Abstract: Automatic test pattern generator for generating test patterns that are capable of detecting faults in a digital combinational circuit comprises a first forward network capable of emulating the digital combinational circuit; a second forward network capable of emulating the digital combinational circuit in the presence of any one target fault from a specified set of faults, and receiving a set of control signals for selecting the target fault; a first backward network having one primary input for every primary output of the digital combinational circuit and one primary output for every primary input of the digital combinational circuit, the first backward network generating one fault activation objective corresponding to the selected target fault, and receiving first signal values computed in the first forward network for propagating the fault activation objective towards a primary output; a second backward network having one primary input for every primary output of the digital combinational circuit and one p

Abstract: A boost converter, a method of operating the same and a power converter employing the boost converter or the method.

Abstract: An indoor wireless communications system using two-way active-antenna repeaters to distribute signals received from external signal sources within an office, and to extend the range of cordless phone units in use there, is disclosed. The repeaters provide menu-selectable phase-shifting, selectable receiver sensitivity and transmitter power, and selectable signal format conversion to provide added privacy and to prevent interference with communication links in use by third parties within the building. Pattern selection is done by empirical adjustment of an antenna pattern suited to the general floor plan of the area served.

Abstract: For use with an analog communications device coupled to an analog interface of a digital telecommunications network, the analog interface having signal conversion values corresponding to an n-level symbol table, a system and method that dynamically selects a constellation of symbols from the n-level symbol table, and a modulator/demodulator ("modem") employing the system or the method. The system includes (1)a logic circuit that selects m symbols, m being less than or equal to n, from the n-level symbol table, the m symbols being a function of the signal conversion values, and (2) a transmission circuit adapted to transmit data identifying the m symbols to a remote device digitally-coupled to the digital telecommunications network, the data allowing the analog communications device and the remote device to communicate with a common symbol table dynamically adapted to the signal conversion values of the analog interface of the digital telecommunications network.

Abstract: Devices and methods for speech recognition enable simultaneous word hypothesis detection and verification in a one-pass procedure that provides for different segmentations of the speech input. A confidence measure of a target hypothesis for a known word is determined according to a recursion formula that operates on parameters of a target models and alternate models of known words, a language model and a lexicon, and feature vectors of the speech input in a likelihood ratio decoder. The confidence measure is processed to determine an accept/reject signal for the target hypothesis that is output with a target hypothesis signal. The recursion formula is based on hidden Markov models with a single optimum state sequence and may take the form of a modified Viterbi algorithm.

Abstract: Methods and apparatus for stabilizing or otherwise controlling wavelength in tunable semiconductor lasers and other optical sources. A tunable semiconductor laser includes a gain section and at least one tuning section. Spontaneous emission (SE) from the tuning section is detected and used in a feedback control loop to control the amount of current applied to the tuning section. The SE may be detected using an integrated detector on the semiconductor laser chip, an external detector arranged adjacent the chip to detect SE emitted from a side of the tuning section, or an external detector arranged to detect SE coupled from an optical fiber or other signal line connected to an optical signal output of the laser. The feedback control loop may operate to maintain the detected SE at a constant level, such that the current applied to the tuning section is adjusted to compensate for the effects of aging and the laser output wavelength is thereby stabilized.

Abstract: A microphone/loudspeaker includes a microphone arrangement and a loudspeaker such that the microphone/loudspeaker operates in a quiescent mode and shifts to a speakerphone mode in response to detecting a battery voltage on a telephone line. In the quiescent mode the microphone arrangement and the loudspeaker operate substantially independent of each other while in the speakerphone mode they interact on the basis of their respective signal strengths. In a system, the microphone/loudspeaker is connected to other microphone/loudspeakers so that the microphone arrangement of one microphone/loudspeaker couples in tandem to the microphone arrangement of other microphone/loudspeakers, and the loudspeaker of one microphone/loudspeaker couples in tandem to the loudspeaker of other microphone/loudspeakers.

Abstract: A method shapes traffic using leaky bucket shaping and fair queueing techniques to shape conforming and nonconforming incoming traffic into a compliant output stream on an outgoing link connected to a node. An admitted or arriving cell is assigned to one queue in a set of queues. When a cell reaches the head of its assigned queue, a virtual finishing time is assigned to the cell, even if the cell has not reached its conformance time. A server then selects for transmission on the outgoing link, the head-of-line cell form among the queues with the smallest virtual finishing time. If the server selects a nonconforming cell for transmission, the selected nonconforming cell is rescheduled for transmission. If the selected cell is conforming, it is transmitted on the outgoing link.

Abstract: Photoacid generators advantageous for use in applications such as photoacid generators used in chemically amplified resists are disclosed. These compounds are based on an ortho nitro benzyl configuration employing an .alpha. substituent having high bulk, steric characteristics, and electron withdrawing ability. The enhanced efficacy is particularly found in compounds both having a suitable .alpha. substituent and a second ortho substituent with large electron withdrawing and steric effects.

Abstract: The testing of a series of commands is enhanced using a multilevel approach that employs orthogonal arrays within orthogonal arrays. Specifically, an Orthogonal Array (OA) is applied within each operation and then re-applied across the different operations. Thus, the process initially applies an OA to an intra-operation covering the different combinations of command parameters associated with an operation. The process applies an OA to an inter-operations OA covering the combinations of all command parameters.

Abstract: Techniques for obtaining information about dynamic properties of a program. The techniques involve programming a programmable execution environment such as a debugger so that when the program is executed in the execution environment, side effects of the execution provide the information about the dynamic properties. The program for the execution environment is produced by a source code analyzer which statically analyzes the source code. The source code analyzer is in turn produced by a code analyzer generator. Output from the execution environment may be provided to a graphical display system. In one use of the techniques, the code analyzer generator not only generates a source code analyzer for producing the program for the execution environment, but also a source code analyzer for producing a program which when executed by a graphical browser makes a flow graph for the program.

Abstract: A method and apparatus for estimating individual impulse responses for a stereophonic communication system, such as a teleconferencing system, which involves selectively reducing the correlation between the individual channel signals of the stereophonic system. Selective reduction of stereophonic source signal correlation advantageously results in the estimation of individual impulse responses of a receiving room of the stereophonic communication system. The selectively reduced-correlation source signals are provided to conventional adaptive filters and the receiving room loudspeakers. Automatic echo cancellation is performed in a conventional fashion, but on the selectively reduced-correlation source signals. Specifically, selective reduction of source signal correlation between two stereophonic channels of a teleconferencing system is achieved by introducing a small non-linearity into each channel in order to reduce the interchannel coherence.

Abstract: A method of enhancing predefined features of a scanned image of a document page of reduced size for display includes subsampling the pixels of the scanned image to achieve a desired degree of reduction of the image size. The subsampled signals are passed through a filter to obtain gray scale values. A sharpening filter is applied to the subsampled pixels to enhance the predefined features of the image.

Abstract: A mechanically stable self-aligned M.times.N optical switch having a low insertion loss is achieved by employing three cleaved silica optical structures containing a plurality of waveguides. A monolithic silica optical structure is cleaved into the three corresponding structures. Each of the first and third structures has a cleaved edge and a respective set of waveguides extending parallel to a corresponding structure surface. The second structure has two substantially parallel cleaved edges and a plurality of sets of waveguides extending parallel to a corresponding structure surface. The corresponding surfaces of the first, second and third structures are positioned on, for example, surfaces of respective first, second and third bases aligned in a common plane. The structures are further positioned with the cleaved edges of the second structure arranged adjacent to and facing respective ones of the cleaved edges of the first and third structures.

Abstract: The present invention provides an optical detection system for detecting defects in an optical fiber. The system includes a light source for coupling light into the secondary coating of an optical fiber at a preselected angle with respect to the longitudinal axis of the fiber and an optical detector positioned adjacent the fiber at a preselected distance from the point at which the light is coupled into the fiber coating. In accordance with one embodiment, the light is coupled into the fiber coating at a sufficiently shallow angle with respect to the longitudinal axis of the fiber to cause the light to travel through the coating in a direction substantially parallel to the axis of the optical fiber for some distance before exiting the coating.

Abstract: A signature verification method operates by comparing the numerical values of parameters evaluated on a trial signature with stored reference data derived from previously entered reference signatures. The parameters include global features of the signature, and also include a stroke-direction code (SDC) of the signature. An SDC is derived by subdividing the signature into a sequence of time-ordered, spatially oriented line segments, each segment extending between a pair of discrete points along the signature. Each line segment has a stroke-direction value. The SDC is the ordered sequence of these stroke-direction values.

Abstract: In order to provide reliable backup memory for the operational memory (RAM) of a control unit, two segments of a memory with write protect facility are used. Only one of these segments contains the backup memory at any one time, but the other segment may be updated with a new release. Write protect is removed from one of these segments only when an update is taking place. The software for controlling initialization of the operational memory from the backup memory is stored in the backup memory. Extensive checks are performed before accepting an update of the backup memory or an initialization of the operational memory.

Abstract: A self-tuning optical waveguide filter for attenuating a lower power light signal at .lambda..sub.1 more than a higher power signal at .lambda..sub.2 comprises a length of single core waveguide and a light injector for applying .lambda..sub.1, .lambda..sub.2 into the waveguide in two propagating modes subject to mode beating. The mode beating produces high intensity regions of .lambda..sub.1 physically displaced from high intensity regions of .lambda..sub.2. A portion of the waveguide is doped with a saturable absorber for disproportionately attenuating wavelengths at lower power levels. Advantageously the waveguide is a single-core fiber having its central core doped with rare-earth saturable absorber. In a preferred embodiment, the fiber is dimensioned to propagate .lambda..sub.1, .lambda..sub.2 in the LP.sub.01 and LP.sub.02 modes, and the saturable absorber is Erbium.

Abstract: A method and apparatus for performing adaptive hybrid automatic repeat request (ARQ) coding in which the coding is modified based on the acknowledgements returned by the receiver. In accordance with one illustrative embodiment of the present invention, the state of the channel is implicitly determined by the transmitter based upon the frequency of acknowledgments (ACKs and NACKs) arriving from the receiver. For example, since a NACK implies a weak received signal strength, the code rate of the FEC is advantageously reduced in response to such an acknowledgement. On the other hand, the code rate of the FEC is advantageously increased in response to an ACK. In accordance with another illustrative embodiment of the present invention, the acknowledgement returned by the receiver is modified to convey the number of errors in the corresponding received data packet.