Patents Assigned to Winster Engineering Group Limited
  • Intrinsically safe telephone systems
    Patent number: 4064366
    Abstract: An intrinsically safe telephone system for use in mines or similar hazardous areas including a battery charging circuit arranged to supply charging current of a predetermined low value to the battery of an operational unit located in the hazardous area during on-hook periods. A circuit is provided for modulating the charging current below the predetermined value to generate both the incoming and outgoing call signals during signaling periods.
    Type: Grant
    Filed: January 15, 1976
    Date of Patent: December 20, 1977
    Assignee: Winster Engineering Group Limited
    Inventors: William Wheatley, Robert Roy Goff, William Charles Wheatley