Abstract: Improved digital encoding of an input speech signal for transmission uses an adaptive low-pass filter and adaptive coder responsive to the total spectral energy of the input signal, thereby providing reduced coder bit rate at constant coder noise, or conversely reduced coder noise at constant bit rate.

Abstract: Optical fiber switch apparatus for selectively coupling the end (16) of a first fiber (17) to the ends of a plurality of second fibers (10) circularly arranged within a housing (12) also enclosing the free end (16) of the first fiber (17). The latter (17) extends through a spherical bearing (20) seatable in a socket (24) formed in the housing end (23), the bearing having a disc (19) fitted about it at right angles to the axis of the first fiber (17). The pole-pieces of a plurality of electromagnets (26) arranged under the periphery of the disc (19) selectively tilt the disc (19) upon selective energization to swing the free end (16) of the first fiber (17) into juxtaposition with the end of a selected second fiber (10'). A hold electromagnet (36) is energized to urge the bearing (20) into its socket (24) and thereby the ends of the two fibers (17, 10') into abutment.

Abstract: A waveform generator (FIG. 1) contains a static energy storage device circuit in which storage devices (C1 through C6) are interconnected in a fixed topological configuration. The storage device circuit has a plurality of input and output terminals (12 through 18). Charge storage is accomplished by controllably steering (20, 40) a supplied DC signal (10a,b) to a selected one, or selected ones, of the storage devices via the appropriate input terminals. AC waveforms are generated (11a,b) by controllably selecting (30, 40), in predetermined sequence, each output terminal of the storage device circuit.

Abstract: A Differential Phase Shift Keyed (DPSK) receiver is arranged to detect DPSK signals that contain the O.degree. vector as an information bearing signal in its constellation. The received signal is phase shifted by 90.degree.. A 45.degree. phase shifted signal is thereafter synthesized by additively combining the DPSK signal and the 90.degree. phase shifted signal. Using these signals, detection proceeds by means of correlation techniques. The polarities of the correlation products uniquely determine the phase changes of the DPSK signal.

Abstract: An electrical terminal pin (10) adapted for engagement with a plated-through hole in a printed wiring board backplane. The pin includes at least one end (12) for receiving electrically conductive elements and an S-shaped compliant portion (16) adapted and dimensioned to minimize deformation of the plated-through hole. The compliant portion (16) includes a transition section (17) in which the S-shaped cross section evolves from the square cross section of the end (12) of the pin (10). Because of the varying dimensions in the transition section (17), a smaller plated-through hole, which requires more "conditioning" than a larger hole, will be first encountered by a relatively stiffer part of the pin (10). As a result, the tolerance required in the production of plated-through holes may be increased.

Abstract: An optical receiver having enhanced dynamic range is achieved through the use of a variable impedance shunt 203 disposed at the receiver input. The optical receiver comprises an optical detector 102 serially connected to a transimpedance amplifier 201. The optical detector 102 receives an optical signal having a variable optical power level and modulation bandwidth and generates a corresponding electrical current therefrom. The transimpedance amplifier provides a fixed amount of gain and converts the electrical current to an output voltage. An automatic gain control circuit 202 produces a control signal which varies in response to the amplitude of the output voltage. The control signal is applied to the variable impedance device to vary the impedance therein. This maintains the output voltage at a predetermined amplitude over the modulation bandwidth without any significant reduction in receiver sensitivity.

Abstract: The present invention relates to a low power, beam switchable, antenna comprising a focusing reflector (14), a plurality of feedhorns (10.sub.1 -10.sub.N) disposed on a surface (.SIGMA.) adjacent the focal surface of the focusing reflector, and an amplifying array (20, 24, 28) disposed in the aperture of the focusing reflector. A spherical wavefront launched by a feedhorn is reflected by the focusing reflector into a first planar wavefront which is intercepted by the amplifying array using a planar array of first feed elements (20.sub.1 -20.sub.X) disposed on a fourier transform surface (.SIGMA.') of the surface on which the feedhorns are disposed. The signal produced by each of the first feed elements associated with a first planar wavefront is separately amplified with an equal relative phase shift to the other associated intercepted signals and reradiated in a second planar wavefront by a planar array of second feed elements (28.sub.1 -28.sub.

Abstract: Magnetically actuated devices such as, e.g., switches and synchronizers typically comprise a magnetically semihard component having a square B-H hysteresis loop and high remanent induction. Among alloys having such properties are Co-Fe-V, Co-Fe-Nb, and Co-Fe-Ni-Al-Ti alloys which, however, contain undesirably large amounts of cobalt.According to the invention, devices are equipped with a magnetically semihard, high-remanence Fe-Mo-Ni alloy which comprises Mo in a preferred amount in the range of 2-26 weight percent and Ni in a preferred amount in the range of 0.5-15 weight percent.Magnets made from alloys of the invention may be shaped, e.g., by cold drawing, rolling, bending, or flattening and may be used in devices such as, e.g., electrical contact switches, hysteresis motors, and other magnetically actuated devices.Preparation of alloys of the invention may be by a treatment of annealing and aging or deformation and aging.

Abstract: In a multipoint data communication system using quadrature-amplitude modulation, a master modem and a plurality of tributary modems are interconnected via respective transmission channels. Adaptive equalizer circuitry in the master modem equalizes the channel from a particular tributary by multiplying samples of signals received from the tributary by an ensemble of tap coefficients associated with the tributary. The tap coefficient ensembles for each tributary are stored in a memory from which they are retrieved at the start of transmission from that tributary. Timing acquisition circuitry within the master modem adjusts the phase of the latter's sampling circuitry at the start of transmission from a given tributary so that the received signals are sampled at the correct time points. In particular, a timing acquisition signal is transmitted by the tributary. The master samples and equalizes the received timing acquisition signal to form a succession of timing acquisition equalizer outputs.

Abstract: A method and arrangement is disclosed for providing a digital conference capability for subscribers of a time division multiplex (TDM) communication system. Each conferee's pulse code modulation (PCM) signal is assigned one of N conference time slots of the TDM system. The arrangement serially stores in memory the PCM signals of N-1 time slots. Circuitry serially generates the sum of the previously stored N-1 time slot PCM signals concurrently with the serial writing into memory of the PCM signal of each time slot. During each time slot a composite PCM conference signal is formed by combining the PCM signal of that time slot with the summed PCM signal and distributed to the conferees assigned to that time slot.

Abstract: Optical fiber switch apparatus for selectively coupling the end (16) of a first fiber (17) to the ends of a plurality of second fibers (10) circularly arranged within a housing (12) also enclosing the free end (16) of the first fiber (17). The latter (17) extends through a spherical bearing (20) seatable in socket (24) formed in the housing (12) end, the bearing having a disc (19) fitted about it at right angles to the axis of the first fiber (17). Arranged around the periphery of the housing (12) is a plurality of piezoelectric bimorph beams (27) having ends slightly below and outside the periphery of the disc (19). When one of the beams (27') is energized, its free end is deflected inward and under the edge of the disc (19). At this time a piezoelectric bimorph plate (33) is energized to deflect its center toward bearing (19) to tilt the disc (19) about a fulcrum presented by the end of the deflected beam against spring clips (22) acting on the housing (12) end.

Abstract: An etching process is described which can etch geometrical shapes on the surface of an n-type or intrinsic compound semiconductor and yield surfaces of optical quality without further processing. The etching process is an electrochemical process where etching is proportional to light intensity. The process involves applying a potential to the compound semiconductor while immersed in an electrolytic solution and irradiating the surface to be etched with light in a certain energy range. The electrolytic solution contains hydrofluoric acid. The distribution of light intensity and ray direction is selected to produce the desired geometrical shape. Particularly advantageous is that the surfaces produced are of optical quality. For example, lenses produced by the etching process exhibit surfaces of optical quality. Further, the process can be carried out on all the lenses on a wafer simultaneously without attention to individual devices. This is highly desirable economically.

Abstract: The dispersive effects of frequency selective fading in a digital, FM, or AM radio system are reduced by means of an adaptive equalizer (11) comprising a cascade of feed-forward stages (1,2, . . . N), each of which includes: a first parallel wavepath (1-1, 1-2, . . . 1-N) including a first adjustable attenuator (20-1, 20-2, . . . 20-N); a second parallel wavepath (2-1, 2-2, . . . 2-N) including a second adjustable attenuator (21-1, 21-2, . . . 21-N) and delay means (22-1, 22-2, . . . 22-N); and means (23-1, 23-2, . . . 23-N) for combining the signals in said wavepaths and for coupling said combined signal to the next stage. By a suitable selection of parameters, according to two unique relationships, a transfer function can be realized which can compensate for amplitude and delay distortions caused by minimum and nonminimum phase fades.

Abstract: Various size frames or pages of information elements stored in a computer system can be simultaneously displayed on a screen-based terminal. The computer processor identifies the screen position the user selects for each of the stored pages and the top-to-bottom order of the pages with respect to visibility in the event that pages overlap. The processor selects the pages in descending order, topmost page first. Information elements of selected pages are transferred to appropriate locations in a display memory only in the event that an auxiliary memory registers that an information element has not priorly been transferred to those locations. After all the pages are transferred, background data is written into each display memory location that the auxiliary memory registers as not having an information element transferred thereto. The display memory is scanned in a conventional manner to apply the display information therein to the viewing screen.

Abstract: A method and apparatus for the transmission of two-tone pictures progressively in several stages. Progressive transmission enables a viewer to receive and utilize pictures in a small fraction of the normal transmission time. In a first stage, information representing groups of picture elements of preselected lines of the scanned picture is transmitted which allows a coarse version of the picture to be reproduced at a receiver. During the subsequent stages the horizontal resolution of the previously transmitted scan lines is improved and additional scan lines are transmitted in a specific order until the received picture is an identical copy of the original picture. The progressive picture information is efficiently transmitted in one of several line-by-line codes resulting in a total transmission time not significantly longer than the time for a nonprogressive transmission.

Abstract: An ohmic contact to a semiconductor device comprising p-type InP is formed by sequentially depositing beryllium-gold and gold layers on InP and then heat-treating the device at a temperature less than 440 degrees C. An ohmic contact to p-type InGaAsP can be similarly formed.

Abstract: Apparatus for generating the inverse or reciprocal of a binary number simplifies the implementation of previous methods. A plurality of registers, a comparator subtractor and a clock circuit are used in combination to modify a long division operation to generate the desired inverse number expeditiously.

Abstract: A procedure is described for electrochemically photoetching n-type and intrinsic compound semiconductors. The process involves applying a potential to the compound semiconductor while it is in contact with an electrolytic solution and irradiating the surface to be etched with light in a certain energy range. By suitable adjustment in the potential, electrolytic solution composition and light energy, the etch rate is made proportional to the light intensity. By suitable variation in light intensity and light-ray direction, various geometrical features can be made on the surface of the compound semiconductor. For example, a hole with straight sides can be made in the compound semiconductor by use of a light spot and parallel (collimated) light rays. An advantageous application of this process is the fabrication of a photodiode with a hole in the center for use in bidirectional communication systems and to monitor power output for optical communication sources.

Abstract: A man-machine interface is disclosed for translating discrete hand positions into electrical signals representing alpha-numeric characters. The interface comprises a glove having sensors positioned with respect to the hand for detecting the flex of finger joints and sensors for detecting the contact between various portions of the hand. Additional sensors detect the movement of the hand with respect to a gravitational vector and a horizontal plane of reference. Further additional sensors detect the twisting and flexing of the wrist. The additional sensors are associated with prescribed mode signals which determine whether subsequently formed or priorly formed character specifying hand positions are to be entered for transmission. The alpha-numeric characters associated with the formed character specifying hand positions are transmitted only when the appropriate mode signal results.

Abstract: In order to provide push-button telephone service to those telephone systems not equipped to respond to multifrequency dialing signals, it is necessary to convert push-button dialed digits into conventional dial pulses. A pulse train consisting of make and break intervals representing the dialed digit is electronically converted (107) into a corresponding series of make and break intervals on the telephone line (102, 103) by switching (106, 108-1, 108-2) a pulsing transistor (101) that is in series with the telephone line ON and OFF. In order to keep the pulsing transistor ON during nondialing intervals and during each make interval, and not attenuate the voice signal, the pulsing transistor is biased by an adjustable current source (105). The current needed to bias the pulsing transistor ON is linearly related to the telephone line current flowing through the emitter-collector path of the transistor, and which varies considerably from station-to-station.