ULTRASONIC EMERGENCY CALL SYSTEM

摘要

An ultrasonic emergency call anti-agression system designed to indicate in which exact room a person requiring urgent help is located within a building. An ultrasonic receiver is installed in each room under surveillance. A miniature portable ultrasonic transmitter is distributed to personnel required to work in high risk areas. The miniature transmitter is equipped with a switch which, when activated, automatically transmits ultrasonic signals for a 20 second period. The signal activates only the receiver installed within the room where the person is located. Because of the transmission characteristics of the ultrasonic frequencies, the receivers installed in adjacent rooms are not activated. Each receiver is connected via a two pair cable to a control center equipped with an alarm board. Upon reception of an exact ultrasonic frequency signal tasting for a minimum of one second the receiver relay is activated and the room corresponding light is turned on at the alarm board. The system can also be interfaced with an automatic numeric/alphanumeric display radio paging system for prompt intervention. After every activation the transmitter emits for 20 seconds to ensure that the receiver is triggered even if the person is being molested or the transmitter has been snatched away from her during an agression.