MAN-DOWN ALARM SENSOR SYSTEM FOR PERSONAL ALARM RADIO TRANSMITTERS
Original Publication Date: 1988-Oct-01
Included in the Prior Art Database: 2001-Oct-30
Man-Down sensors used in Personal Alarm Transmitters or Transceivers use mercury switches to sense the body motions of the person wearing the unit. The mercury in the switch capsule is continually making and breaking contact as the person wearing the unit goes through normal day to day body motions. The man-down circuitry integrates the constant making and breaking of the mercury contact only producing an output when the circuit is open for a fixed period of time, approximately 5 to 10 seconds. The time constant is compromise between the desire to alert the central station as soon as the event occurs and desire prevent false alarms from normal body motions.