| 摘要 |
A system for receiving remote warning sounds reflected from a roadway surface supporting an automobile includes a sound transducer mounted in the underside of a fender well of the vehicle for producing an audio frequency electrical signal in response to the received reflected warning sounds. The system includes an audio amplifier connected to the sound transducer for amplifying the audio frequency signal. The output of the audio amplifier is connected to inputs of a plurality of tone decoder circuits. Each tone decoder circuit is responsive to an audio frequency signal in a predetermined frequency band. The frequency bands of the plurality of tone decoder circuits are mutually exclusive. Each tone decoder circuit produces an output signal having a first logic level if an electrical signal having a frequency within its frequency range is received from the audio amplifier and a second logic level if no such electrical signal is received. If any of the tone decoders receive an input signal within their respective ranges, a warning light visible to the automobile driver is turned on and a second sound transducer is activated to produce warning sound audible to the automobile driver.
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