Abstract: An apparatus and technique for providing isolation for a signal source utilizing two or more modulators is described. In particular, the apparatus generates a timed sequence of "open gates" that are synchronized to the data signal which permit transmission in a forward direction, and which attenuate a reverse direction signal. Another embodiment attenuates primarily reflected light signals by utilizing a passive waveguide and a modulator. The passive waveguide provides a propagation delay such that signals reflected from its end facet are attenuated by the modulator. The apparatus is suitable for use as an isolator for a light source in a high-speed optical fiber data transmission system.

Abstract: A microwave arrangement, such as a splitter and combiner, is formed by sandwiching a conductive ground plane between two dielectric microstrip boards whose outer faces carry RF traces and extending the ground plane with a conductive plurality of distributed via holes that contact the ground plane and pass through the boards to their outer faces. Connections are made between the traces on the surfaces with additional conductive via holes that pass through the ground plane where the ground plane forms openings for passage of the via holes.

Abstract: An optical switch device has a plurality of fixed optical fiber terminations supported in a fixed array, and a terminated fiber movable by means of a stepping motor into registry with each of the terminations. Opposite the fixed array is a second array of optical devices oriented such that each termination defines a unique light path with each of the optical devices, with the light paths thus formed being parallel to each other.

Abstract: An echo canceller includes receive and send paths each having an input and output port, a first non-adaptive filter with first filter coefficients for generating a first replica signal in response to a receive input signal, a second adaptive filter with second filter coefficients for generating a second replica signal in response to the receive input signal, a first subtracter for generating a send output signal representing a difference between a send input signal and the first replica signal, a second subtracter for generating an error signal representing a difference between the send output signal and the second replica signal, and a controller for replacing the first filter coefficients by the sum of the first and second filter coefficients and for resetting the second filter coefficients in response to a calculation that includes a first quantity associated with the send output signal and a second quantity associated with the error signal.

Abstract: A method for deadlock recovery in a shared resource multiprocess message passing computer system. The processes executing in the computer system perform periodic local checkpoints and communicate via inter-process messages. Upon detection of a deadlock in the computer system, inter-process rollback dependency is analyzed in order to choose a resource to reclaim. The choice of a resource to reclaim is made such that a resource manager which manages the resource can be rolled back so as to reclaim the resource, and such that an application process which is waiting for the resource is not rolled back past the point at which deadlock was detected. Thus, upon system restart, the reclaimed resource can be provided to the waiting process, and the waiting process can execute past the deadlock point.

Abstract: A device for restricting access to certain programs. The RCU comprises an entry pad, a controller, a read-only-memory ("ROM"), and an transmission system.

Abstract: An echo canceller system includes first and second echo cancellers. Each echo canceller includes a foreground filter and an adaptive background filter, with the foreground filter providing the actual echo cancellation and the background filter updating the foreground filter. The echo canceller system also includes send and receive paths, a shared coefficient memory, and a controller for switching the shared coefficient memory between background filters in response to signals along the send and receive paths. The switching includes resetting the shared coefficient memory to prevent any transfer of filter coefficients between the background filters. The background filters operate one at a time, depending on which background filter has access to the shared coefficient memory, while the foreground filters operate simultaneously.

Abstract: An integrated circuit is disclosed including an analog-to-digital (A/D) converter having an offset source for providing an offset signal; and a first reference array including a plurality of cells for generating a first output signal from an input signal and the offset signal, for generating a second output signal from the offset signal, and for generating an A/D output signal from the first and second output signals.

Abstract: A method and apparatus for concurrent communication of analog information and digital information. In general terms, when the communication channel is viewed as a multi-dimensional space, the digital information signal is divided into symbols, and the symbols are mapped onto the signal space with a preset distance between them. The analog signal, generally limited in magnitude to less than the distance separating the symbols, is converted to component signals and added (i.e., vector addition) to the symbols. The sum signal is then transmitted to the receiver where the symbols are detected and subtracted from the received signal to yield the analog signal components. The transmitted analog signal is recreated from those components. Both half-duplex and full-duplex operation is available in accordance with the disclosure.

Abstract: A method for automatically transferring customer data among a plurality of central office switches comprises receiving a work order message from a central provisioning system at a message directing switch. The message directing switch is in communication with at least one message receiving switch in a local telecommunication network. Upon determining that a particular work order message received from a central provisioning system requires a coordinated data transfer, a data query is formulated in the message directing switch to retrieve specific data, such as data relating to a customer directory number, from a message receiving switch. Once the data is received in the message directing switch, the data is processed and retained in the message directing switch or delivered to another switch in the telecommunications network. The method and system alleviates the need for manual retrieval and installation of specific customer line data when a directory number is moved from one central office switch to another.

Abstract: This invention relates to the use of a standard language and signal interface between a custom line card for connection to a corresponding arbitrary type terminal, and a switch. The line card is plugged into an interface unit which converts between the signals from the arbitrary type terminal and a standard set of signals for interfacing with the switch. The Bellcore TR303 standard is the preferred choice for communicating signals between the interface unit and the switch. The term terminal as used herein is very general and includes both simple (analog) and complex (video) telephone devices, as well as other types of customer premises equipment such as FAX terminals; it includes, for example a TV set-top box. Advantageously, only a small signal conversion program and table, and an interface card, need be developed in order to support a new type of terminal.

Abstract: Method and apparatus are disclosed for deinterlacing of an interlaced video frame sequence using interpolation estimations, such as spatial and temporal interpolations. Interpolations requiring a less accurate estimation of missing pixel values in the frames being deinterlaced, such that an interpolation may be performed with a minimum of error, are performed before interpolations which require a more accurate estimation of missing pixel values for performing an interpolation, such that estimates of missing pixel values are obtained with a minimum of error. Interpolation estimations are weighted in combination for computing approximations of missing pixel values in accordance with the errors associated with the respective interpolations.

Abstract: A lightwave communication system includes an optical distribution system for routing optical signals and a plurality of optical transmitters coupled to the optical distribution system. At least one of the optical transmitters has an amplified light emitting diode for generating an optical spectrum. At least one optical receiver is optically coupled to the optical distribution system.

Abstract: Batteries based on lead chemistry, e.g., lead-acid batteries, are substantially improved through the use of a particular positive material. This material is formed by the electrochemical conversion of tetrabasic lead sulfate (TTB) where this TTB is synthesized at a pH in the range 9.3 to 12 and under reaction conditions that provide a substantial excess of sulfate to the reactive lead. The resulting materials provide needle-like structures with a width generally in the range 3 to 1 .mu.m. The relative narrow needles, when employed on the positive electrode of a lead acid battery, improve the efficiency of formation, provide good adhesive to the positive plate, extend battery life, as well as, yield excellent capacity per gram of active material.

Abstract: The specification describes a comparator circuit especially designed for high speed applications such as lightwave systems. The comparator is compensated for offset voltages due to current leakage and other variations in the IC components.

Abstract: Query optimization which is done by making a graph of the query and moving predicates around in the graph so that they will be applied early in the optimized query generated from the graph. Predicates are first propagated up from child nodes of the graph to parent nodes and then down into different child nodes. After the predicates have been moved, redundant predicates are detected and removed. Predicates are moved through aggregation operations and new predicates are deduced from aggregation operations and from functional dependencies. The optimization is not dependent on join order and works where nodes of the graph cannot be merged.

Abstract: A computing interface system includes a mouse with a keypad, and a computer display that displays a group of icons that have a one-to-one correspondence to the keys composing the mouse's keypad. The icons have the same relative positioning as the keys composing the mouse's keypad. This arrangement permits the user to enter digits into the computer without repeatedly shifting his or her gaze back and forth between the keypad and display.