Patents by Inventor Richard J. Lisco

Richard J. Lisco has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 5146079
    Abstract: A broadband optical receiver which exhibits low noise and distortion characteristics. An active bias feedback circuit stabilizes the quiescent operating currents of a low noise amplifier coupled to the receiver photodetector. A transformer matches the impedance of the amplifier to an attenuator.
    Type: Grant
    Filed: November 1, 1990
    Date of Patent: September 8, 1992
    Assignee: AT&T Bell Laboratories
    Inventor: Richard J. Lisco
  • Patent number: 4677632
    Abstract: The power output from a laser transmitter is maintained within predetermined levels. These levels are maintained at fixed percentages on either side of the average laser output power which is transmitted, regardless of variations in ambient temperature. This is achieved by coupling the bias current control loop to the modulation current control circuit.
    Type: Grant
    Filed: October 28, 1985
    Date of Patent: June 30, 1987
    Assignee: American Telephone and Telegraph Company, AT&T Bell Laboratories
    Inventors: Richard J. Lisco, Josef Ocenasek
  • Patent number: 4571506
    Abstract: A driver circuit turns an LED `on` and `off` in response to input logic `one` and `zero` data signals. A current regulator 11 is series coupled with the LED and serves to maintain a constant current to the LED over time, temperature, and supply voltage variations. During turn-off, this current is shunted away from the LED by a low impedance emitter follower (Q3), operated in the active non-saturated region, and a small reverse bias potential is momentarily applied to the LED which quickly sweeps out the charge stored in the LED junction. At the end of the `off` cycle there is a forward prebias potential across the LED. During turn-on, the current shunt is reverse biased and a current peaking circuit (14) provides a momentary additional current through the LED. This instantaneous forward current peaking and the forward prebias both serve to substantially reduce the turn-on delay and rise time of the optical drive signal.
    Type: Grant
    Filed: March 28, 1984
    Date of Patent: February 18, 1986
    Assignee: AT&T Bell Laboratories
    Inventor: Richard J. Lisco
  • Patent number: 4500844
    Abstract: A ringing signal generator is disclosed in which a low-level reference ringing signal, generated by a reference waveform generator (101), is amplified by a delta-modulation power amplifier (106, 108). The low-level reference signal is digitally encoded using delta-modulation techniques to generate a high-level digital signal. The high-level digital signal is filtered (421) to remove the high-frequency components therefrom and to decode the digital signal to form the high-level ringing signal that has the same shape and frequency as the reference signal. The delta-modulation power amplifier generates the ringing signal by comparing (401) the reference ringing signal (E.sub.i) with an analog feedback signal (E.sub.f) reconstructed from the high-level digital signal. The resultant binary error signal (E.sub..epsilon.
    Type: Grant
    Filed: May 20, 1983
    Date of Patent: February 19, 1985
    Assignee: AT&T Bell Laboratories
    Inventor: Richard J. Lisco
  • Patent number: 4336467
    Abstract: A direct current voltage detector is disclosed including a low-pass filter, an isolating diode and a threshold detector. The circuit is designed to be simple and inexpensive and causes no interference with foreign potential and leakage tests on a telephone line.
    Type: Grant
    Filed: January 31, 1980
    Date of Patent: June 22, 1982
    Assignee: Bell Telephone Laboratories, Incorporated
    Inventor: Richard J. Lisco
  • Patent number: 4164713
    Abstract: A detector circuit is shown for detecting off-hook and dial pulse signals in a telephone system which, under the control of a ringing relay, reconfigures itself to provide ring-trip detection. The detection circuit includes a bridge which is responsive to circulating loop currents, while at the same time unresponsive to longitudinally balanced currents, and a two-stage voltage level detector circuit. An RC timing circuit is included between the two stages to insure that the detector is unresponsive to short duration pulses and, at the same time, once energized, will bridge over short duration interruptions of detected pulses.
    Type: Grant
    Filed: October 25, 1977
    Date of Patent: August 14, 1979
    Assignee: Bell Telephone Laboratories, Incorporated
    Inventors: Stephen J. Brolin, Richard J. Lisco, Mark T. Manfred