Methods and apparatus for electronically detecting siren sounds for controlling traffic control lights for signalling the right of way to emergency vehicles at intersections or to warn motor vehicle operators of an approaching emergency vehicle
First Claim
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1. An apparatus for electronically detecting valid siren sound emitted from an emergency motor vehicle having a sounding siren, said siren being characterized as emitting loud, audible frequencies that cyclically vary with time between a high “
- B”
frequency to a low “
A”
frequency for sounding a warning siren sound, said siren being characterized as being rich in harmonic overtones, comprising;
means for receiving said siren sound frequencies and converting the received sounds to corresponding electrical signals,first operational amplifier circuit means coupled to said receiving means and amplifying the electrical signals coupled thereto and filtering out any high frequency signals,second operational amplifier circuit means having input and output terminals,circuit means coupled to the input terminals of said second amplifier circuit means for biasing said amplifier means in a near oscillatory mode at a pre-selected frequency above the frequency of the high frequency end or “
B”
frequency of the siren frequency range,feedback circuit means comprising a parallel circuit means network of a resistor and capacitor connected between the input and output terminals of second amplifying means, said feedback capacitor being selected and proportioned for stabilizing said second amplifier means for preventing said amplifier means from going into oscillation at said frequency above the siren frequency range and thereby causing said input circuit means for second amplifying means to function as a band pass filter that is frequency band limited to said siren sound frequencies applied to said second amplifying means,a frequency adjustable, phase lock detector circuit means arranged for detecting pre-selected frequencies including a pre-selected frequency range below said high “
B”
frequency and a frequency range above said low “
A”
frequency for locking said detector circuit means to said pre-selected frequency below said “
B”
frequency and providing an electrical output signal representative of said locked condition upon receipt of said signal below said high “
B”
frequency,said phase lock detector circuit means being coupled to a frequency setting network for setting said detector circuit means to said pre-selected high frequency, said frequency setting network comprising a combination of resistor and capacitor means for defining said pre-selected high frequency for said detector circuit means,said detector circuit means causing the lock up of said detector circuit means upon receipt of a signal having said pre-selected high frequency and causing the unlocking thereof upon the signal undergoing processing decreasing in frequency,resistor ladder network means including an individual resistor means continuously connected in combination with said frequency setting network for defining said pre-selected frequency for locking said phase lock detector, as the siren signals decrease from said pre-selected high “
B”
frequency to said pre-selected low “
A”
frequency,timing circuit means for timing a pre-selected time interval between the locking and unlocking periods of said phase lock detector circuit means and coupled to the output signal for said phase lock detector for initiating the timing period upon detection of a locking frequency,a binary coded decimal counter having input terminals and binary coded decimal output terminals,an input terminal for said counter being coupled to be responsive to said output signal for said phase lock detector upon receipt of a locking signal frequency for enabling said counter to count up, said output terminals for said counter providing binary coded decimal signals representative of the counters'"'"' count, said counter having a pre-selected total decimal count,multiplexing circuit means coupled to pre-selected output terminals of said counter and to said ladder network and providing an individual output count signal corresponding to the decimal count of said counter in response to the receipt of said inputted binary coded decimal signals, and effective to serially select and add a corresponding resistor or resistors from said ladder network for defining a lower high “
B”
frequency as the input signals coupled to said detector circuit means decrease in frequency, the “
zero”
output count of the counter causing a pre-selected resistor of said ladder network to be continuously connected in combination with the frequency setting network for determining the pre-selected high frequency below said “
B”
frequency lockout frequency of said phase lock detector circuit means,the decreasing frequencies of the input siren signals causing said phase lock detector circuit means therefrom upon the unlocking thereof that is coupled to said counter input terminal and causes said counter to count up one decimal count for each lock-unlock sequence that occurs during the pre-selected time interval of said timing circuit and thereby causing an additional resistor or resistors to be added to said pre-selected resistor of said ladder network to said frequency setting network for defining a lower frequency for said detector circuit means, upon said counter counting up to said pre-selected count, the counter directly provides an output signal representative of the complete tracking of the siren signal from said pre-selected high “
B”
siren frequency to the low “
A”
frequency incrementally in accordance with the total decimal count selected for said counter, and means coupled to said output signal representative of the complete tracking of the siren signal from said “
B”
frequency to said “
A”
frequency for signaling the detection of a valid siren sound signal.
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Abstract
A siren sensor for detecting siren sounds emitted from emergency vehicles and electronic processing circuits for detecting and identifying the siren sounds electronically to control the traffic signal lights at an intersection to permit only the emergency vehicle to travel through an intersection with the right of way. The method and apparatus utilizes an acoustic horn in combination with a microphone for receiving the siren sounds and converting them to corresponding electrical signals. A conventional horn is modified to function as an acoustic lens to filter and amplify the siren sounds applied to the microphone. The modified acoustic horn and microphone combination comprise a tuned and directional audio sensor sensitive in the frequency range of an emergency vehicle siren. The electronic signal processing circuitry amplifies the resulting microphone signals to obtain the maximum sensitivity to the frequency spectrum of siren sounds. Detectors tuned to a harmonic of the siren signals is utilized for eliminating extraneous sounds along with unique filtering to band pass only sounds in siren frequency spectrum to a phase locked loop detector. The validity of the detected signal is verified by tracking a portion of the siren signal in pre-selected increment under time constraints to lock up and unlock the detector to verify a valid siren sound signal has been detected and provides a valid output signal for use in controlling a conventional traffic light sequencing control or to warn a motorist of an approaching emergency vehicle.
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Citations
8 Claims
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1. An apparatus for electronically detecting valid siren sound emitted from an emergency motor vehicle having a sounding siren, said siren being characterized as emitting loud, audible frequencies that cyclically vary with time between a high “
- B”
frequency to a low “
A”
frequency for sounding a warning siren sound, said siren being characterized as being rich in harmonic overtones, comprising;means for receiving said siren sound frequencies and converting the received sounds to corresponding electrical signals, first operational amplifier circuit means coupled to said receiving means and amplifying the electrical signals coupled thereto and filtering out any high frequency signals, second operational amplifier circuit means having input and output terminals, circuit means coupled to the input terminals of said second amplifier circuit means for biasing said amplifier means in a near oscillatory mode at a pre-selected frequency above the frequency of the high frequency end or “
B”
frequency of the siren frequency range,feedback circuit means comprising a parallel circuit means network of a resistor and capacitor connected between the input and output terminals of second amplifying means, said feedback capacitor being selected and proportioned for stabilizing said second amplifier means for preventing said amplifier means from going into oscillation at said frequency above the siren frequency range and thereby causing said input circuit means for second amplifying means to function as a band pass filter that is frequency band limited to said siren sound frequencies applied to said second amplifying means, a frequency adjustable, phase lock detector circuit means arranged for detecting pre-selected frequencies including a pre-selected frequency range below said high “
B”
frequency and a frequency range above said low “
A”
frequency for locking said detector circuit means to said pre-selected frequency below said “
B”
frequency and providing an electrical output signal representative of said locked condition upon receipt of said signal below said high “
B”
frequency,said phase lock detector circuit means being coupled to a frequency setting network for setting said detector circuit means to said pre-selected high frequency, said frequency setting network comprising a combination of resistor and capacitor means for defining said pre-selected high frequency for said detector circuit means, said detector circuit means causing the lock up of said detector circuit means upon receipt of a signal having said pre-selected high frequency and causing the unlocking thereof upon the signal undergoing processing decreasing in frequency, resistor ladder network means including an individual resistor means continuously connected in combination with said frequency setting network for defining said pre-selected frequency for locking said phase lock detector, as the siren signals decrease from said pre-selected high “
B”
frequency to said pre-selected low “
A”
frequency,timing circuit means for timing a pre-selected time interval between the locking and unlocking periods of said phase lock detector circuit means and coupled to the output signal for said phase lock detector for initiating the timing period upon detection of a locking frequency, a binary coded decimal counter having input terminals and binary coded decimal output terminals, an input terminal for said counter being coupled to be responsive to said output signal for said phase lock detector upon receipt of a locking signal frequency for enabling said counter to count up, said output terminals for said counter providing binary coded decimal signals representative of the counters'"'"' count, said counter having a pre-selected total decimal count, multiplexing circuit means coupled to pre-selected output terminals of said counter and to said ladder network and providing an individual output count signal corresponding to the decimal count of said counter in response to the receipt of said inputted binary coded decimal signals, and effective to serially select and add a corresponding resistor or resistors from said ladder network for defining a lower high “
B”
frequency as the input signals coupled to said detector circuit means decrease in frequency, the “
zero”
output count of the counter causing a pre-selected resistor of said ladder network to be continuously connected in combination with the frequency setting network for determining the pre-selected high frequency below said “
B”
frequency lockout frequency of said phase lock detector circuit means,the decreasing frequencies of the input siren signals causing said phase lock detector circuit means therefrom upon the unlocking thereof that is coupled to said counter input terminal and causes said counter to count up one decimal count for each lock-unlock sequence that occurs during the pre-selected time interval of said timing circuit and thereby causing an additional resistor or resistors to be added to said pre-selected resistor of said ladder network to said frequency setting network for defining a lower frequency for said detector circuit means, upon said counter counting up to said pre-selected count, the counter directly provides an output signal representative of the complete tracking of the siren signal from said pre-selected high “
B”
siren frequency to the low “
A”
frequency incrementally in accordance with the total decimal count selected for said counter, and means coupled to said output signal representative of the complete tracking of the siren signal from said “
B”
frequency to said “
A”
frequency for signaling the detection of a valid siren sound signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
- B”
-
8. A method of controlling the traffic control signals at an intersection of two roads to permit only an emergency vehicle to proceed through the intersection having the right of way due to the provision of a “
- green”
traffic signal for the emergency vehicle, mounting a siren sound sensor adjacent an intersection of at least two intersecting roads and providing electrical signals representative of the sound picked up by the microphone, said microphone being sensitive to emergency vehicle'"'"'s siren sounds emitted from an emergency vehicle, said microphone being oriented and axially arranged to receive the emergency vehicle siren sounds from an emergency vehicle approaching an intersection,mounting a plurality of similar siren sound sensors adjacent the intersection of said two roads similar to the first mentioned siren sound sensor whereby the intersection is monitored by four siren sound sensors spaced approximately 90 degrees apart for receiving siren sounds from an emergency vehicle approaching the intersection from different directions, each of said siren sound sensors comprising a microphone and acoustic horn arranged in a complimentary acoustic electronic arrangement that provides a tuned and directional audio sensor sensitive to the frequent range of the sound from an emergency vehicle'"'"'s siren, each of said acoustic horns and microphone having individual pre-amplifying circuit means and siren sensing electronic means and having the microphone facing in the direction of travel of an emergency vehicle approaching the intersection so that each acoustic horn-microphone siren sound sensor is facing 90 degrees from each other acoustic horn-microphone siren sound sensors at a typical four way intersection for monitoring emergency vehicles traveling north, south, east and west toward said intersection, said pre-amplifying circuit means for each individual acoustic horn-microphone combination receiving the siren sound signals from an individual microphone for the individual acoustic horn-microphone combination, said arrangement of pre-amplifying means and acoustic horn-microphone combinations will provide a dominant level of electrical output signals in response to the detected siren sounds emitted that are “
on axis”
with the emergency vehicle'"'"'s siren which is heading towards the intersection, said siren sensing electronic means for each individual amplifying means comprising phase lock loop detection means including filtering circuit means for the electronic signals received from an individual pre-amplifying means having a band pass for transmitting only the frequency signals comprising the siren signals frequency range to said electronic means,said phase lock loop detection means being adapted to lock to said filtered siren signals to lock onto a high “
B”
frequency to a low “
A”
frequency and unlock said detection means as said siren signals decrease in frequency,continuously adjusting the high “
B”
frequency of said detection means as said siren signals decrease in frequency between said high “
B”
frequency and low “
A”
frequency for detecting and tracking the locking and unlocking cycles of said detection means over the range of siren sound signals applied thereto, andcounting a pre-selected number of locking and unlocking cycles in response to the decreasing frequencies of said siren sound signals so that detection means that counts up to said pre-selected number first will finalize and lock out the other detection means and provide an output signal representative of a valid siren sound signal being detected.
- green”
Specification
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Current AssigneeJeffery I. Berlin, Robertt H. Cornett
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Original AssigneeJeffery I. Berlin, Robertt H. Cornett
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InventorsCornett, Robertt H., Berlin, Jeffery I.
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Primary Examiner(s)BLOUNT, ERIC
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Application NumberUS11/591,155Time in Patent Office1,896 DaysField of Search340/902US Class Current340/902CPC Class CodesG08G 1/087 Override of traffic control...G08G 1/0965 responding to signals from ...
