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Show Keeping Up WitfeScience ifyScfyncb er vice 4S) Science Service. WNU Service, Noiseless Burglars Are Detected by Loudspeaker Alarm Device "Hears" Intruder Before He Makes Sound WASHINGTON. A simplified simpli-fied burglar alarm that "hears" the burglar before he makes a sound, and goes off even before he can get to his safe-cracking tools, forms the subject matter of a patent recently granted here to a New Jersey Inventor. So sensitive is this alarm that should the burglar change the position posi-tion of the tiniest object within the vault room, a warning gong rings and the police dash to the scene. A conventional loudspeaker operated op-erated by a special electric circuit serves as the "ear" of this ingenious alarm. How Alarm Works. Th vibrating diaphragm of the loudspeaker sets up sustained, silent si-lent air vibrations within the In terior of the vault Connecting the loudspeaker to an electrically operated gong-system Is a balanced electrical "bridge." When setting the alarm system to safeguard the vault, this bridge Is adjusted or balanced so that no current cur-rent can flow from the loudspeaker circuit over the bridge to the gong-operating gong-operating circuit. In this condition the loudspeaker diaphragm produces constant vibrations vibra-tions within the vault or room interior in-terior and the gongs are silent. Device Is Sensitive. But let some one open the vault room door, step into' the Interior, make a tiny hole In one of the walls, or as much as change the position of an object In the room, and the nature of the air vibrations is immediately disturbed. Such disturbance dis-turbance breaks down the balanced set-up of the bridge, and starts the alarm circuit where It is detected, amplified and sped to a relay which works the gongs. The inventor claims that his protective pro-tective alarm is much simpler than the present-day systems used in banks, which for complete protection protec-tion require specially designed locks and switches In the doors to control con-trol some alarm device, as well as alarm system networks embedded tn the vault walls and sound pickup pick-up devices In the safes to detect boring and tapping noises. |