Siren detector
First Claim
1. An audio range siren detector comprisingaudio pick-up means for transducing variable frequency audio signal energy into variable frequency electrical signal energy,narrow band signal producing means responsive to said audio pick-up means to produce separate outputs when predetermined closely spaced fundamental siren frequencies appear in said electrical signal energy,gated control means responsive to the signal producing means only upon pre-determined reduction of outputs therefrom within a limited time following initiation of any such output, andutilization means responsive to said gated control means.
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Abstract
An audio range siren detector utilizes an audio pickup including an A.G.C. amplifier, a plurality of electronic active filters having closely spaced resonant frequencies such as 800, 825, 850 timing means responsive to an actuating signal from one of the filters for generating a time slot signal of short duration, gating means responsive to each of the filter means for producing an actuating signal, control logic responsive to the occurrence of all actuating signals within the time slot to produce output denoting a valid siren signal, and relay means for setting traffic lights to emergency condition.
The detector includes counters and additional timers to further restrict the conditions under which a valid siren signal will be responded to in order to better discriminate against extraneous ambient noises of all types.
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Citations
8 Claims
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1. An audio range siren detector comprising
audio pick-up means for transducing variable frequency audio signal energy into variable frequency electrical signal energy, narrow band signal producing means responsive to said audio pick-up means to produce separate outputs when predetermined closely spaced fundamental siren frequencies appear in said electrical signal energy, gated control means responsive to the signal producing means only upon pre-determined reduction of outputs therefrom within a limited time following initiation of any such output, and utilization means responsive to said gated control means.
Specification