| 摘要 |
The emergency vehicle alert system may be used for detection of selected sound frequency signals emitted by warning devices of vehicles. A sensor may sense a selected sound frequency signal spectrum and may be in communication with multiple operational amplifiers. The operational amplifiers may be biased to detect a warning device sound source within 50 feet and within 1,500 feet of the sensor, The detection of a warning device sound source may be communicated to a warning indicator to activate the warning indicator.
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