparent body one surface of which forms an internally reflecting concave reflector and the opposite surface of which forms an internally reflecting convex reflector. A beam of radiation from a radiation source enters a window in the concave reflector, is divergently reflected by the convex reflector back to the concave reflector, and is consequently reflected thereby through a second window in the transparent body so as to form a scanning spot focussed on an information plane to be scanned by the device. The mirror objective includes a phase grating by which radiation reflected from the information surface is separated from the scanning beam and is directed to a radiation-detection system.

Abstract: An apparatus for scanning the information plane of an optical record carrier with a radiation beam from a diode laser. The reflected radiation from the information plane is separated from the scanning beam and split into two sub-beams by a composite diffraction grating which also functions to focus the respective sub-beams on respective pairs of photodetectors. The composite grating consists of two sub-gratings which adjoin along a common bounding line, the sub-gratings having varying gratings periods and curved grating strips. Movement of the composite grating in the direction of the bounding line changes the axial imaging distance of the sub-beams from the grating, permitting adjustment of such distance to compensate for changes in the axial distance between the diode laser and the photodetector. The diode laser and photodetectors can therefore be assembled together as a single integrated unit.

Abstract: An apparatus is described for optically scanning an information surface by moving said surface relative to a beam, which apparatus comprises a radiation source for supplying a beam, a collimator lens and an objective for focusing the beam to a spot in the information plane. The height of the apparatus can be reduced and/or a beam having an asymmetrical cross-section can be converted into a beam having a symmetrical cross-section by arranging a reflective diffraction grating with a suitable grating period between the collimator lens and the objective, while the angle of incidence between the normal on the grating and the chief ray of the scanning beam deviates considerably from 45.degree..

Abstract: An in-line color picture tube including a deflection unit having a system of deflection coils accommodating two sets of soft magnetic correction elements. The first set is provided in the proximity of the center of the vertical deflection field and symmetrically with respect to the plane through the non-deflected electron beams. The second set is also provided in the proximity of the center of the vertical deflection field, but closer to the entrance side thereof and symmetrically with respect to the plane through the tube axis which is at right angles to the plane through the non-deflected electron beams. The second set of correction elements is thereby angularly rotated 90.degree. relative to the first set of correction elements. The first set provides conventional astigmatism correction, and the second set provides astigmatism correction of higher order components of the deflection field.

Abstract: A read apparatus for reading a record carrier (1) having a concentric track pattern comprises a scanning device (2, 3) for reading the information, and a separator circuit (4) for extracting a periodic synchronizing signal (Ps) from the information read. By means of a servo system, which inter alia includes a drive motor (9) for driving the disc 1 and a control circuit (5), the rotational speed of the disc is controlled so as to maintain the periodic synchronizing signal (Ps) in synchronism with a reference signal (Pr). The circuit (9a) rejects those signal components in the control signal (U) for the motor (9) which are caused by an eccentric position of the center of rotation of the disc relative to the track pattern. This prevents these signal components from causing an unnecessary dissipation of electric power in the motor, yielding a substantial improvement in motor efficiency.

Abstract: A slave-type interface circuit which can receive signals from a bus if the coding A.sub.0, A.sub.1 and A.sub.2 of its inputs S.sub.0, S.sub.1 and S.sub.2 corresponds to that mode of operation. The signals from the bus are then delivered to the inputs L.sub.1 and L.sub.2. With another mode of operation the coding of inputs S.sub.0, S.sub.1 and S.sub.2 corresponds to off-line operation on the basis of logic levels applied to the same inputs L.sub.1 and L.sub.2. A branching block (SBL) directs the signals from the inputs L.sub.1 and L.sub.2 either to a bus receiver RBUS or directly to a decoder CDEC controlling a group of switches (COM). In the case of operation with a bus, the bus receiver (RBUS) controls the logic for the progress for operations.

Abstract: An optical apparatus is described for scanning an optical record carrier comprising a radiation source supplying a scanning beam, a reflector for directing the scanning beam to the record carrier and an objective lens for focussing the beam to a scanning spot on the information surface . The mounting height of the apparatus is considerably reduced by integrating the objective lens and the reflector in a single reflector-objective element.

Abstract: A disk-shaped record carrier body for storing information which is recorded thereon by a beam of radiation. The carrier body comprises a follow-on track which is capable of being scanned with an opto-electronic system so as to produce an electrical signal for controlling the position of the beam during recording of the information.

Abstract: An apparatus for recording and/or reproducing information on an optically inscribable and readable disc-shaped record carrier with a previously formed track pattern containing a first track modulation, in order to obtain a clock signal, and a second track modulation formed by a radial wobble, in order to obtain a tracking signal. A reference signal for generating a tracking signal via synchronous detection is derived from the clock signal by frequency synthesis.

Abstract: An apparatus for recording and/or reproducing information in and/or from an optically inscribable and readable disk-shaped record carrier with a pre-formed tracks with a track modulation constituted by a radial wobble, in order to obtain a tracking signal. A reference signal for deriving the tracking signal by synchronous detection is obtained by rectifying the difference signal which is the difference between the signals supplied by the two photo-detectors disposed on opposite sides of a line which extends in the track direction, by subsequently extracting the component of twice the frequency via a phase-locked loop and by frequency-dividing the signal, so that phase shifts of 180.degree. in the difference signal do not affect the synchronous detection.

Abstract: Apparatus for scanning the information surface of an optical disc record carrier with a radiation beam. Errors in beam focus on such surface are detected by providing two optical gratings in succession in the path of the radiation reflected from the record carrier. The gratings have a constant grating period, which may be equal or in a fixed ratio, the directions of the grating strips of the two gratings intersecting each other at a relatively small angle, thereby forming a Moire interference pattern in the radiation emergent from the two gratings which rotates due to changes in beam focus. This changes the relative amounts of radiation received by an assembly of radiation detecting elements adjacent the second grating, producing a focus error control signal which can be employed for correcting beam focus.