Patents Assigned to Data Distribution Devices, Inc.
  • Receiver for audible alarm
    Patent number: 4617555
    Abstract: A receiver to detect the audio tone emitted by an activated smoke alarm. The receiver employs an electret condenser microphone to monitor ambient sound. The output of the microphone is applied to an active band-pass filter and then to a PLL tone decoder. The PLL is tunable to provide maximum sensitivity to the frequency of the tone. The microphone is the gain controllable element in an AGC system that acts to keep received signals at a constant level. This insures that all devices operate linearly.
    Type: Grant
    Filed: April 17, 1985
    Date of Patent: October 14, 1986
    Assignee: Data Distribution Devices, Inc.
    Inventor: Arthur E. Sheiman