Patents Assigned to John M. Marshall
  • Window security device
    Patent number: 4755800
    Abstract: A window security device which operates on differential gas pressure theory to trigger an alarm upon pressure equalization. A plug which completes the electric activator circuit includes biasing springs or similar devices to urge the plug out of contact with the activator circuit to trigger the alarm upon disturbance or breakage of one of the window glazing panels.
    Type: Grant
    Filed: July 13, 1987
    Date of Patent: July 5, 1988
    Assignee: John M. Marshall
    Inventors: John M. Marshall, Donald D. Snyder
  • Window security device
    Patent number: 4633233
    Abstract: A window security device adapted for use in a vacuum environment. The device includes a conductive seal in electrical communication with an alarm. When the vacuum is disturbed the seal falls out of contact with the alarm circuit, activating the alarm.
    Type: Grant
    Filed: February 19, 1985
    Date of Patent: December 30, 1986
    Assignee: John M. Marshall
    Inventors: John M. Marshall, James D. Hall