Patent attributes
Various approaches for activating a traffic control preemption system. The traffic control preemption system has a receiver with a photodetector and circuitry that produces a number of electrical pulses in response to each detected light pulse. For each detected light pulse the number of electrical pulses represents a level of radiant power of the light pulse. A threshold number of electrical pulses and an activation frequency at which the threshold number of electrical pulses is repeated activates preemption. Control circuitry is coupled to a light emitter and controls the light emitter to emit bursts of light pulses. Each burst includes at least two light pulses and the control circuitry controls the frequency of light pulses in each burst and the frequency of the bursts to cause the receiver to produce at least the threshold number of electrical pulses at the activation frequency and activate the preemption.
