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SCBA low air alarm with improved voice clarity Disclosure Number: IPCOM000202774D
Original Publication Date: 2010-Dec-31
Included in the Prior Art Database: 2010-Dec-31
Document File: 5 page(s) / 46K

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Williams, Curt: INVENTOR


I propose to keep the characteristic low air alarm sound, but make it dependent on inhalation and exhalation. The standard mechanical knock/bell would be used during inhalation (or not exhaling). This would provide the maximally annoying knock and would distort the codec when no-one is talking. Then, during exhalation or speech (which also requires exhalation) a lower repetition rate knock or no knock can be used, either of which will be much more acceptable to the local and radio voice communication. . This dual-rate alarm will improve radio and face-to-face verbal communication during critical time while the SCBA user is running out of air. This will result in safer operation and improved digital radio satisfaction. . This dual-rate alarm would also provide a second function of notifying other local and radio responders of the breath rate during low air--are they calm, panicking, hyperventilating, etc. If they are calm, others might be running out soon too and should be evacuated too. If they are panicking or disoriented and hyperventilating, they might need a more attentive evacuation.

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SCBA Low Air Alarm with Improved Voice Clarity

By Curtis M Williams Motorola, Inc.

    EMS Research


  Fire fighters, police, and hazardous environment workers rely on radios and SCBA (self contained breathing apparatus) in life threatening situations. The SCBA pack typically has 15-20 mins of air and will emit a low-air-alarm when the air is running low at about 5 minutes remaining. One of the most popular SCBA systems has the alarm attached to the front of the mask and generates audible tones on top of the speech frequencies. This alarm noise runs continuously until the SCBA air is depleted. The noise can make face-to-face speech harder to comprehend, and the alarm will often completely prevent any recognizable words from being transmitted through a standard (P25) public safety digital radio. This interference is obviously problematic during this critical time when the user is running out of air.

  Several radio-based approaches to reducing this alarm interference were investigated and determined to be infeasible, primarily due to relatively stringent standards, regulations, and interoperability requirements. Several SCBA-based

solutions have also been considered and rejected, many due to perceived reduction in the attention-grabbing- nature of the low-air-alarm, changes in the characteristic sound, or greatly increased complexity.

  The solution presented here is to use a dual-rate SCBA alarm which uses a 1/2 frequency alarm during speech and exhalation, and the traditional alarm rate otherwise. This solution strives to satisfy both radio and SCBA design needs. Due to human voice characteristics and codec design parameters a 1/2 rate alarm active during speech moves enough alarm energy away from the speech to allow use of a radio and also improve face-to-face communication. This dual-rate alarm should be very similar and recognizable as the traditional low- air-alarm sound. It would also maintain the attention grabbing characteristic of the alarm with potential to provide additional attention--many modern sirens and alarms, such as emergency vehicle sirens, have been switched from a constant to a changing alarm type in the last twenty years to demand additional attention.

© 2010 Motorola, Inc.

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  This dual-rate low-air-alarm solution to the low-air-alarm speech distortion problem would be highly beneficial for first responders who rely on SCBA and radio equipment in life threatening situations.


  Fire fighters, police, and hazardous environments workers, use SCBA gear for face and lung protection. SCBA gear typically provides 15-25minutes of protection against toxic and/or dangerously hot air. During the course of an incident some users will use enough of their air supply to trigger the audible low- air-alarm (LAA). The responder then may need to use the radio to regroup or retreat.

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