Abstract: A communications system includes a Voice over IP (VoIP) device, a plurality of radios each configured to communicate using a plurality of different radio channels, and a bridge radio. The bridge radio includes a VoIP interface configured to communicate with the VoIP device, a radio interface configured to communicate with the radios, and a controller coupled to the VoIP interface and the radio interface. The controller is configured to receive a communication request from the VoIP device to communicate via a given radio channel. The communication request includes an IP address associated with the bridge radio and a channel identifier associated with the given radio channel. The controller also bridges communications between the VoIP device and at least one of the radios over the given radio channel based upon the received communication request.

Abstract: In the manufacture of an MOS gated semiconductor device, indentations are provided on a surface of a semiconductor wafer extending inwardly of respective spaced apart regions at the wafer surface having doping concentrations greater than that present in the remainder of the wafer. A layer of silicon having a doping concentration less than that of the substrate is conformally provided on the substrate surface whereby the indentations in the substrate surface are replicated on the surface of the silicon layer. Dopants in the substrate regions are then out-diffused into the silicon layer to provide highly doped buried regions within the layer. Then, using the silicon layer surface indentations as photomask alignment marks, gate electrode structures are formed on and within the silicon layer in preselected orientation relative to the buried regions. The buried regions provide low resistance paths for current through the resulting devices.

Abstract: A circuit and method for maintaining switch-hook detection (SHD) in the presence of a fault in a telephone system may include a comparison of one of a tip current and a ring current to a reference current. A switch-hook detection indicates that a request for service has been made. The reference current may be a conventional switch-hook detection threshold current, I.sub.SHD, times a factor (G.sub.0 +1).sup.-1, where G.sub.0 is the predetermined operating gain of the amplifier in the telephone subscriber line interface circuit. The line current may be reduced in response to detection of a fault in the telephone system without affecting the determination whether a request for service has being made.

Abstract: A fabrication process for dielectrically isolated high frequency complementary analog bipolar and CMOS transistors. Polysilicon extrinsic bases, polysilicon emitters with sidewall spacers formed after intrinsic base formation provides high current gain, large emitter-to-base breakdown voltage, large Early voltage, and high cutoff frequency.

Abstract: A circuit and method for reducing power consumption during operation of a solid state switch that controls connection of a source of alternating current to a load includes a circuit for determining a voltage across the switch. The switch is operated upon receipt of both a command signal and an indication that the voltage across the switch is less than a predetermined value. When used in a telephone system subscriber line interface circuit (SLIC), the circuit controls two switches that connect an ac ring signal from an ring generator to a telephone. The voltage sensed across the switch may be converted to a low current level and the circuit embodied in an integrated circuit.

Abstract: A digital down converter with a programmable mixing down frequency and a programmable extraction bandwidth uses a Read Only Memory, ROM, based sin/cos generator plus a programmable high decimation filter followed by a gain compensating scaling multiplier and a Finite Impulse Response, FIR, filter. Output format options are also programmable, and programming commands are serially loaded into registers. Various components may be isolated for efficient testing and also subsystem operation.

Abstract: A level shifter for shifting a digital signal input voltage to a digital signal output voltage and for rejecting voltage variations in the level shifter that would cause the level shifter to shift in error. The level shifter includes a trigger for triggering a pulse at each transition of the digital signal between an input supply voltage and an input reference voltage, a latch for switching the digital signal to one of an output supply voltage and an output reference voltage in response to each pulse from the driver and holding the digital signal at that voltage, and two half-shifters connected between the trigger and the latch for providing the pulse to said latch when the digital signal transitions. Each of the half-shifters include a selector circuit with series-connected current mirrors connected to a current source for providing a current to the current mirrors responsive to receipt of the pulse.

Abstract: A method and system for determining whether a transmitting unit is proximate a receiving unit wherein the transmitting unit includes a magnetic field generator for a providing a plurality of time-sequential magnetic fields, each of the sequences being a differential phase shift key (DPSK) modulated code. The magnetic field is transmitted at a relatively interference free frequency of 72 KHz and the DPSK modulation frequency is about 1200 bits per second. Each pair of transmitting and receiving unit uses with a distinguishing code selected from a predetermined group of generally orthogonal codes.

Abstract: A digital down converter with a programmable mixing down frequency and a programmable extraction bandwidth uses a ROM based sin/cos generator plus a programmable high decimation filter followed by a gain compensating scaling multiplier and a fixed FIR filter. Output format options are also programmable, and programming commands are serially loaded into registers. Various components may be isolated for efficient testing and also subsystem operation.

Abstract: A transconductance amplifier suitable for the input stage of a comparator with the capability of amplifying input signal with common mode voltage components in a range including the entirety of its operating voltage. Operation at one voltage extreme is accomplished by use of a long tailed pair connection of a pair of bulk modulated FETs with gates at the input terminals of the amplifier. Operation at the other voltage extreme is accomplished by the use of a pair of FETs in a source follower mode to drive common gate transistors of opposite polarity, the gates of the FETs also being connected to the input terminals of the amplifier. A common high impedance load for the comparator is connected to current mirrors of the drains of both pairs of FETs in the amplifier. The circuit may be implemented with bipolar transistors and additional amplification provided. Methods of comparing voltages are also disclosed.

Abstract: A semiconductor current follower and method using a copy of the input current from a current mirror to insure that the input impedance remains a virtual ground for both unidirectional and bidirectional signals.

Abstract: An optical device and method for sensing a plurality of ambient conditions (e.g., temperature and pressure) may include transmission of an optical flux through a fiber optic cable to a section of the cable that is placed where the ambient conditions are to be sensed. The section of cable includes a plurality of serially aligned sensors for reflecting the optical flux back through the cable, each of the sensors having semi-reflective surfaces at the two ends thereof for partially reflecting the optical flux. The distance between the two ends of each sensor varies primarily as a function of a different one of the ambient conditions. The optical flux is partially transmitted and partially reflected at each of the ends of the sensors and the optical flux reflected back through the cable includes an interference pattern that is a function of each sensor's end-to-end distance. A detector evaluates the interference pattern to determine the ambient conditions.

Abstract: A system and method for storing image data in a location remote from a display device which uses the data. The system uses plural reduced resolution image data sets and geographical coordination between the image being viewed and the data sets to substantially reduce the bandwidth required to transmit the image data and to shorten the time needed for transmission. Automatic transmission of data needed may be utilized.

Abstract: A portable, digital processor-based system equips a craftsperson with the ability to test a subscriber line of a telephone network by accessing a direct test unit (DATU) of a telephone office, said DATU being configured to respond to commands from a telephone test set and to generate audio messages that provide the user with information relating to control of the operation of the test unit for testing a subscriber line, said portable, digital processor-based system having an input/output device, including a visual display, through which information input by the user is converted into tone signals and transmitted to said DATU, and through which information associated with the operation of said DATU is presented by said test device to the user. The displayed information is interactively updated in response to one or more inputs supplied via the input/output device by the user, irrespective of the generation of audio messages by the DATU.

Abstract: A composite thyristor comprising a plurality of parallel connected identical thyristor cells, each of the cells including a turn-on field effect transistor (FET) and a turn-off FET. The gate electrodes of all the FETs form a grid-like pattern on a surface of the semiconductor substrate of the device. The pattern includes strips which intersect at corners. Turn-off FETs are formed along the boundary of the grid and beneath it, and turn-on FETs are disposed beneath the corners.

Abstract: A mechanism for correcting errors in a stream of digital data that are encoded at a transmitter site, transmitted over a communication channel to a receiver site and decoded at the receiver site to recover the digital data pre-encodes the data using a parity-encoder. The location of the errors is determined through a comparison operation on which the receiver is able to generate a `template` of the pattern of errors in the received digital data stream. This error pattern template is then used in an iterative pattern predictive error correction process to identify the location of burst errors contained in the recovered data and to controllably modify the output of the receiver's host decoder so as to remove the located errors from the originally decoded data.

Abstract: A sigma-delta analog-to-digital converter employs multiplexed single-loop modulators in parallel and respectively phased time-divided clocks. The parallel modulators have the effect of producing digital output at a high sampling frequency that is a multiple of the phased switching frequencies applied to the modulator circuits. In one preferred embodiment, four second-order sigma-delta modulators are driven in clocked phased sequence and combined by a multiplexor circuit. Another embodiment employs second-order modulators using RC integrators. A further embodiment replaces the multiplexor with an adder when in-phase modulator clocks are used, and the adder also acts as a simple low pass filter.

Abstract: A splined radial panel solar collector structure approximates compound curvature surfaces by a three-dimensional arrangement of compactly stowable flat reflective panel segments mounted on a collapsible, space-deployable support structure of linear components. The support framework is formed of an umbrella-like framework of radially-extending ribs, struts and cords which deploy away from a central hub to form a system of radial trusses. A semirigid reflective surface structure is divided into sections of radial panels which are supported and shaped by an arrangement of radially tensioned flexible tape members aligned with the ribs. Connecting ties between the tapes and the ribs cause the tapes to assume a catenary curve. The ribs and flexible tape members are bridged circumferentially by sets of cords and ties to which the panels are joined. These cord and tie pairs place the panels in bending to effect a "splined" approximation of a parabola in the radial direction.

Abstract: A linear force actuator system for stabilizing a support structure employs a linear dc motor whose primary winding is driven by a pulse width modulation control signal representative of a force input, through which the secondary member of the motor which acts as an inertial mass, is to be controllably translated. For improved control accuracy, the actuator system of the invention employs a pair of feedback loops, one of which monitors the current in the motor's primary winding to maintain a constant force output to the secondary member and a secondary of which monitors long term deviations from the center of the secondary member and corrects for centering offsets. An opto-electronic position sensing arrangement monitors the movement of the secondary member whereby precise control of commutation of the coils of the primary winding and a smooth translation of the secondary member are obtained.

Abstract: An adaptive brake control system monitors a plurality of brake pipe/air line parameters, such as fluid path volume and air flow rate, and controllably modifies action taken by the engineman or performs emergency control of the brakes, in order to continuously enable the braking system to adapt itself to dynamic operating conditions and anomalies in the integrity of the fluid path. In accordance with a pressure reduction modification mechanism, the application of a pressure reduction to the equalizing reservoir is precisely controlled by taking into account the actual state of the brakepipe, so as to ensure that the requested brake application is effected as intended. The control mechanism also monitors the integrity of the fluid flow path of the brake pipe/train air line, so that the engineman may be alerted and a prescribed train safety measure may be effected in the event of a potentially hazardous anomaly in the link.