Abstract: A frequency shift keying system for transmitting a signal which is a function of supplied data, includes first and second frequency generators producing first and second frequencies which differ in value by an amount which is a function of the maximum baud rate of the data. A counter is responsive alternately to one and the other of the two frequencies supplied thereto as a function of the data values for alternately counting up and down between values which differ by some given amount. The counter output in analog form is the transmitted signal. This system is particularly adapted to minimum frequency shift keying.

Abstract: A photon energy activated PIN diode is reverse biased by a continuously supplied direct current voltage. The PIN diode is rendered conductive for passage of a radio frequency input signal when it is illuminated. Continuous illumination of the PIN diode is not required for conduction such that illumination may be pulsed on and off while the diode remains conductive.

Abstract: A circuit which converts one parameter to another such as from temperature to electricity. The circuit comprises a three winding differential transformer with one winding connected to output terminals and each end of the other windings connected to a source (or drain) of a different one of four field effect transistors. The circuit is adapted for receiving an alternating current source to be coupled between drains (or sources) of the transistors connected to one end of each winding and the drains (or sources) of the other transistors. A temperature measuring device and reference temperature measuring device are connected to respective ones of two of the transistors to set the current limits of the transistors as a function of temperature. A voltage produced at the output terminals, when the alternating current source is applied, is proportional to the difference in temperature of the temperature measuring devices.

Abstract: An improved composite material which overcomes the moisture problem associated with other composite materials includes a protective waterproof coating of material such as a poly-para-xylylene over the composite material.

Abstract: In a burst mode fiber-optic transmitter-receiver or bus interface unit (BIU), the clock recovery process by a phase lock loop (PLL), or more generally a servo loop, detects the frequency difference between the PLL oscillator and the transmitter oscillator, and generates a control voltage which is combined with the voltage controlled oscillator (VCO) error voltage to urge the PLL oscillator towards the transmitter's frequency. An activity detector detects the presence of received signal, and "freezes" or holds the control voltage to the PLL so the PLL is free to slew to the frequency and phase of the clock of the received burst. Thus, the PLL is maintained near the expected frequency of the received clock signal for fast acquisition. After the burst, the activity detector once again allows the frequency control signal to assert command of the VCO frequency.

Abstract: The invention relates to a connective apparatus between a truss beam and another object, e.g., a second truss beam or another device, for rigidly joining the two together. The connective apparatus comprises a unitary attachment device which is connected to one of the frame elements in a truss beam. The device includes a rabbet member capable of attachment to a pair of struts of the frame element and a connector member attached to the rabbet member. A connector strut is provided for joining two or more truss beams to each other by interconnecting two nodes of the respective beams.

Abstract: A solder stop composition and a method of preventing a melt condition in a meltable metal alloy on a substrate, such as a circuit board, wherein the composition applied on the alloy contains a water soluble binder, a viscosity control agent, a thermal insulator filler, a water soluble moisturizer extender control agent and water. The dried composition is non-tacky and can be removed from the substrate with water. A typical composition capable of being cured to a dry state on a substrate contains water, glycerin, amorphous silica, glass microballoons filled with inert gas and ethylene glycol.

Abstract: A transmitter has an interleaver that sets an interleaving interval in accordance with the fading characteristic of a channel and transmits in another channel. The inteleaver duration is indicated by a synchronization signal and typically is 3 to 10 times the mean time between fades (decorrelation time). If the two channels substantially differ in frequency, a scaling factor can be used. A receiver has an adaptive deinterleaver that has a deinterleaving time in accordance with the synchronization signal occurring at the interleaving interval.

Abstract: A light-activated PIN diode switch arrangement is coupled to a source of direct voltage and to a load for control of the flow of load current. The PIN diode switch arrangement is connected so as to be electrically reverse-biased, so that no current flows therethrough. A source of light is coupled to the active portion of the PIN diode switch arrangement for rendering it conductive when flooded with light. High power and low inductance is provided by a configuration in which two PIN diode sets are physically and electrically connected together in a physical and electrical stack by a conductive heat sink. Laser diode arrays above and below the diodes of the stack selectively illuminate the intrinsic region of each diode bath through the adjacent doped region and also directly through the side of the diode.

Abstract: Heat conducting laminates and laminated heat conducting devices having at least one layer of metal and at least one layer of polymer matrix composite material having low-thermal-expansion reinforcing material distributed throughout and embedded therein. The coefficient of thermal expansion and the thermal conductivity of the laminated heat conducting devices are defined by the metal in combination with the polymer matrix material and the low-thermal-expansion reinforcing material in the laminate. The coefficient of thermal expansion and thermal conductivity of a heat conducting device can be controlled by bonding at least one layer of metal to at least one layer of polymer matrix composite material having low-thermal-expansion reinforcing material distributed throughout and embedded therein. In one embodiment, the laminated heat conducting device comprises a plurality of alternating layers of aluminum and epoxy resin having graphite fibers distributed throughout the epoxy resin.

Abstract: A truss structure for use in a gravity-free environment is disclosed together with methods and apparatus for constructing the same. The structure, characterized by high stiffness and a precise self-determined geometry and having a prism-form with square right cross section, is constructed from a plurality of substantially identical triangular frame elements. The truss structure may be manually constructed from a multi-row chain of interconnected elements or from a four row network of elements. The structure may also be constructed using an automatic method wherein individual frame elements are fed from four stack support and feed units to a holding fixture having a square cross section.

Abstract: An optical recorder such as a data recorder has an interchangeable, prealigned laser diode/lens module arrangement which can be readily replaced without complex realignment of the recorder. The module includes a cylindrical outer housing/heat-sink, and a tiltable yoke within the outer housing/heat-sink. A heat pump such as a thermoelectric element has a hot side coupled to the yoke, and also has a cold side. A combination mount is at least thermally cantilevered from the cold side of the thermoelectric element, and is thermally isolated from adjacent structures. A laser diode is bonded to a structure within the combination housing, and a lens is loosely mounted at the light-emitting end of the combination housing. The module is prealigned by operating for a period sufficient to achieve thermal stability in a fixture which is dimensionally identical to the optical recorder with which the module is to be used.

Abstract: The inability of the lens of an optical disc recorder to focus rapidly may be the salient factor limiting the data transducing rate. In order to provide smooth motion of the focus head and to maximize its speed, a focus lens assembly for an optical disc recorder is resiliently supported by one or more diaphragm springs, and is driven by a magnetic-coil arrangement to focus light onto the optical disc. Each diaphragm spring includes inner and outer support regions connected by a plurality of resilient support arms. Each support arm has straight, parallel sides and extends nonradially.

Abstract: An external-cavity laser includes low-level, broad spectrum light sources and plural light amplifiers. The external cavity includes a common partially reflecting mirror, and a common diffraction grating which couples the mirror to the light amplifiers. The feedback light is at a different wavelength for each amplifier, so that lasing takes place at plural wavelengths. The output light, while deriving from plural light amplifiers, occurs as a single light beam comprised of plural wavelengths.

Abstract: A secondary electrochemical cell includes a source of hydrogen as the hydrogen-providing reactant and an alkali or alkaline earth metal as the metal reactant. Hydrogen may be from H.sub.2 gas or a metal hydride. By separating the two reactants by a barrier selective for the passage of hydrogen ions, current flow may be induced in an external circuit connected across the barrier. The barrier is typically an electrolytic salt enclosed between a pair of solid metal electrodes. Electrons are gained by the hydrogen as it enters the electrolyte and lost by the hydrogen as it leaves the electrolyte. By connecting the metal electrodes, a circuit is established.

Abstract: An automatic direction finder antenna array having a plurality of pairs of oppositely positioned antenna elements arranged radially from a common center with each pair forming a cardioid radiation pattern when energized. Switching apparatus energizes successive antenna pairs to produce a rotating cardioid pattern but with the cardioid being switched back and forth 180.degree. at a higher switching frequency when each pair of antennas is energized during the rotating function. The antenna AX whose output bears the lowest ratio R to the output of its oppositely positioned antenna is determined as well as the antenna AZ having the largest output signal VZ. The precise angle of reception of a received signal is then determined from AX, AZ, and R.

Abstract: A truss structure for use in a gravity-free environment is disclosed together with methods and apparatus for constructing the same. The structure, characterized by high stiffness and a precise self-determined geometry and having a prism-form with square right cross section, is constructed from a plurality of substantially identical triangular frame elements. The truss structure may be manually constructed from a multi-row chain of interconnected elements or from a four row network of elements. The structure may also be constructed using an automatic method wherein individual frame elements are fed from four stack support and feed units to a holding fixture having a square cross section.

Abstract: A system for converting heat energy into electricity includes a conversion cell comprising a pair of spaced-apart electrodes having an electrolyte therebetween. The electrolyte is selected to pass negatively-charged hydrogen ions and to inhibit the passage of atomic hydrogen and positive hydrogen ions. Inducing a flow of hydrogen through the cell, a current may be generated between the electrodes as electrons are gained by the hydrogen as it enters the cell and lost by the hydrogen as it leaves the cell. In the preferred embodiment, hydrogen flow is induced by reacting the hydrogen leaving the cell with lithium or sodium to form the metal hydride. The metal hydride is then thermally decomposed to release the hydrogen and the molten metal to be recycled to the cell. In this way, the thermal energy used to decompose the metal hydride is converted into electrical energy by passing the hydrogen through the conversion cell.

Abstract: The effective capacitance of the floating diffusion in a floating-diffusion electrometer is modified to adjust electrometer sensitivity. This is done by changing the direct potential applied to a gate electrode proximate to the floating diffusion.

Abstract: A rotatable drum is arranged around a surface lying generally parallel to the axis of rotation, a plurality of bar code patterns, the individual bars making up each pattern extending normal to the rotational axis. A light beam in a plane is projected onto the surface, the plane lying generally parallel to the rotational axis such that light strikes the surface. A light beam also in a plane is reflected from the surface, the beam having relatively light and relatively dark regions corresponding to the particular bar code patterns upon which the projected beam is imaged. The reflected beam is passed through a cylindrical lens which fans the reflected beam into a wedge shaped beam projecting onto an object in the path of the beam successive bar patterns as the drum rotates.