| 摘要 |
A system for controlling traffic lights to clear intersections in advance of the approach of an emergency vehicle, in which a directional radio transmitter and antenna are provided on the vehicle, which transmits one or the other of two selected coded signals in the direction of movement of the vehicle. An omni-directional radio antenna and receiver are positioned at the intersection to receive the radiated signal from the vehicle approaching that intersection. The first coded signal includes a first pair of frequencies, and the second coded signal includes a different pair of frequencies, which are decoded by two similar pairs of filters. The signals cause a sequence of events including a closing of an interrupter relay which opens all circuits leading from the traffic light controller to all of the traffic lights, and controls the closing, alternately, of two sets of selected circuits, to apply power alternately to two selected sets of traffic lights.
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