Abstract: An optical integrated circuit comprises an optical substrate and an optical waveguide supported by the substrate. A transducer is incorporated into the optical integrated circuit and coupled to the optical substrate. The transducer comprises a region of piezo-electric material and a set of electrodes for applying a voltage to the piezo-electric material for selectively causing the deformation of the piezo-electric material so as to alter the optical path length of the waveguide.

Abstract: A system for performing optical pattern recognition includes a first detector neural network for detecting the presence of a particular optical pattern in an input image and a second locator neural network for locating and/or removing the particular optical pattern from the input image. The detector network and the locator network both comprise nodes which can take on the -1, +1, or undefined states. The nodes are arranged in layers and each node in a layer has a location corresponding to a pixel in the input image. A particular application of this neural network is in finding the amount field on a check and removing the line which borders the amount field.

Abstract: An improved digital parallel correlator is disclosed. Illustratively, the inventive correlator utilizes a shift register which receives a signal comprising data bits encoded as chips. At each cycle of the signal, the chips in the shift register are compared to a reference sequence and the number of matches is obtained. Whenever the number of matches exceeds a fixed high threshold or falls below a fixed low threshold, indicating the presence of a binary 1 or binary 0 data bit, the chips in the shift register are set to a predetermined sequence such as the reference sequence or its complement. This amounts to correcting any chips of a bit that are received in error as soon as it is determined that the bit is a binary 1 or binary 0. This enables the high and low thresholds to be located as far as possible from the peak correlation values thereby increasing the number of chips that can be received in error.

Abstract: A dual mode LMS channel equalizer is disclosed. The inventive channel equalizer utilizes an LMS algorithm to both identify channel parameters and to smooth the received data signal to mitigate the effects of channel additive noise. In real time operation, the inventive equalizer first identifies the channel parameters in a training period. Thereafter, the same LMS algorithm is switched to smooth the received data signal, while intermittently, the LMS algorithm is switched back to track the slowly changing channel parameters. In comparison with the conventional LMS adaptive channel equalizer, the inventive dual mode channel equalizer achieves a significant performance improvement at little additional cost.

Abstract: A circuit and method is disclosed for recovering the transmitter clock at a receiver in a direct sequence spread spectrum communication system where a transmitter and receiver run independent clocks of nominally the same frequency. At the receiver, to select the phase of the local clock that yields the strongest signal, a clock recovery circuitry cycles through M phases of the locally generated receiver clock. The cycling is halted and the phase is locked soon as an indication is obtained that a phase is valid. Alternatively, all M phases of the local clock are tested for validity or invalidity, and depending on the resulting pattern of valid and invalid phases, a particular phase is selected for the local clock. A phase is valid or invalid depending on whether there is a second correlation crossing at the expected instant one data bit period after a first correlation crossing.

Abstract: A method and apparatus for transmitting a stream of data bits in a spread spectrum format is disclosed. The inventive method comprises providing 2.sup.N predetermined spreading sequences, where N is equal to or larger than 2. The predetermined spreading sequences have suitable autocorrelation and cross-correlation properties. For each group of N bits in a stream of data bits to be transmitted, a particular one from the 2.sup.N predetermined spreading sequences is selected and transmitted. In this manner, each transmitted spreading sequence corresponds to a particular arrangement of N bits. The invention achieves an N-fold increase in data rate for a particular symbol rate by encoding N bits in a spreading sequence.

Abstract: An adaptive nonlinear data driven echo canceller is disclosed. Unlike other approaches to nonlinear echo cancellation, the inventive echo canceller treats the nonlinearity of the echo path as nonlinear noise associated with transmitting data symbols through a linear echo path. In comparison to a conventional LMS data driven linear echo canceller, the inventive echo canceller utilizes only an additional small random access memory for storing a nonlinear function for estimating the effect of the nonlinear echo path on transmitted data symbols. The same LMS algorithm is used to estimate the linear echo path and the nonlinear function. The signal processing power of a conventional linear data driven LMS echo canceller is sufficient to implement the inventive nonlinear echo canceller and the convergence speed of the nonlinear echo canceller can be less than three times that of the conventional linear LMS echo canceller.

Abstract: A method for controlling audiotex services which is analogous to the method by which users operate conventional commercial radios is disclosed. In accordance with the inventive method, upon dialing a general audiotex telephone number, the user hears what sounds like the slow changing of stations on a radio. The effect is produced by successively transmitting to the caller a short excerpt from each of a plurality of available audiotex services. The caller may stop the scanning of the audiotex services at any particular audiotex service by pressing a particular key on the telephone keypad. Other keys may be used to resume the scanning of the audiotex services in the forward or reverse directions and at a slow or fast speed. Some of the keys on the user's telephone keypad may be used as memory keys. When a user presses one of these memory keys, access to a particular audiotex service is immediately provided.

Abstract: An injection unit which is associated with a cylinder of a multicylinder diesel engine and comprises an injection nozzle and an injection piston pump which is disposed in a common housing and is driveable by a cam shaft. Said pump comprises a rotatable pump piston which is displaceable in a pump cylinder and has two control edges disposed axially spaced from each other for at least one fuel passage of the pump cylinder. To obtain the desired injection accuracy by accurately observing only a few dimensions during the production and without further tests, measuring and adjusting operations, the pump piston (3) and the pump cylinder (14) each comprise at least one stop face (24, 25) extending transversely preferably normal to the pump longitudinal axis. Said faces cooperate in the basic position of the pump piston (3) assumed in the installation of the unit in the engine directly or indirectly with simultaneous rotational position fixing of the pump piston (3).

Abstract: A transducer free of any magnetic core for contactless measurement of a current includes an electrically conducting strip adapted to carry the current in a predetermined direction. The current thus generates a first primary magnetic field which has a direction at right angles to the predetermined direction near one side of the strip, and a second primary magnetic field near the other side of the strip, which has a direction opposite to the predetermined direction. A first magnetic field sensor near one side measures the first primary magnetic field and provides a first output signal, and a second magnetic field sensor near the other side of the strip measures the second primary magnetic field, and provides a second output signal. A circuit connected to the first and second magnetic field sensor processes the first and second output signals, and generates an output signal proportional to the measured current.