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Publication of BE743691ApublicationCriticalpatent/BE743691A/xx
G08B—SIGNALLING SYSTEMS, e.g. PERSONAL CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
G08B13/00—Burglar, theft or intruder alarms
G08B13/16—Actuation by interference with mechanical vibrations in air or other fluid
G08B13/1609—Actuation by interference with mechanical vibrations in air or other fluid using active vibration detection systems
G08B13/1618—Actuation by interference with mechanical vibrations in air or other fluid using active vibration detection systems using ultrasonic detection means
G08B13/1627—Actuation by interference with mechanical vibrations in air or other fluid using active vibration detection systems using ultrasonic detection means using Doppler shift detection circuits