Abstract: Data in the form of multi-value symbols is transmitted at a symbol rate 1/.DELTA.T. At the receiver a decision circuit supplies estimates of the transmitted symbols on the basis of the received symbols. The present invention concerns compensating phase noise after equalization, if any, of the received symbols and before application of the received symbols to the decision circuit (38, 39). The received symbols are in complex form with in-phase and quadrature components y.sub.k ' and y.sub.k " respectively. Phase noise is compensated by complex multiplication in a multiplier (36) of the received symbols by a complex coefficient m.sub.km.sub.k+1 =[m.sub.k -.lambda.(v.sub.k -a.sub.k)y.sub.k *]exp[-iF.sub.k (.epsilon..sub.j)]where:.lambda. is a real coefficient;y.sub.k * is the complex conjugate of the symbol received at instant k.DELTA.T+t.sub.o (where t.sub.o is the instant taken as the origin of time measurements);v.sub.k is the symbol applied to the decision circuit at said instant;a.sub.

Abstract: An automatic exchange with a digital switching network, for the connecton of circuits or subscriber lines, said exchange comprising at least one central computer, signalling receiver and sender peripherals serving said circuits or lines, switching network marker peripherals, all said peripherals being placed under the control of the central computer, and said circuits or lines being connected to the switching network by digital channels in time division multiplex links characterized in that certain peripherals (UPI, LMQ) are piloted by the computer through the switching network RCX, the messages enabling computer (UCA) to pilot at least one peripheral (UPI, LMQ) being carried by a digital connection comprising two TDM-PCM links (MIC-C, MIC-P/MIC-M) connected to the switching network, the first said link (MIC-C) connecting to the computer, and the second (MIC-P/MIC-M) connecting to said peripheral (UP1/LMQ).

Abstract: A remote surveillance and fault location unit for installation in each pulse generator repeater in a digital transmission link uses a service signal added to the digital data signal conveyed by the link. Each unit comprises a receiver circuit (100), a time base (200) and a transmitter circuit (300) suitable for implementation as an integrated circuit. The units add data representative of the performance of the repeater at which they are located to the service signal which is then monitored at one end of the link. The remote surveillance and fault location unit comprises a receiver circuit connected to an input to the pulse generator repeater for receiving a service signal if one is present at the input, a carrier frequency and clock bit frequency recovery circuits, a transmission circuit having its output connected to a second input of the pulse regenerator repeater for transmitting a service signal corresponding to the received frame to which data has been added.

Abstract: A screened box comprises a rigid surround defining four side walls of the box, three of which have edge portions folded towards the outside. Two screening panels are placed one on each side of the surround, each with an edge portion inserted in an inwardly directed recess on the fourth of the aforementioned side walls. The other three edge portions of the screening panels overlap the outwardly folded edge portions of the side walls of the box. Clamping bars are fitted over each folded over edge portion and the overlapping edge portion of the screening panel.The box is intended in particular for housing electronic circuits.

Abstract: A leak detector comprises helium measuring means (6) for measuring helium sucked in by a sniffer (2) via a flexible hose (3) and a liquid nitrogen trap (5). A vacuum is maintained in the nitrogen trap (5) by a molecular diffusion pump (7) leading to a vacuum pump (18) which exhausts to the atmosphere. In order to speed the flow of gas, possibly including helium as a tracer element, along the flexible hose (3) most of the gas sucked in by the sniffer (2) is diverted from the inlet (4) to the nitrogen trap by a bleeder arrangement (12) connected to an auxiliary duct (11) which is itself connected to an intermediate point between two stages in the vacuum pump (18).

Abstract: The invention relates to a method of regenerating the modulation carrier wave of an original modulated signal (SL) which has symmetrical frequency components about the carrier. A phase discriminator (D1) which receives two image signals (SL, S11) of the original signal controls the frequency of a local oscillator (OL), the frequency spectrum of one of the image signals being inverted with respect to that of the original signal and the difference in frequencies between these two image signals being twice that between the local carrier and the carrier of the original signal. Application to the synchronous demodulation of a television signal.

Abstract: A digital sinewave generator can be used in digital equipment, e.g. instead of a local oscillator for modulation/demodulation of signals. If there is no simple relationship between sampling rate and the frequency of the sinewave, successive sample values must be calculated since storage of these values would be prohibitive. For a sinewave Re.sup.jk.phi. sampled at successive instants k=0, 1, 2, . . . etc. separated by a phase angle .phi., quadrature components A.sub.k +jB.sub.k =Re.sup.jk.phi. can be calculated using the algorithm:A.sub.k+1 =cos.phi.A.sub.k -sin.phi.B.sub.kB.sub.k+1 =sin.phi.A.sub.k +cos.phi.B.sub.k.Unfortunately it is impossible for cos.sup.2 .phi.+sin.sup.2 .phi. to be exactly equal to unity if calculations are performed with finite precision using an even number base, which as the effect of causing the modulus of a sinewave generated by this algorithm to tend exponentially to 0 to .infin.. The present invention overcomes this by using the above algorithm to obtain approximations A.sub.

Abstract: The invention relates to apparatus for monitoring the operation of electronic equipment having a plurality of circuits to be monitored, each of which has a fault indication terminal (24). In accordance with the invention, fault simulation means comprise a cyclic address counter (9) having a higher number of states than there are circuits to be monitored, and which is arranged to switch the binary fault indicating terminal of a circuit to its fault condition when indicating the address of the circuit. When indicating an address that is not allocated to any of the circuits, none of the circuits ought to respond. A check is thus performed on the operation of the fault simulation means itself. The invention is applicable to electronic equipment requiring a high degree of security in operation, e.g. a redundant time base. The equipment may be analogue or digital.

Abstract: A switching network is disclosed having a time-division or space-division multiplex incoming stage and outgoing stage in which a terminal unit of the incoming stage and a terminal unit of the outgoing stage form a terminal module (ME1, ME2 . . . MEn) which can handle n multiplex links (LE1, . . . LEn). The terminal modules are formed into groups in which the traffic of a faulty module is distributed among the other terminal modules of the group and forwarded over an auxiliary incoming line (L9, L10, L11, L12) of each terminal module by an input switch (5, 6, 7, 8) associated with each terminal module. An output switch (9, 10, 11, 12) associated with each terminal module and linked to the auxiliary outgoing line (13, 14, 15, 16) of the other modules collects the distributed traffic.

Abstract: When a document is scanned, for example in a facsimile transmitter, an image analysis signal is formed. This signal has a level which varies between a maximum black level and a maximum white level and it is converted into an on/off (e.g. black and white) signal by comparison with a threshold. For good results on backgrounds of various tones it is necessary for the threshold to vary. The present pulse-forming circuit has a first detector 2 arranged over each scan line to detect and store a background level signal .DELTA.. It has a second detector 3 arranged over a few successive image points to detect an average value signal V'. These signals are combined by threshold determining circuit 4 to generate a threshold V.sub.d such that V.sub.d =K.DELTA.+K'.DELTA. where K and K' are two constants satisfying the relationships:0.ltoreq.K<1;0<K'<1; and0<K+K'<1, e.g. K=1/3 and K'=1/2A comparator 1 performs the on/off conversion of the analog analysis signal V.sub.a into a binary pulsed signal V.sub.

Abstract: Electronic equipment, e.g. a repeater and/or an equalizer is housed in an underwater housing (10). Each end of the housing is closed by a cover (11) and a sealed electrical connection must be provided between an underwater coaxial line cable (5) and the electronic equipment. The connection is provided by a lead-in length (1) of coaxial cable. This is initially connected to the electronics for final testing before it is sealed inside its housing. Thereafter the cover (11) and the sealing/fastening arrangements are threaded over the lead-in cable and the housing is sealed.

Abstract: A wide-band transistorized amplifier including between two line couplers a cascade of stages of amplification and a negative feed-back quadripole connecting the output from the last stage of the cascade to the input to the first, and including a stage of correction by forward gain control, which is arranged in parallel across one of the stages of the cascade, which is connected to one of the couplers, characterized by the fact that the stage (10, 12) of the cascade, across which the correction stage is arranged in parallel, introduces a phase reversal, and that the correction stage includes a CE transistor (20, 20', 20") the base of which is connected on the one hand through an inductive phase-shift impedance (19, 19', 19") to the input to the said stage (10, 12) of the cascade, and on the other hand through a resistor (23, 23', 23") to the output from the said stage of the cascade, and the collector of which is connected through the putting in parallel of a resistor (21, 21', 21") and a capacitor (22, 22', 2

Abstract: A connector comprises a base portion provided with contacts, a movable block and a device for displacing the movable blocks perpendicularly to the base portion, operation of the displacing device causing the movable block to take up a raised position in which it is possible to insert above the base portion a printed circuit board bearing contacts on one side facing the base portion, and a lowered position in which the printed circuit board is pressed against the said contacts provided on the base portion.

Abstract: The invention relates to an automatic gain control circuit for restoring an input signal whose variable level is to be regulated throughout the whole frequency band, in particular to restore the input signal to a constant level. A gain control loop uses n phase shifters (3,4) each phase shifting at the lower limit of the frequency band of the input signal by 2.pi./(n+1), being connected in cascade to the output of the circuit and followed by a rectifier and summing circuit (5) acting on the output signals of the circuit (S) and of each of the phase shifters (3 and 4) to generate a single polarity signal which, filtered by a cell (7) with a short time constant, constitutes the gain control signal. The circuit can be used in a modulator-demodulator to transmit data, in particular facsimile signals, over a telephone line.

Abstract: The present invention relates to the optical fibre technology and more particularly to fixed optical attenuators for insertion in an optical fibre transmission path. The optical attenuator includes an attenuator element 1, two lenses 2, 3 which are aligned with each other and separated by the attenuator element 1 and two optical fibre connections disposed on either side of the assembly formed by the lenses 2, 3 and the attenuator element 1. It may be used as a level adaptor between a source of light rays and a device which is connected to it by an optical fibre or in test, calibration or measuring instruments for optical fibre systems.

Abstract: The invention relates to a sealed connection between an optical fibre line cable (C) and an electronics-containing submerged housing (11) the connection being via an access provided in a cover (1) which closes the housing. The connection is constituted by a length of optical fibre cable called the lead-in cable (2), installed on the electronics block and including thereon a notched hollow tube (7) which surrounds the cable together with connection ring (10) which extends the notched part towards the inside of the housing; one end of which is fixed to the notched part (7), the other forming a stop for the cover, the connecting ring co-operating with means (19) for locking the cover against the stop, said connection including outer casings (16, 23, 22) which provide continuity of the seal between the lead-in cable and the housing of the repeater.

Abstract: A planar support member for an electric circuit, e.g. a printed circuit board, wherein at least a region of the support member includes magnetic material through at least a part of its thickness. A magnetic circuit is made in this material by forming at least one opening through it. The support member is then coated with insulative material and conductor paths are made on both faces of the support member by conventional techniques for such members. These paths include a winding disposed around a core part of the magnetic circuit with alternate half turns being formed on opposite faces and interconnected by through plating. The inductive circuit thus formed may constitute an inductor, a transformer or a relay.

Abstract: The present invention comes within the field of synchronous digital transmission. It relates to the recovering the carrier (which may be suppressed carrier) of an amplitude modulated synchronous digital signal. It provides a circuit which includes an oscillator (41) of adjustable frequency and phase to generate a local carrier, a demodulation circuit whose input(s) receives the local carrier (possibly phase shifted by .+-..PSI. (42,44,46,47) and the amplitude modulated synchronous digital signal e(t) and control means (48,49) which control the phase and the frequency of the oscillator from the signals delivered by the demodulation circuit and which comprise at least one sign coincidence autocorrelator. It advantageously applies to demodulating amplitude modulated single side band bipolar coded synchronous digital signals.

Abstract: In a facsimile system, for example, a document is scanned along successive scan lines and is analyzed by a photosensitive reader to produce an analog image analysis signal (V.sub.a). This signal is then converted into a two-value (i.e. black and white) signal by an all-or-nothing converter. This is done by a comparator (1) comparing the analog signal (V.sub.a) with a threshold (V.sub.d); and to avoid losing wanted information, in spite of varying background densities, it is necessary for the relative values of the analog signal (V.sub.a) and the threshold (V.sub.d) to vary so that the threshold remains somewhere between local maximum and minimum modulation levels over a range of absolute values.In the present invention successive modulation peaks are detected by a peak detector (2) and their values stored e.g. on a capacitor.

Abstract: The present invention comes within the field of synchronous digital transmission. It provides an automatic variable equalization network (1) equipped with phase-locking means, in which a sign coincidence autocorrelator (30) correlates the polarities of two versions of the equalized signal delayed in relation to each other by .tau., an integer multiple of the unit time interval of the transmission. It is used advantageously for equalizing synchronous digital transmission channels in switched telephone or telegraph networks.