Abstract: A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

Abstract: A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

Abstract: A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

Abstract: A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

Abstract: A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

Abstract: A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

Abstract: The probe for inspecting electrically conducting parts (1) of the invention comprises a row of transmitter and receiver coils (27), (28) that form an array of energized coils. The receiver coils (28) are influenced by different magnetic fields created by several neighboring transmitter coils (27) at the same time, making them sensitive to different types of flaws. The array of energized coils is displaced along the row. The probes are usually used for inspecting steam generator tubes of nuclear power plants.

Abstract: A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

Abstract: A phase lock loop (PLL) arrangement includes a voltage controlled ring oscillator (VCRO) including delay elements whose delay is controlled by a control voltage produced by the PLL. A phase error detector is provided which compares pulses of a PLL feedback frequency with pulses of a delayed reference signal, the delay being provided by further delay elements controlled by the same control voltage. The phase error detector produces an output signal which indicates when phase error exceeds a predetermined tolerance, and also indicates an absence of frequency lock.

Abstract: A device for checking bent tubes by means of a probe, such as a pneumatically propelled eddy-current probe. The device comprises a sealing-tight enclosure adapted to communicate with the tube to be checked via a connecting tube. The introduction pressure of the probe is produced by a pneumatic circuit. The probe comprises a checking head and a cable having floaters and is wound on a coil driven by a torque motor. The introduction speed of the probe is controlled by passing it over a drive pulley, to which it is permanently applied by a strap tensioned by a spring, the pulley being mounted on the shaft of a constant-speed motor. Application to the checking of the tubes of heat exchangers, condensers and steam generators, more particularly of nuclear reacters.

Abstract: The invention relates to a process and to devices for the inspection of the surface of a member by means of an eddy current probe. By scanning the member means of the transducer following a given path, the sampled values of the signal supplied by the transducer are recorded for clearly defined positions of the transducer. By restoring the signals, it is possible to simulate a displacement of the transducer along a different path and/or simulate the displacement of a larger size or different type of transducer. The process may be used in steam generators in nuclear reactors and to the examination of irradiated fuel rods in these reactors.

Abstract: A device for positioning a member, such as a guide tube, so as to face the perforations of a plate. The device comprises a remotely fitted attachment finger, using for this purpose e.g. a pole onto which is threaded the remainder of the device. A remotely controlled locking system makes it possible to fix the two parts, each incorporating at least one attachment member and which can be fixed in a perforation. These displacements of the device, following the fitting thereof, are also remotely controlled. The device can be applied, to the inspection of the tubes of a steam generator of a nuclear power station by means of an eddy current probe or sensor.

Abstract: Process and device for non-destructive testing or inspection by eddy currents with correction of the air gap effects. A differential measurement and an absolute measurement are performed and the result of the former is divided by that of the latter, which supplies a signal with respect to which the effects of the air gap separating the probe from the member to be inspected are corrected. Application to the inspection and testing of metal members.

Abstract: An apparatus for sending a sensor, such as an eddy current sensor, into a condenser, heat exchanger or steam generator tube. The apparatus first sends the sensor, which is attached to a cable, into the tube by means of a pressurized fluid which pushes the sensor along tube interior. At the extreme of the sensor's travel into the tube, a first ferrule attached to the rear of the cable blocks a first hydraulic passage in the apparatus. By virtue of slidable control pistons in the apparatus, this blocking cuts off the pushing pressure behind the sensor and then causes wheels to frictionally engage the cable to pull the sensor back to its starting position. At this time, another ferrule, carried near the sensor end of the cable, blocks a second hydraulic passage to thereby disengage the wheels from the cable. The cycle of (1) sensor pushed into the tube (2) sensor withdrawn from the tube, is now complete.

Abstract: A circuit for automatically correcting a signal given by a differential pick-up. Said circuit comprises as many corrective channels as there are frequencies in the signal. Each of said channels, comprises a band-pass filter centered to the frequency ascribed to the respective channel, an analyzer for the resistive (X) and reactive (Y) portions of the filtered voltage, two stages for the separate treatment of said two portions, each of said stages comprising a threshold comparator, a counter, a digital-analog converter, and a multiplier for multiplying by a reference-signal, either in phase (as regards portion X), or in phase-quadrature (as regards portion Y), with respect to the pick-up energization. An adder is adapted to reconstitute a corrective voltage to be substracted from the input signal.

Abstract: The eddy-current testing device operates by translational motion of a probe within the interior of tubes to be tested. The probe comprises in succession from front to rear in its direction of normal translational motion a front guiding member, a coil-carrying member and a rear guiding member connected together by an elastic means which tends to maintain these three members in aligned relation. At least the coil-carrying member has maximum transverse dimensions which are smaller than the internal diameter of the tube. An emitter-receiver coil of the probe is connected electrically to an external supply and scanning system by means of a cable which is secured mechanically to the rear guiding member.

Abstract: Measuring bridge for a device for inspecting or checking by eddy currents of the type comprising a first pair of adjacent branches each constituted by a resistor and a second pair of adjacent branches in parallel with the first pair, whereof at least one of the branches is constituted by a winding which is sensitive to the faults of the part to be inspected, characterized in that it comprises a supplementary resistor connected in parallel on the said winding.

Abstract: A pneumatic drive device for a probe, more particularly for an eddy current measuring probe has a tight flexible tube in which the probe is movably mounted with a cable connected to the probe. A cable pushing and pulling device is connected to one end of the flexible tube and a compressed fluid is introduced into the flexible tube for driving the probe towards and then into the tube to be checked. A tight connection for the other end of the flexible tube to the tube to be checked is provided including a cylinder-piston-restoring spring assembly engaging the drive device beneath a tube to be checked and then disengaging the drive device from the tube which has been checked.

Abstract: A process of and apparatus for non-destructive eddy current testing involves the suppression of displayed lobes corresponding to fault parameters to be eliminated from the display. Elimination circuits are provided for operating on the measurement signal to remove the undesirable parameters from the signal by compensation of the effects produced by the parameters at different frequencies.