Abstract: A multi-mode modem and a method of transmitting data utilizing the multi-mode modem are disclosed in which different modes of operation may be automatically selected by sending multiple link requests to a receiving modem in order to provide either optimized or non-optimized data transmission according to line conditions.

Abstract: The present invention involves a device for synchronizing the broadcast frequency of a base station and a microcell linked together by a metallic medium as well as a method for using the device to synchronize the base oscillator and the microcell oscillator. The device comprises a base transmitter which transmits a base time-of-day signal to a microcell comparer, and a microcell clock which sends a microcell time-of-day signal to the microcell comparer. A microcell oscillator provides the microcell clock with a reference frequency. The microcell comparer calculates a time difference which represents a time difference between the base time-of-day signal and the microcell time-of-day signal. The microcell comparer then outputs a correction signal to a digital controller. The digital controller adjusts a microcell oscillator according to the correction signal.

Abstract: A device for simplifying transmission of analog signals received from sensors to a remote station in accordance with the invention includes at least one local electronic module including in combination a modulator for oversampling each analog signal and converting each oversampled analog signal into lower resolution digital words and a transmitter for transmitting the lower resolution words as a bit stream on at least one first transmission channel; at least one synchronization element producing a clock signal allowing synchronization of each modulator with the remote station; and at least one reception module in the remote station including a receiver for receiving the transmitted lower resolution words as a bit stream and a digital filter, coupled to the receiver, for converting each received bit stream received into digital words of a higher resolution (typically 16 or 24 bit words. The invention is useful for transmission of seismic data.

Abstract: A selective call radio frequency (RF) communication device (105) includes a receiver (203) for receiving and converting an RF signal into a converted signal. A controller (206) generates binary message information, a synchronization command signal and an address detection signal. An alert device (207) indicates the receipt of the message information. A frequency counter (427) measures the frequency of the converted signal and also determines the associated binary state of the binary message information. A measurement memory (439) stores the converted signal frequency measurements. The frequency control generator (440) generates a frequency control signal in response to the synchronization command signal being generated. The frequency control signal is a function of the stored converted signal frequency measurements and the associated binary states.

Abstract: A system and method for asynchronously transmitting data blocks, in parallel, across multiple fibers in a serial manner. Frame groups are provided as a mechanism to transmit associated data serially on each fiber and tie the data being transmitted together. The frame groups do not have sequence numbers, therefore, the receiver determines which frames are part of a frame group by the arrival times of the individual frames. The transceivers for each member of the parallel bus asynchronously achieve synchronism from either end of the fiber. Thus the need for a common clock is eliminated. The receivers on each side of the bus determine the relative skew for each conductor by performing skew measurements on a calibration message generated by the transmitters on the other side of the bus. When the skew on all conductors, viewed from both sides of the bus, has been determined, the skew values are exchanged across the bus, thus enabling the transmitters to set proper frame spacing.

Abstract: In a Digital Data System (DDS) a method and apparatus for providing multipoint multiport service. Differences in time delays through the network are compensated by an alignment training wherein the delays from each remote station are measured at a Central station. The Central station determines how much delay to insert at each remote station and then instructs the remote stations to insert the delays. This allows all inbound data to be aligned in time so that when the data are combined within the network by the Multipoint Junction Units (MJU) data errors are not produced. Aligned frames are combined in the MJU operating in data mode in a logical AND operation so that marks transmitted by inactive ports are combined with data from active ports to produce a composite signal which is passed to the Central DSU.

Abstract: A method for marshalling an additional outstation (3) of a time division multiple access (TDMA) telecommunication system including a basestation (4) and a plurality of outstations (1,2), such as a passive optical network (PON). A sequence is transmitted from the additional outstation (3) to the basestation (4) at a level below the noise sensitivity of a receiver (49) of the basestation (4), detected at the base station and its phase determined by a correlation process. From the phase the loop delay to the additional outstation is determined and the outstation instructed to realign its transmission accordingly. The sequence is a short length sequence and the correlation can be performed by a binary division search method or a lowest common multiple method (FIG. 1).

Abstract: In digital transmission, the combination of transmitted pulse shape and receiver sampling time that maximizes the magnitude of the channel output pulse sample is determined. The transmitted pulse shape is represented as a linear combination of orthonormal functions. The coefficients that multiply each of the functions are determined by measuring at the receiver and transmitting back to the transmitter the response of the channel to each independently transmitted function at an approximation to the optimal sampling time. A pulse shape is formed using the calculated coefficients and is transmitted to the receiver where the timing of its maximum is determined, which represents a next approximation to the optimal sampling time.

Abstract: A frame alignment method and system for communicating frames of information between at least two devices. A `start of alignment sequence` is used to cause a device that is in the misaligned state to inform the other device of this state condition in such a way that the other device itself is caused to transition to the misaligned state. The `start of alignment sequence` is therefore a frame alignment error when a device is in the aligned state. Each device in the misaligned state repetitively transmits the `start of alignment sequence`. Each device in the misaligned state transitions to the realignment state upon detection of the `start of alignment sequence`. When in the realignment state the device transmits the `end of alignment sequence` to cause the other device to transition to the aligned state if the other device is in the realignment state.

Abstract: An apparatus and method for extending the range of a digital data network by enhancing skew control. The apparatus is a circuit for use in a network interface unit. The apparatus measures the distance of the network interface unit from the head-end retransmission unit of the network by transmitting a series of signal packets on the network and counting the time it takes for the packets to be received back at the interface unit. All transmissions on the network take place with reference to a timing mark transmitted by the head-end unit at a regular interval. The apparatus sends the first in the series of signal packets at a pre-determined pre-skew interval before the timing mark. The apparatus counts the number of clock cycles after the timing mark before the signal packet is received back at the network interface unit.