| 摘要 |
An optical traffic preemption detector according to Figure 6 detects pulses of light emitted by an approaching emergency vehicle and provides an output signal which is processed by a phase selector. The phase selector can request a traffic signal controller to preempt a normal traffic signal sequence to give priority to the emergency vehicle. A detector assembly is mounted in proximity to an intersection and can have multiple detector channels. A detector channel can have multiple photocells. each photocell is provided with a rise time filter. If a detector channel has more than one photocell, the outputs of the respective rise time filters are coupled together. An output of a rise time filter, or coupled rise tame filters, is first applied to a current-to-voltage converter and then a band pass filter. The band pass filter isolates a decaying sinusoid signal from a signal representative of a pulse of light. The decaying sinusoid signal is processed to produce a detector channel output signal that has a number of pulses for each pulse of light.
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