Abstract: An apparatus for reading permanently structured magnetic records having a first coercivity, comprising an oscillator having an inductive read head that is coupled to a circuit arrangement. At least one side of the read head sees an impedance that is larger than the impedance of the read head over the range of frequencies of interest, such that the read head provides an electrical signal in response to magnetic records having a second coercivity that is higher than the first coercivity (typically 2,000 to 5,000 oersteds). The electrical signal is derived from the voltage across the read head, which is preferably detected by a differential integrator that subtracts the voltages on either side of the read head to give a voltage difference, and integrates this difference over time.

Abstract: A record carrier has a secure first data storage device storing a plurality of different identification numbers in a sequence and a further data storage device storing a further number. The identification numbers are successive integers, and the further number is the least significant digit of one of the successive integers. The secure data storage device preferably includes permanently structured magnetic tape. The further number is derivable in a predetermined way from only one of the identification numbers, thus identifying uniquely which one of the identification numbers is characteristic of the record carrier.

Abstract: An optical device comprises a dispersion element, a reflector, and an angle-to-offset (ATO) element. The angle-to-offset (ATO) element has optical power. The dispersion element is positioned in or near a focal plane of the ATO element and adapted to separate an input wavelength division multiplexed (WDM) light beam received from an input port of the optical device into two or more channel light beams. The reflector is positioned in or near a focal plane of the ATO element and arranged to receive the channel light beams from the dispersion element via the ATO element. The reflector is designed to reflect at least one of the channel light beams toward a respective output port of the optical device. With this arrangement, the dispersion element, reflector and ATO element cooperate to optically demultiplex the input WDM light beam.

Abstract: A high capacity cross-connect in which a 3D switch core includes express paths that facilitate cascading of cross-connect blocks. A light beam propagates from an input waveguide 18 to a first MEMS mirror, which deflects the light beam to either an express optical path or a switching optical path. In the express optical path, the light beam propagates from the first MEMS mirror to a predetermined output waveguide, which is determined by the design of the switch core. In the switching optical path, the light beam propagates from the first MEMS mirror to a second MEMS mirror, which deflects the light beam to a selected one of a set of two or more output waveguides associated with the second MEMS mirror.

Abstract: Apparatus for coupling power into a body of gas by induction to provide a gas discharge, comprises a source of a/c power (3) coupled to a circuit arrangement having an inductor comprising two coils (1, 2), each constituted by a respective elongate conductor, the conductors each having one end coupled to the circuit arrangement at opposite respective sides of the inductor, and having the other end at a floating potential. The mutual capacitance between the coils, together with the inductance of the inductor as a whole, constitute a balanced self-resonant circuit having a resonant frequency which is greater than 1 MHz and less than 100 MHz. This arrangement can reduce temperature variations in the resonant frequency and can reduce unwanted r.f. emissions.

Abstract: The title of the invention is Cable Management Device. An apparatus and method for managing cables in a communication rack system having a first upright support member, a second support member spaced apart from the first support member to define an upright plane, a plurality of fastening locations along the first and second support members, an electronic device releasably mounted to the support members at selected fastening locations, and a plurality of cables projecting from a front surface of the electronic device. In one embodiment, a cable management device includes a mounting structure and a support structure. The mounting structure generally has a plurality of universal mounting sites arranged to correspond to the fastening locations along a portion of the first and second support members so that the mounting structure can be releasably affixed to the support members at selected fastening sites.

Abstract: Combinations of optically coupled Generalized Mach-Zehnder Interferometers (GMZIs) result in switches of greater switching capacity than an isolated GMZI. In a preferred form, the present invention provides a balanced non-blocking switch by using symmetrical configurations of optically coupled GMZIs, and also provides a cascaded non-blocking switch by cascading an N×N GMZI with a (N−1)×(N−1) non-blocking switch.

Abstract: An electrochemical cell sensing circuit for an electrochemical cell having a working electrode, a counter electrode and a reference electrode in an electrolyte, which in use, when a gas to be analysed is introduced into the cell, generating a current between the counter electrode and the working electrode, and a potential at a position in the electrolyte is sensed by the reference electrode.

Abstract: Glow discharge apparatus comprises a light-transmissive body (101) defining a cavity (102) containing neon or xenon gas. The glow discharge is powered by one or more electrodes (103) external to the cavity. The apparatus also comprises a secondary light source (104) for illuminating the neon gas to provide electrons in the cavity, thereby assisting discharge initiation in intermittent use, for example when controlled by a pulse time modulation drive circuit (107).

Abstract: An optical apparatus is disclosed that includes a first Z×T optical switch having Z input ports and T output ports, where T is at least 2, optically coupled to an integrated optical generalized Mach-Zehnder interferometer. The result is an optical switch, which is operated using a smaller number of control elements and control levels than the generalized Mach-Zehnder interferometer alone.

Abstract: A method of identifying a data carrier such as a credit card, benefit card, access control card, identity card or stored value card, carrying data in the form of a plurality of rational number in a sequence, successive numbers having a marker between them, comprises a) measuring the distance from a fixed point on the data carrier to a given part of a marker, b) dividing this distance by the distance between corresponding give parts of successive markers, thereby obtaining a rational number, and c) subtracting this rational number from the number in the sequence adjacent the marker in a given direction, thereby obtaining a further rational number which is capable of identifying the data carrier uniquely.

Abstract: In order to overcome problems with residual d.c. offset, and input signals with arbitrary timing, a drive circuit for a ferroelectric liquid crystal device includes a counter arranged for counting between first and second predetermined values in response to an input signal. The counter is designed so as to count in a first direction in response to a positive edge of the input signal and in a second direction in response to a negative edge of the input signal. Gating and latching circuits are responsive to the counting of the counter and the direction of count so as to provide appropriate positive or negative output voltage pulses for driving a ferroelectric liquid crystal device. An output stage comprising a bridge circuit is coupled via a step up transformer to the display device.

Abstract: An apparatus and method for managing cables in a communication rack system having a first upright support member, a second support member spaced apart from the first support member to define an upright plane, a plurality of fastening locations along the first and second support members, an electronic device releasably mounted to the support members at selected fastening locations, and a plurality of cables projecting from a front surface of the electronic device. In one embodiment, a cable management device includes a mounting structure and a support structure. The mounting structure generally has a plurality of universal mounting sites arranged to correspond to the fastening locations along a portion of the first and second support members so that the mounting structure can be releasably affixed to the support members at selected fastening sites.

Abstract: A drive circuit arrangement for a gas discharge lamp includes a) a self resonating inverting for providing a drive voltage across a load impedance, the inverter having a pair of field effect transistors which operate in anti-phase, b) a tank circuit for canceling the reactive component of the load impedance coupled to the inverter, c) a voltage division circuit which provides a given fraction of the drive voltage to the gates of the field effect transistors, and d) a phase shifting means comprising an inductance in series with the tank circuit for shifting the phase of the given fraction of the drive voltage. The voltage division circuit is provided with a voltage limiter which in operation provides a further phase shift to the given fraction of the drive voltage when the drive voltage exceeds a given threshold value, increasing the resonant frequency of the inverter and limiting the peak drive voltage.

Abstract: This invention relates to a composite image arrangement, comprising a pattern and a further pattern, substantially parallel to the first pattern, each comprising a plurality of visually contrasting regions, the patterns being in fixed positions relative one to the other on either side of a light transmissive lamina.

Abstract: The invention is directed to the use of wavelength channels to bypass nodes in ring networks. For networks with a small number of nodes, direct node to node routes are provided without changing the physical layout of the fibre in the ring. Architectures providing complete transparent interconnections with extra capacity for heavily used routes on a portion of the ring are disclosed. For networks with a large number of nodes, underconnected networks provide a number of accelerated, direct routes between some of the nodes. Proposed architectures for underconnected networks and methods for self-routing the traffic are also provided.

Abstract: An improved fiber optic delay line filter is disclosed having each fiber optic light path terminate on a corresponding photo detector adapted to convert the received optical signal to a commensurate electrical signal in bi-polar proportion to an electrical bias level provided to the photo detector where the bias level for each photo detector is independently settable and the outputs of all of the photodetectors are summed to produce an output electrical signal that is filtered by the arranged fiber optic delay line transversal filter.

Abstract: Logic circuits employ photoresponsive GaAs field effect transistors to directly drive GaAs laser diodes to provide optical output signals in response to optical input signals. Since the only electrical inputs are DC bias voltages, each such circuit can be readily decoupled, such as for use in electrically noisy environments. The optical output represents a predetermined logic condition in response to a predetermined operating current applied to the laser diode as a result of the operation of the photoresponsive device. Two photoresponsive devices may be used to apply two different operating current magnitudes to the laser diode to produce two different optical output signals.