System and method for transmitting data in an optical traffic preemption system

• Main Author: HAMER; STEVEN M
• Format: Patent
• Language: English
• Published: 15.12.1992
• Subjects: ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; PHYSICS; SIGNALLING; TRAFFIC CONTROL SYSTEMS; TRANSMISSION

A method of optically transmitting data from an optical emitter to a detector mounted along a traffic route is used in an optical traffic preemption system. The method allows variable data to be transmitted in a stream of light pulses by interleaving data pulses between priority pulses. By allowing data to be transmitted in a stream of light pulses, an optical emitter constructed in accordance with the present invention transmits an optical signal that can include an identification code that uniquely identifies the emitter, an offset code that causes a phase selector to create a traffic signal offset, an operation code that causes traffic signal lights to assume at least one phase and a range setting code that causes a phase selector to set a threshold to which future optical transmissions will be compared. Phase selectors constructed in accordance with the present invention are provided with a discrimination algorithm which is able to track a plurality of optical transmissions with each detector channel. Optical emitters constructed in accordance with the present invention are provided with a coincidence avoidance mechanism which causes overlapping optical transmission from separate optical emitters to drift apart. The present invention provides an optical signal format that allows variable data to be transmitted, while maintaining compatibility with prior optical traffic preemption systems.