Patents Assigned to Atlantic Telephone and Telegraph Company, AT&T Bell Laboratories
  • D.C. voltage converter with overload protection
    Patent number: 4754386
    Abstract: In a d.c. voltage converter 1 including a series arrangement of a transformer 3 and a pulse-switched current source 7 the power converted by means of the transformer 3 is kept constant with the aid of a control circuit 13. In the event of a short-circuit in one of the secondary windings 5-1, 5-2 a voltage drop across an auxiliary winding 6 of the transformer 3 is used to limit the converted power during the short-circuit.
    Type: Grant
    Filed: May 22, 1987
    Date of Patent: June 28, 1988
    Assignees: Atlantic Telephone and Telegraph Company, AT&T Bell Laboratories, Philips Telecommunications BV
    Inventor: Jan De Weerd
  • Expanded partial response processing for analog signal enciphering and the like
    Patent number: 4754481
    Abstract: Partial response signal processing is applied to samples of an analog signal quantized in an amplitude range having a sufficient number of levels that a sample amplitude error of a small percentage of the total levels of the range is not readily perceptible to the human auditory function and that it exhibits tolerable quantizing noise. Samples received into the processing in a transmitting station are sample masked for privacy enciphering. Complementary processing is employed for a receiving station.
    Type: Grant
    Filed: June 24, 1985
    Date of Patent: June 28, 1988
    Assignee: Atlantic Telephone and Telegraph Company, AT&T Bell Laboratories
    Inventor: John C. Feggeler