Abstract: A call answering system or device for a telephone network provides a mechanism for an outbound message (typically a greeting in a call answering scenario) to be identified as semi-interruptible. An attempt to skip over a semi-interruptible message activates a warning message to alert the caller of the special status of the message. The caller may then choose to resume listening to the original message, or confirm their decision to skip it.

Abstract: A data pulse receiver for detecting and amplifying serial data pulses received at gigabit-per-second rates over a transmission medium through which the signal levels have been substantially attenuated. The receiver, in a preferred embodiment, has grounded base differential amplifiers to give impedance matching, signal amplification and wide frequency bandwidth. A regenerative flip-flop with programmable tail current provides hysteresis in order to suppress unwanted noise signals. The flip-flop also returns the data pulses to NRZ format. The receiver may also include means for automatic adjustment of the hysteresis level.

Abstract: A multi-quantum-well Mach-Zehnder optical phase modulator selectively generates positive and negative frequency chirp. The modulator has an asymmetric input y-junction coupler and an asymmetric output y-junction coupler joined by interferometric arms defining two optical paths of unequal length so as to generate a fixed phase difference of .pi. or an integral odd multiple thereof. The modulator has electrodes on each arm for receiving modulating electric fields in a push-pull relationship. A control electrode is provided on one of the arms for receiving a control electric field. The modulator, when driven without any control electric field generates negative frequency chirp, and selectively generates positive frequency chirp in response to adjustment of the control electric field. As an alternative, the length differential between respective arms can be selected to generate a phase difference of .pi./2, in which case control electrodes are required on each of the interferometric arms.

Abstract: A transconductance amplifier for use in a low noise, microwave voltage controlled oscillator. The transconductance amplifier incorporates a linear amplifier having ratioed transistors to provide linearized gain. A tuning arrangement combines in-phase and out of phase currents in an inverse ratio to provide a constant D.C. current sum. The tuning circuit has been arranged to operate without a cascode stage such that the power supply voltage requirement is reduced from 5.0 volts to 3.3 volts.

Abstract: A clock recovery circuit includes a resonant circuit which has a varactor diode and is driven into oscillation at a variable frequency in response to a control voltage fed to the varactor diode. Basically, the resonant circuit is tuned into the clock frequency of an incoming binary data signal. The clock recovery circuit provides a clock signal which is associated with a data output signal. The desired transition timing of the clock signal is at mid-point of the incoming binary data signal. When the transition timing is advanced or delayed from the mid-point due to changes in the resonant frequency of the circuit, the control voltage changes, with the result that the tuning frequency of the resonant circuit is varied. In response to the change of the resonant frequency, the transition timing of the clock output signal is delayed or advanced. This condition is detected and the control voltage fed to the varactor is changed, resulting in achievement of correct transition timing.

Abstract: A telephone caller is permitted to retrieve his call from the central voice services feature of an unavailable called party, and resume the call progress by substituting a calling feature of his own. In a telephone system including a telephone switching facility and a voice features server, provision is made for enabling a calling party to invoke an appropriate calling party feature such as a ring back feature or an override feature, and thereby subsequently achieve a real time conversation with the called party instead of simply being able to leave a voice message for the called party.

Abstract: A key telephone system (KTS) or a telephone private branch exchange (PBX) card is integrated into a personal computer to provide telephone system features. The telephone card includes a call controller, a switching network and an interface bus controller for coupling data signals between the PCI bus and an internal bus of the call controller whereby the telephone card is able to communicate with resources of the PC such as a LAN and a hard disk bulk memory for executing telecommunications functions. In this arrangement the PCI bus must carry both asynchronous data processing and control signals as well as reformatted synchronous signals. The addition of a synchronous bus for transporting synchronous signals is used to couple these signals between the switching network, a telephony features controller and the hard disk bulk memory. The use of the synchronous bus provides for improved telephone traffic capacity and PC functionality.

Abstract: The eligibility of all bidirectional links interconnecting a plurality of nodes in a network is determined based on the free bandwidths in both directions of the links and the bandwidth required for transmitting messages between a source node and a destination node in the network. The determination is exercised as to both ends of a link. Then, the link is determined whether or not it is eligible to become part of the shortest route. The determined eligibility of the links may provide a rapid shortest route selection, which will be executed later, because the route selection steps are not executed for ineligible links.

Abstract: Disclosed is a design detail for an innovative time multiplexed read port architecture implemented as part of a high-speed 9-port time slot interchange random access memory. It provides a practical, high-speed, low-power and area efficient read port structure to allow eight random access reads per clock cycle. Because all timing is internally generated from a single rising clock transition of a system clock signal, no special control or clocking is required externally to the memory.

Abstract: An optical waveguide cross-point switch capable of full broadcast and strictly non-blocking operation. The device has a matrix of a plurality of input waveguides and a plurality of output waveguides (M.times.N). A reflecting surface associated with each intersection may be selectively activated to direct an optical signal on the input line to the associated output line. The reflecting surface may also be employed so as to convert an M.times.N matrix into a 2 (M.times.N) rearrangeable cross-point switch. Each waveguide is capable of switching a data rate of 10 Gb/s or more. For example, with eight wavelength channels used to impart optical signals to a 16.times.16 switch a data rate of 1.28 Terabits/second is achievable.

Abstract: An apparatus includes an IC chip with a signal transmitter and an IC chip with a signal receiver, both chips being mounted on a printed circuit board and being connected via conductors on the board. The signal transmitter has a voltage-current converter and a high output impedance current amplifier. The signal receiver has a current-voltage converter. The voltage-current converter converts the voltage of the digital signal to current which in turn is amplified by the high output impedance current amplifier. The amplified current flows via the conductors in the receiver. The digital signal is transferred via the conductors on the current basis. Due to the transmission of the digital signal of current from the signal transmitter to the signal receiver via the conductors, signal spikes while transmitting are reduced and noise immunity is improved. Also, EMI (electromagnetic interference) emission is reduced and power dissipation is small.

Abstract: A digital controller for an injection laser diode. The controller maintains the laser diode average and peak power levels constant in spite of temperature and/or aging effects. A pseudo-random sequence is superimposed on the `0` and/or `1` current levels to the laser diode and the optical output is detected by a back facet monitor. The detected signal is compared with preset references and a feedback signal is used to control both the bias current and the modulation current.

Abstract: A method of accurately controlling the depth of etched gratings in uniform or layered quaternary III-V material. A native oxide is selectively grown on the area of the quaternary to be patterned and this native oxide is subsequently removed to engrave the surface. Periodic repetition of the oxide growth/removal steps results in gratings of the desired depths.

Abstract: A multi-port SRAM (static random access memory) core array has a core cell with a single-ended, pseudo-differential write access port and differential, indirect access read ports. The architecture of the features of the multi-port SRAM core array allows direct scaling of the number of write and read access ports to any practical limit with no adverse effects on cell stability margins and therefore data integrity.

Abstract: A fully differential distributed amplifier for providing a high frequency, high power output. The inherent base-collector capacitance of the output power transistors of each distributed amplifier is matched with on-chip inductances to create artificial transmission lines for both the input and output paths. The distributed amplifier circuit may be used as a driver for a Mach-Zehnder optical modulator. In this application an output of 3 V peak-to-peak per modulator arm is delivered at 10 Gb/s.

Abstract: A programmable wavelength discriminator for isolating individual wavelength carriers from an optical signal including a plurality of wavelength carriers. The discriminator preferably has a pair of waveguides, with each waveguide having imprinted therein a reflecting grating whose period is chosen to reflect the wavelength to be isolated. A receiver such as a photodetector interrogates the selected wavelength. A programmable optical switch determines through which waveguide the composite optical signal will travel. A method of isolating discrete wavelengths from an optical signal comprising a plurality of wavelengths is also discussed.

Abstract: An analog switch matrix provides limited connectability between a plurality of n telephone line appearances and a lesser plurality of m line interface circuits each connected with a communication path in a telephone system. The analog switch matrix includes n groups of 3 crosspoints each being operable to connect and disconnect a one of the n telephone line appearances at any of 3 line interface circuits, each of which is connectable to more than three of the line appearances. A switch matrix controller directs switching operations of the analog switch matrix in response to transitions to OFF HOOK states having been sensed at line appearances and in concert with the call controller in the telephone switching system. In a telephone system with a concentration ratio of 4:1 the grade of service is maintained by performance of a call transfer between ones of line interface circuits at any time during a call progress.

Abstract: A multi-wavelength laser array having a plurality of gain-coupled distributed feedback ridge waveguide lasers. The operational wavelength of each laser is established by selecting a width of the ridge waveguide in the range 1.6 .mu.m to 5.2 .mu.m. Fine tuning of each central wavelength is achieved by thermal power to selected waveguides via Titanium thin film resistors integrated into the laser array. A wavelength range of 9 nm is demonstrated utilizing a sixteen element array.

Abstract: A Mach-Zehnder optical modulator in which the chirp parameter can be varied by adjusting the optical power splitting ratio between the two arms of the interferometer. The modulating voltage is supplied to a single arm or alternatively to both arms in a push-pull configuration. For an appropriate power splitting ratio negative chirp is achieved with approximately equal push-pull modulating drive voltage. This results in optimum distance and bit rate characteristics with low drive power.

Abstract: A polarization independent tunable filter/receiver for optical communications. The tunable filter, operating as a directional coupler, has three waveguides including a central, feedguide and a pair of branch waveguides. Through either electro-optic effects or free carrier injection, the TM and TE polarization modes of the central wavelength can be coupled from the feedguide to the appropriate branch guide. The separated modes can be either detected independently or reunited in phase for further processing.