Abstract: A system and method for weighing varying throughput of conveyed particulate material. The system has a weighing unit for measuring weight of material conveyed on a span of the conveyor and a speed monitoring unit to monitor the speed of the conveyor. A control module is programmed to calculate the instant value of material conveyed per unit length of the conveyor. An output from the control module reduces conveyor speed in response to a reduction in measured weight of material conveyed and increases conveyor speed in response to an increase in measured weight of material conveyed. High accuracy of measurement of the weight of particulate material being conveyed even when the conveyor is lightly loaded.

Abstract: A GaAs D-MESFET logic system having a low power delay product has a switching second and a voltage level shifting section. The voltage level shifting section consists of a chain of diodes and a pulldown transistor. The switching section consists of an array of D-MESFETs which acts to speed up operation of a coupling capacitor. The low power dissipation of known capacitor coupled D-MESFET logic is thus preserved, while reducing gate delay.

Abstract: A fiber optic star coupler particularly for use in providing optical interconnects between circuit boards has a light mixer into which input and output fibers are inserted. The mixer has rectangular cross-section passage, an interior surface of which is highly reflecting. The mixer is long enough to promote a degree of internal reflection of light from any one of the input fibers sufficient that the corresponding light intensity reaching the output fibers is substantially uniform. In an optical interconnect arrangement, interconnection between circuit boards in a rack or cabinet is achieved by mounting light emitting and light receiving units on each board and leading fibers to which the units are fixed to the fiber optic star coupler so that light from the emitter units enters one end of the light mixer and fibers leading to the receiver units enter the opposed end of the light mixer.

Abstract: A fiber optic access node has input and output fibers terminating at a housing. A module is retractably insertable into the housing to automatically lock into a position in which an output zone of the module aligns with the output fiber and input zone of the module aligns with the input fiber. The input and output zones may be those of fiber optic passive elements such as a bypass fiber, a fiber tap, a fiber extension loop or a wavelength division multiplexed device, or may be those of an active element such as a repeater incorporating a light emitter, a light detector and a control circuit. The fiber optic element may be encapsulated within a plastics block or can be clamped between two plates. The combination of module and housing allows rapid and easy substitution of fiber optic functions within a fiber network.

Abstract: The fundamental-mode field radius `w` is a key parameter in characterizing optical fibers. `w` is a function of P, .theta. and .lambda. where P is the far-field power passing through a circular aperture subtending a solid angle of 2.theta. at the fiber end face and .lambda. is the center wavelength of transmitted length. `w` is derived by moving a fixed diameter aperture along an axis extending between the test fiber end surface and a photodetector so as effectively to vary .theta.. At each location the power P incident on the photodetector and the corresponding acceptance angle .theta. are measured. A microprocesor is programmed to compute from the range of measured values of .theta. and P, the value of mode field radius for a particular transmission wavelength .lambda..

Abstract: Optical fiber proof testing equipment has a rotary drive and two pulleys directly coupled to the drive. A fiber is taken from fiber drawing equipment around part of the circumference of the first pulley, along a guide track and around part of the circumference of the second pulley. Respective continuous belts apply a resilient bias to clamp the fiber to the pulleys, the resilient bias being adjustable. The second pulley is marginally greater in diameter than the first pulley so as to establish a predetermined tensile stress in fiber moving between the two pulleys. The test equipment is used after fiber has been drawn in a drawing tower and then coated and before the fiber is stored on reels. The tensile force on the fiber can be changed by changing the diameter of the first or second pulleys. In addition some incremental change in the tensile force can be obtained by adjusting the resilient bias provided by the continuous belt.

Abstract: Particularly for use in multilevel metallization structures in which the underlying topography consists of fine and sharply contoured conductor lines produced by dry etching, conformal or near planar dielectric coatings are produced by depositing a dielectric layer to a thickness over the conductor of at least three times the conductor thickness. The dielectric is then anisotropically etched back to a thickness comparable with that of the underlying conductor. By this method a smooth dielectric top surface can be obtained without the requirement for multiple processing steps characterizing alternative planarizing techniques.

Abstract: A portable telephone hearing aid having an acousto-acoustic/magnetic amplifier providing a maximum gain of 20 dB has a circular housing at one end of a U-shaped resilient clip member for attaching it to the telephone receiver in a handset. A battery compartment, also housing an ON/OFF switch, and a gain control wheel, is located at the other end of the U-shaped clip.

Abstract: The eccentricity of an optical fiber core within a transparent fiber jacket is monitored by directing light towards the fiber and obtaining a returned light intensity profile as a function of the angle at which light is returned from the fiber. Any deviation from symmetry of the profile is an indication of eccentricity of the fiber core within the jacket. The method can be used for in-line monitoring when producing fiber with an extruded jacket. The technique is substantially simpler than known techniques which require the use of coherent light for generation of optical fringes.

Abstract: An integrated circuit device has a high resistivity silicon substrate in which a low resistivity region exists. A charge coupled array is fabricated in the high resistivity region and an output circuit is fabricated in the low resistivity region. At the boundary between the high and low resistivity regions a floating diffusion provides charge coupling between the array and the circuit. The low resistivity region is prepared in a high resistivity substrate at a temperature in excess of 1000.degree. C. to obtain a sufficiently deep low resistivity region but subsequent processing to produce the charge coupled array and the control circuit is performed at lower temperatures to minimize thermal degradation and contamination of the high resistivity region.

Abstract: To uniformly coat a fiber, it is fed downwards through a passage filled with a coating fluid. The passage has a downwardly tapering lower zone into which fluid is directed from outside the passage uniformly, radially inwardly and downwardly. The fluid directed into the lower zone suppresses turbulence within the fluid at a bottom outlet aperture within the lower zone. The passage at an upper zone is large enough to allow bubbles to float to the surface of the fluid. The arrangement prevents turbulence and air bubbles from causing thinly coated fiber regions which might adversely affect the fiber integrity. The passage is defined by two relatively moveable bodies so that the rate at which the coating fluid is injected into the lower zone can be varied.

Abstract: An improved melt dispensing liquid phase epitaxy (LPE) boat is disclosed. It comprises two separable compartments. A supply-melt reservoir and a growth-melt bin separable by means of a separation slider for separating the two compartments prior to the actual process of epitaxial growth. In a further improvement, the substrate holder has a melt collection bin for receiving used growth-melt.

Abstract: The screen of a display terminal has touch strips extending adjacent horizontal and vertical edges. The touch strips have electrical outputs dependent on the position along the strips at which they are touched. Using microprocessor control the touch strips can be made to manipulate a displayed image and control the rate or level or other terminal functions. By selecting an appropriate programming mode the touch strips can be made to present a series of programmable or soft keys. Also the touch strips can be used to provide a menu selection, scrolling and cursor generation and movement for word processing. The use of two touch strips requires less complex circuitry than a known transparent input overlay for the display screen. Moreover, it is a cleaner technique resulting in reduced image attenuation and distortion.

Abstract: An integrated circuit is fabricated with some redundant capacity by forming potential electrically conducting links which can subsequently be made electrically when extra circuit capacity is required. Field oxide is grown on a silicon substrate and then a layer of polysilicon deposited over the oxide. At the redundancy sites where electrical connections may subsequently be made, an anti-reflective silicon nitride coating is deposited and photodefined. The areas of this coating are used as masks in order to diffuse dopant into the polysilicon at parts of the polysilicon laterally adjacent the redundancy sites. When later it is necessary to bring spare capacity into the circuit the complete circuit is scanned with a continuous wave laser. The laser melts the polysilicon under the nitride mask permitting the dopant to diffuse from the adjacent parts of the polysilicon and so form a conducting link.

Abstract: The chromatic dispersion of an optical fiber such as a 10 to 50 km length of single mode fiber is measured by launching into the fiber the outputs of at least three commonly modulated semiconductor lasers having output wavelengths close to a region of minimum chromatic dispersion of the fiber. At a remote end of the fiber the relative phases of the signals from the three lasers are determined and a chromatic dispersion profile of the fiber is derived from the measured relative phases and the output wavelenghts of the lasers by assuming a parabolic relationship between signal propagation times and wavelength. The profile can be determined by defferentiating a parabolic function fitted to the three date points derived using said three lasers or by directly generating a linear relationship between chromatic dispersion and wavelength on the basis of two values of chromatic dispersion derived from these three data points.

Abstract: A surface acoustic wave (SAW) device has an input interdigitated transducer (IDT) and an output IDT. One of the transducers is formed as two loops which are interconnected so that unwanted magnetic feedthrough voltages induced in or by such current loops cancel, while currents producing or produced by the SAW add.

Abstract: In a mounting arrangement of lamellar, input/output devices for a computer or telecommunications terminal, one of the devices is movable relative to another of the devices between a limited operational position in which a first input/output device is operably exposed but masks a second device, and a fully operational position in which both the first and second devices are operably exposed. One embodiment has one input/output device sliding relative to a vertically adjacent input/output device. In another embodiment, input/output devices are hinged relative to each other and to a common cabinet base. The mounting arrangements offer the advantages of spatial economy, input/output device protection, and the capacity for an aesthetically attractive cabinet.

Abstract: Double heterostructure lasers which use a narrow stripe contact exhibit linear characteristics with a low lasing threshold current making them very suitable for fiber optic communication systems. Linearity and low threshold currents are achieved if the carrier current injected into the device is confined to a narrow region of the active layer. To further confine the current a p-type diffusion is performed to produce a relatively low conductivity path between the contact stripe and the lasing region of the active layer. Ideally the diffusion front extends to within 0.5 microns of the active layer. In order to achieve this, a p-type double heterostructure second confining layer of 0.5 microns or less is grown immediately adjacent to the active layer and an n-type blocking layer is grown on the second confining layer. By diffusing the p-type dopant through the n-type blocking layer the diffusion front can be accurately monitored using a scanning electron microscope.