Detection system for emergency vehicles with signal preemption means
First Claim
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1. Apparatus for indicating the presence of an emergency vehicle as distinguished from other non-emergency vehicles and the like comprising:
- means for generating an identifiable alternating magnetic field that radiates from emergency vehicles with a predetermined, fixed frequency outside the frequency band of alternating magnetic fields surrounding non-emergency vehicles in the 90 Hz to 6 KHz frequency band associated with the pulsating ripple DC current flowing in an electrical system and metallic mass of all motor-driven objects having a rotational electrical generating device driven by the motor to supply necessary current to drive the electrical system of the motor-driven object when the motor of the motor-driven object is operative;
means for detecting the identifiable alternating magnetic field radiating from emergency vehicles with a predetermined frequency as that of an emergency vehicle as distinguished from alternating magnetic fields in the 90 Hz to 6 KHz band radiating from all motor-driven objects generated by pulsating DC current supplied to the electrical system of the motor-driven object by a rotational electrical device driven by the motor of the motor-driven object when the motor is operative;
said means for generating an identifiable alternating magnetic field radiating from an emergency vehicle comprising an AC current generator coupled through an output electrical circuit to an alternating magnetic field radiating source such as the metallic mass incorporated in the motor, body and frame of the emergency vehicle;
said AC current generator connected through a switch and input electrical circuit to a battery circuit of the emergency vehicle as a constant power source to drive an AC current generator which is connected through an output electrical circuit to cause current of a predetermined frequency to flow through the output circuit including body and frame of the emergency vehicle;
said means for detecting the identifiable alternating magnetic field radiating from emergency vehicles with a predetermined frequency comprising means for coupling said detection means to the identifiable changing magnetic field radiated by a flow of alternating current in said AC current generator output circuit installed on emergency vehicles for the purpose of identification;
said coupling means comprising a signal developing means and an electric probe connected through an electrical connection to the input of said signal developing means to continuously detect the presence of an emergency vehicle in close proximity to said coupling means independently of whether the emergency vehicle is in motion;
said signal developing means comprising an electrical filter, signal amplification means, signal detection means and an indicating means all connected in sequence;
said detection means converts the AC signal to a voltage level suitable to drive the indicating means which indicates the presence of an emergency vehicle at said electrical probe.
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Abstract
A system for detecting emergency vehicles and providing an apparatus for preempting traffic signals at intersecting streets to assure right-of-way in the direction of travel of emergency vehicles. The apparatus or system includes an alternating current generator installed on emergency vehicles to generate an alternating magnetic field surrounding the vehicle at a frequency or coded frequencies reserved for emergency vehicles and an emergency vehicle detection system which detects only alternating magnetic fields with a frequency or coded frequencies radiated by emergency vehicles.
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Citations
13 Claims
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1. Apparatus for indicating the presence of an emergency vehicle as distinguished from other non-emergency vehicles and the like comprising:
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means for generating an identifiable alternating magnetic field that radiates from emergency vehicles with a predetermined, fixed frequency outside the frequency band of alternating magnetic fields surrounding non-emergency vehicles in the 90 Hz to 6 KHz frequency band associated with the pulsating ripple DC current flowing in an electrical system and metallic mass of all motor-driven objects having a rotational electrical generating device driven by the motor to supply necessary current to drive the electrical system of the motor-driven object when the motor of the motor-driven object is operative; means for detecting the identifiable alternating magnetic field radiating from emergency vehicles with a predetermined frequency as that of an emergency vehicle as distinguished from alternating magnetic fields in the 90 Hz to 6 KHz band radiating from all motor-driven objects generated by pulsating DC current supplied to the electrical system of the motor-driven object by a rotational electrical device driven by the motor of the motor-driven object when the motor is operative; said means for generating an identifiable alternating magnetic field radiating from an emergency vehicle comprising an AC current generator coupled through an output electrical circuit to an alternating magnetic field radiating source such as the metallic mass incorporated in the motor, body and frame of the emergency vehicle; said AC current generator connected through a switch and input electrical circuit to a battery circuit of the emergency vehicle as a constant power source to drive an AC current generator which is connected through an output electrical circuit to cause current of a predetermined frequency to flow through the output circuit including body and frame of the emergency vehicle; said means for detecting the identifiable alternating magnetic field radiating from emergency vehicles with a predetermined frequency comprising means for coupling said detection means to the identifiable changing magnetic field radiated by a flow of alternating current in said AC current generator output circuit installed on emergency vehicles for the purpose of identification; said coupling means comprising a signal developing means and an electric probe connected through an electrical connection to the input of said signal developing means to continuously detect the presence of an emergency vehicle in close proximity to said coupling means independently of whether the emergency vehicle is in motion; said signal developing means comprising an electrical filter, signal amplification means, signal detection means and an indicating means all connected in sequence; said detection means converts the AC signal to a voltage level suitable to drive the indicating means which indicates the presence of an emergency vehicle at said electrical probe. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification